Article

Fouling characterization of camel milk with comparison to bovine milk

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Abstract

The fouling behavior of raw camel milk was studied under controlled surface temperatures (71–79 °C) and shear stresses (0.03–3.14 Pa) using a spinning disc apparatus. Camel milk fouling decreased with increasing shear and increased significantly as surface temperature increased. Comparing to bovine milk, camel milk had approximately 76% lower linear fouling rates, and 55% lower final fouling resistances, however, the masses of their dry deposits were not significantly different. Micro-CT scan images revealed a higher porosity of the deposit of camel milk (76%) than bovine milk (55%), which resulted in the lower thermal resistances observed during camel milk fouling. Composition analysis showed that fat (52–62%) and protein (34–43%) were the major constituents in both deposits. SDS-PAGE analysis indicated that casein, α-lactalbumin, serum albumin and peptidoglycan recognition protein were the major proteins contributing to the deposition of camel milk, while β-lactoglobulin and casein were responsible for bovine milk fouling.

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... The effects of pasteurization on the fouling behavior of raw camel milk have been evaluated; this thermal treatment resulted in reduced fouling [49]. The protein profiles are very different among dairy cows' and camel milk, as follows: β-lactoglobulin, the main factor in cows' milk fouling, is not present in camel milk, while caseins, α-lactalbumin, serum albumin and peptidoglycan are responsible for camel milk fouling. ...
... The protein profiles are very different among dairy cows' and camel milk, as follows: β-lactoglobulin, the main factor in cows' milk fouling, is not present in camel milk, while caseins, α-lactalbumin, serum albumin and peptidoglycan are responsible for camel milk fouling. Camel milk showed a lower fouling resistance compared to cows' milk, forming more porous deposits [49]. The effects of camel milk thermal treatments using high temperatures must be evaluated in further experiments, in order to determine camel milk therapeutic characteristics in raw, pasteurized and sterilized milk. ...
Article
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Milk is considered a complete food because all of the nutrients important to fulfill a newborn’s daily requirements are present, including vitamins and minerals, ensuring the correct growth rate. A large amount of global milk production is represented by cow, goat, and sheep milks; these species produce about 87% of the milk available all over the world. However, the milk obtained by minor dairy animal species is a basic food and an important family business in several parts of the world. Milk nutritional properties from a wide range of minor dairy animal species have not been totally determined. Hot temperatures and the lack of water and feed in some arid and semi-arid areas negatively affect dairy cows; in these countries, milk supply for local nomadic populations is provided by camels and dromedaries. The nutritional quality in the milk obtained from South American camelids has still not been completely investigated, the possibility of creating an economic resource for the people living in the Andean highlands must be evaluated. Both mare and donkey milks show a chemical composition very similar to human milk, and they represent a good replacer of cows’ milk for infants nutrition, especially for children affected by cow milk proteins allergy. In this review, differences and similarities in the quality parameters of milk from minor dairy animals, such as camelids and equids, have been compared.
... C amel milk has been an important source of nutrition for nomadic and pastoral cultures in the arid parts of the world for centuries. More recently, there has been a growing interest in camel milk as an alternative to bovine milk and nutraceutical products because of its high nutritional value and therapeutic effects (Zhang et al., 2020). In Pakistan particularly desert regions of the Sindh, Punjab and Baluchistan around 0.8 million of camels are slaughtered in summer season (Anonymous, 2002). ...
... Recently, various researches showed that the remedial assets were due to certain types of constituent in milk of camel (Nora et al., 2014). Meanwhile, nowadays milk of camel is used worldwide, but it is not the primary choice for the peoples because its taste is salty (Zhang et al., 2020;Sisay and Awoke, 2015). Though, it has numerous useful assets as it is used for the treatment for autism, allergy, diabetes and also stops liver cirrhosis. ...
Article
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Milk is a complete diet for the human beings because it comprises all the supplements, such as water, fat, carbohydrates, lactose, protein, minerals, nutrients and catalysts. A total of 20 % milk is obtained from different species including sheep, ass, horse, yak, goat, bison and camel while the 80 % milk is produced by cows. Milk of camel plays an essential part in the diet of human. Additionally, camel milk comprises numerous fatty acids and enzymes. Hence camel milk has many beneficial effects, such as antiviral, antibacterial, anti-diabetic, anti-carcinogenic and anti-ageing. Besides, camel milk contains abundant proteins which are conductive to improve the immunity functions. Thus, it is necessary to illuminate the beneficial impact of camel milk and its composition.
... Freeze drying technique was used to analyze the thermal characteristics of camel milk and its principal components in the first recorded trial aiming at creating camel milk powder (Zhang et al., 2020). These tests, however, were conducted in a laboratory (rather than on an industrial scale) using a freeze-dryer that allowed drying at temperatures ranging from -40 to 20 °C under a vacuum of 100 pounds per square inch. ...
Chapter
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Camel milk is a relative newcomer to both Indian and as well to international milk markets. The recent processing technology emergence has coincided with a variety of processed products based on technology established for milk from other dairy animals. Technical improvements, on the other hand, have to be tailored to a functional food product with a distinct behavior and composition. Camel milk powder can provide a great opportunity to dairy industries for introducing new products to the market of milk and milk products. This article gives a brief overcome.
... • Produced powder is found to be stable (Zhang et al., 2020). • Launched camel milk powder and camel milk icecream in 2020. ...
Presentation
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The dairy industry could take advantage of camel milk to use the animals for milk production rather than as cargo carriers. The powder is a good way to increase the shelf life of milk, and by using camel milk powder, camels may be used and a source of milk other than cow and buffalo can be obtained by the dairy. Additionally, camel milk has a number of health advantages over cow milk, some of which go above and beyond expectations. Therefore, using camels and their milk can best be accomplished using camel milk.
... Freeze drying technique was used to analyze the thermal characteristics of camel milk and its principal components in the first recorded trial aiming at creating camel milk powder [6] . These tests, however, were conducted in a laboratory (rather than on an industrial scale) using a freeze-dryer that allowed drying at temperatures ranging from -40 to 20°C under a vacuum of 100 pounds per square inch. ...
Article
Full-text available
Camel milk is a relative newcomer to both Indian and as well to international milk markets. The recent processing technology emergence has coincided with a variety of processed products based on technology established for milk from other dairy animals. Technical improvements, on the other hand, have to be tailored to functional food products with a distinct behavior and composition. Camel milk powder can provide a great opportunity to dairy industries for introducing new products to the market of milk and milk products. This article gives a brief review regarding camel milk powder development technology, limitations and challenges to overcome.
... Freeze drying technique was used to analyze the thermal characteristics of camel milk and its principal components in the first recorded trial aiming at creating camel milk powder [6] . These tests, however, were conducted in a laboratory (rather than on an industrial scale) using a freeze-dryer that allowed drying at temperatures ranging from -40 to 20°C under a vacuum of 100 pounds per square inch. ...
... Thus, alcohol testing was extremely useful to the global dairy industry since it allowed acidic milk, such as colostrum or mastic milk, to be processed without causing quality issues or coagulation in the dairy pasteurizer's heating plates [13]. Much attention has been devoted to the heat stability of camel milk in recent years [14], but there is relatively little published information on the effects of ethanol on camel milk protein stability. ...
Article
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This research was carried out to study the variation in ethanol stability and chemical composition of five camel milk samples, including two pasteurized samples (Alwatania and Darir alabaker) and three raw samples (Majaheim, Wadah, and Hamra). Ethanol stability was analyzed by dispersing camel milk samples with 0 to 100% ethanol (v/v). The findings indicate that camel milk samples precipitated after adding an equal volume of ethanol at concentrations between 50% and 64% ethanol, depending on the milk sample. The addition of sodium chloride at different concentrations (1–10%) to camel milk resulted in a significant increase in ethanol stability, and samples from Majaheim and Alwatania exhibited the highest ethanol stability values (88%). In contrast, the addition of EDTA to camel milk for pH ranging between 5.9 and 7.1 has increased ethanol stability with a sigmoidal shape in camel milk. The largest ethanol stability differences were observed in a camel milk sample from Alwatania. Thus, the level of Ca2+ in camel milk may contribute to ethanol stability by shifting the entire profile to higher ethanol stability values. The chemical composition of different camel samples was also determined. The lactose content of camel milk varied significantly (p < 0.05) across samples, ranging from 4.37% in Majaheim camel milk to 4.87% in Alwatania camel milk. The total solids of camel milk varied significantly between raw and pasteurized samples, ranging between 10.17% and 12.10%. Furthermore, protein concentration in camel milk obtained from different camel samples varied, from 2.43% to 3.23% for Hamra and Alwatania, respectively. In conclusion, ethanol stability in camel milk was dependent on the camel breed, pH level, ionic strength, and EDTA addition.
... Thus, alcohol test was extremely useful to the global dairy industry since it allowed acidic milk, such as colostrum or mastic milk, to be processed without causing quality issues or coagulation in the dairy pasteurizer's heating plates [12]. Much attention has been devoted to the heat stability of camel milk in recent years [11], but there is relatively little published information on the effects of ethanol on camel milk protein stability. ...
Preprint
Simple Summary: Camel milk has recently gained the interest of consumers and the dairy industry, as it is widely suggested as an ideal substitute for cow milk. The nutritional value and the bioactivity of camel milk proteins have received particular attention from research groups and industrial companies around the world. Camel milk proteins can be used as ingredients in the manufacturing and stabilization of foods and beverages; however, in these applications, controlled aggregation of milk proteins and stability at high temperatures and in alcohol is desirable. Ethanol stability of milk could be used as an indicator of its freshness and provide information on the stability of raw milk ultra-high temperatures and powder processing. Abstract: This research was carried out to study the variation in ethanol stability and chemical composition of five camel milk samples including two pasteurized samples (Alwatania and Darir ala-baker) and three raw samples (Majaheim, Wadah, and Hamra). Ethanol stability were analyzed by dispersing camel milk samples with 0 to 100% ethanol (vol/vol). Findings indicate that camel milk samples precipitated after adding an equal volume of ethanol at concentrations between 50% and 64% ethanol, depending on milk sample. The addition of sodium chloride at different concentrations (1-10%) to camel milk resulted in a significant increase in ethanol stability and samples from Majaheim and Alwatania exhibited the highest ethanol stability values (88%). In contrast, the addition of EDTA to camel milk for pH ranging between 5.9-7.1 has increased ethanol stability with a sigmoidal shape in camel milk. The largest ethanol stability differences were observed in camel milk sample from Alwatania. Thus, the level of Ca 2+ in camel milk may contribute to ethanol stability by shifting the entire profile to higher ethanol stability values. The chemical composition of different camel samples was also determined. Lactose content of camel milk varied significantly (p < 0.05) across samples, ranging from 4.37% in Majaheim camel milk to 4.87% in Alwatania camel milk. The total solids of camel milk varied significantly between raw and pasteurized samples, ranging between 10.17% and 12.10%. Furthermore, protein concentration in camel milk obtained from different camel samples varied, from 2.43% to 3.23% for Hamra and Alwatania, respectively. In conclusion , ethanol stability in camel milk was dependent on the camel breed, pH level, ionic strength, and EDTA addition. Citation: Alhaj, O.A.; Lajnaf, R.; Jrad, Z.; Alshuniaber, M.A.; Jahrami, H.A.; Serag El-Din, M.F.
... Camel milk has always represented an important food for nomadic people in the arid parts of the world; recently, camel milk attracted great attention as a possible replacer to dairy cow's milk because of its therapeutic effects [4]. The use of alternative milk for feeding children can be effective in reducing the development of gastrointestinal disorders [5]. ...
Article
Full-text available
In most areas of the world, camelids are considered exotic animals, living only in zoological gardens. Additionally, considering the original lands where they were previously bred with specific economic and social aims, today it is possible to detect a reduction in their total numbers. Typically bred as working animals for goods transportation in desert regions, and as a source of meat and milk, in recent years, camels have been dismissed due to the construction of new roads for motor vehicles, the migration of nomadic populations from deserts to urban zones, and the choice of some autochthonous bovine breeds as sources of meat and milk. The decline in camelids heads seems irreversible. Camels should be considered a valid source of food in marginal areas; the peculiar quality parameters of their milk, showing the proper characteristics for the use of this milk in human nutrition, can justify the choice for breeding them, rather than considering camels only as objects of amusement.
... However, in some countries, camel milk is consumed directly unprocessed; therefore there is a need of thermal treatment (pasteurization) on milk for ensuring product safety and prolonging its shelf life (Felfoul, Lopez, Gaucheron, Attia, & Ayadi, 2015a) that can overcome the deposit formation occurring during thermal processing called fouling (Bansal & Chen, 2006;Felfoul, Lopez, Gaucheron, Attia, & Ayadi, 2015b). In this regard, a recent study focused on chemical composition and protein profile of the camel milk fouling deposits that were compared with bovine milk deposits using SDS-PAGE analysis, to identify the proteins that contribute to the deposition of camel milk and provide fundamental insights to apply the mitigation methods existing for bovine milk fouling and further applications to camel milk processing (Zhang, Xu, Villalobos-Santeli, & Huang, 2020). Camel milk caseinÀoriginated bioactive peptides (Jrad et al., 2014) can be used as valuable ingredients in formulation of functional foods with health-promoting properties due to their therapeutic and preventive activities. ...
Chapter
Milk and dairy products with their distinct composition of carbohydrates, proteins, fats, and micronutrients are purported to have beneficial effects on human health. They have the potential to enhance exercise performance and recovery and are considered functional sport foods/beverages. This chapter summarizes the current evidence regarding the benefits of dairy products on endurance and resistance exercise, as well as the potential to augment health and performance in a variety of populations including team sport athletes, exercising children and adolescents, and aging adults. The impact of dairy products on weight loss and sleep quality is also discussed.
... However, in some countries, camel milk is consumed directly unprocessed; therefore there is a need of thermal treatment (pasteurization) on milk for ensuring product safety and prolonging its shelf life (Felfoul, Lopez, Gaucheron, Attia, & Ayadi, 2015a) that can overcome the deposit formation occurring during thermal processing called fouling (Bansal & Chen, 2006;Felfoul, Lopez, Gaucheron, Attia, & Ayadi, 2015b). In this regard, a recent study focused on chemical composition and protein profile of the camel milk fouling deposits that were compared with bovine milk deposits using SDS-PAGE analysis, to identify the proteins that contribute to the deposition of camel milk and provide fundamental insights to apply the mitigation methods existing for bovine milk fouling and further applications to camel milk processing (Zhang, Xu, Villalobos-Santeli, & Huang, 2020). Camel milk caseinÀoriginated bioactive peptides (Jrad et al., 2014) can be used as valuable ingredients in formulation of functional foods with health-promoting properties due to their therapeutic and preventive activities. ...
Chapter
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Predictive microbiology aims to evaluate the effect of processing, distribution, and storage operations on microbiological food safety. It is based upon the premise that the response of population of microorganisms to environmental factors are reproducible, and that, by characterizing the environment in terms of identifiable, dominant factors controlling growth responses, it is possible, from past observations, to predict the responses of those microorganisms in other, similar environments. Predictive microbiology models represent the microbial responses to the environment. They are based mainly on observations made in synthetic culture media. Models cannot take into account all factors that may affect the microbial growth but select the most influential factors and only model their effects. The main assumptions of predictive microbiology and risk analysis are discussed in the present chapter. Moreover, the classification of predictive models and application in dairy processing are given. Finally, a case study using the tertiary model Sym’Previus software is presented.
... The first reported trial aimed at making camel milk powder was recent, where freezedrying technology was implemented to study the thermal characteristics of camel milk and its main components [7]. However, these tests were carried out in a laboratory (not at an industrial scale) with a freeze-dryer, allowing drying from −40 to 20 • C with a vacuum of 100 Pa. ...
Article
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The camel milk market was limited for a long time by its almost exclusive self�consumption use in nomadic camps. Significant development has been observed for the past two or three decades, including internationally, boosted by its reputation regarding its health effects for regular consumers. Such emergence has led the stakeholders in the sector to offer diversified prod�ucts corresponding to the tastes of increasingly urbanized consumers, more sensitive to “modern” products. Thus, traditionally drunk in raw or naturally fermented form, camel milk has undergone unprecedented transformations such as pasteurization, directed fermentation, cheese or yoghurt processing, and manufacture of milk powder for the export market. However, the specific character�istics of this milk (composition, physical properties) mean that the technologies applied (copied from technologies used for cow milk) must be adapted. In this review, some technological innovations are presented, enabling stakeholders of the camel milk sector to satisfy the demand of manufacturers and consumer
... Furthermore, other operating conditions could impact fouling occurrence. For example, in dairy pasteurization, the temperature profile plays the most important effect in fouling by being a key factor in protein denaturation and consequent deposition [4,6]. ...
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Biofouling is the unwanted accumulation of deposits on surfaces, composed by organic and inorganic particles and (micro)organisms. Its occurrence in industrial equipment is responsible for several drawbacks related to operation and maintenance costs, reduction of process safety and product quality, and putative outbreaks of pathogens. The understanding on the role of operating conditions in biofouling development highlights the hydrodynamic conditions as key parameter. In general, (bio)fouling occurs in a higher extension when laminar flow conditions are used. However, the characteristics and resilience of biofouling are highly dependent on the hydrodynamic conditions under which it is developed, with turbulent conditions being associated to recalcitrant biodeposits. In industrial settings like heat exchangers, fluid distribution networks and stirred tanks, hydrodynamics play a dual function, affecting the process effectiveness while favouring biofouling formation. This review summarizes the hydrodynamics played in conventional industrial settings and provides an overview on the relevance of hydrodynamic conditions in biofouling development as well as in the effectiveness of industrial processes.
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The aim of this study is to identify the chemical composition and the microstructure of the deposits obtained after heating camel and cow milks at 80 °C for 60 min using a laboratory scale device. Like cow milk, camel milk was affected by heat treatment with the reduction of the non-casein nitrogen content reflecting the denaturation of camel whey proteins. The composition of the deposits generated during heating camel and cow milks at 80 °C for 60 min revealed that while camel deposit contained 57 % w/w protein, cow deposit showed a higher protein content of 69 % w/w. The minerals content was 35 % (w/w) for camel deposit which was higher than that of cow sample, which was 28 % w/w. SEM of both deposits showed a familiar structure of a protein deposit with large clumps composed of smaller aggregates. Camel deposit showed an amorphous structure due to its deficiency in β-lactoglobulin.
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Introduction: Camel milk is the closest to a human mother's milk. Camel milk is different from other milks, however, having low sugar and cholesterol, high minerals (sodium, potassium, iron, copper, zinc and magnesium, and vitamin C). The milk is considered have medicinal characteristics as well. This systematic review is aimed at determining and reporting nutritional values and medicinal characteristics of camel milk in children. Methods: The search strategy of the current review is "(camel AND milk) AND (autism OR food allergy OR milk allergy OR children OR diarrhea." The search was conducted via PubMed, Scopus, and Google scholar. Also two Persian scientific databases (SID and Iranmedex) and international congresses were investigated. Full-text papers and abstracts on the topic of camel milk, evaluating nutritional value and medicinal properties, were included in this systematic review. Results: Out of the 472 records found in the resources, 35 related studies were included in the final analysis. The result showed that camel milk is highly nutritious and is safe for consumption by children. Conclusion: It seems that many researchers did not follow a specific guideline for reporting and confirming the therapeutic properties of camel milk in children, but there is evidence denoting the importance, trials, and investigations of its usability and benefits. Camel milk as a supplemental treatment seems less invasive and costly than specialist care, medications, alternative treatments, and behavioral interventions. Based on our findings, camel milk is safer for children, effective in the treatment of autism, improves general well-being, promotes body natural defenses, is a good nutritional source, and can helps the daily nutritional needs of humans.
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The deposition behaviour of the main components of milk fouling (β-lactoglobulin and calcium phosphate) and its dependence on the surface energy properties of the fouling support were evaluated in this work. As deposition supports, several modified stainless-steel materials obtained by surface modification techniques were used. Four fouling systems were analysed: an aqueous solution that resembles the mineral composition of milk (simulated milk ultrafiltrate, SMUF), at 44 and 70 °C, and SMUF with addition of β-lactoglobulin at 50 and 85 °C. Both the final amount of deposits formed for each system on the different surfaces and the type of aggregates formed during the first stages of the process for each case were assessed. The number and size of the calcium phosphate aggregates initially formed can be used as a predictive approach to the final amount of deposit developed for each system since relationships between these parameters were established.
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Diss. no. 12947 techn. sc. SFIT Zurich. Literaturverz.
Conference Paper
Approximately 80% of the production costs in the dairy industry are related to fouling and cleaning of process equipment. Costs are related to product quality, process efficiency and energy. Application of predictive fouling models has resulted in cost reduction from 30% to 80%. At present these fouling models are usually only applied off-line for a standard situation but in practice processing conditions change constantly, e.g. different composition of different batches of raw material, fluctuating capacities and equipment changes. All these changes affect fouling on a day to day basis. A further reduction of processing costs can be achieved via in-line control of fouling. Based on the existing fouling models, with proven effect in cost reduction, a model-based advanced control system has been developed for the in-line control of product quality and fouling. Tests of the system on a pilot-scale pasteuriser indicated that a reasonable cost reduction could be achieved. A future challenge will be the combination of the model-based control system with an in-line monitoring system for cleaning, making a total optimisation of processing and cleaning possible.
Article
Fouling is a serious problem in food processing especially in dairy industry. Sugar as a sweetener is very commonly added in various dairy products, however, severe fouling is found in on-site operations when processing sweetened dairy products. While milk fouling has been studied extensively, the compositional effect of sugar in dairy products on their fouling is still elusive. Here, we investigated the effect of different sugars (glucose, fructose and sucrose) on the fouling behavior of whey protein. Fouling formations were conducted using model solutions consisting of whey protein isolate (WPI) and sugars in a spinning disc apparatus under well-controlled temperatures and shear stresses. We found that, WPI fouling was reduced for the solutions with 10 wt% of sugar added by more than 30% in terms of fouling resistance and deposit mass, regardless of the type of sugar. We postulate that this reduction was because of the stabilizing effect of sugar on WPI, which was confirmed experimentally by the increased denaturation and aggregation temperatures of whey protein in the sugar-added WPI solutions. Increasing shear stress reduced the fouling of all test solutions, but no deposit sloughing was observed for the sugar-added WPI solutions. The addition of sugar in WPI solution also affected the composition and morphology of the deposits, which had lower protein in content and higher porosity in structure.
Chapter
This chapter discusses the problem of fouling in dairy processes, its mitigation and removal. The mechanism of fouling is described in terms of three major steps: activation, transport to the equipment surface and attachment. The most active component in thermal fouling by milk is β-lactoglobulin but other components that are less easily activated or even normally inactive such as caseins and fat can be incorporated in the fouling process when the quality of milk is poor because of high acidity or contamination by microbial enzymes. Other major factors affecting the rate and amount of fouling are the temperature, the pressure, the amount of gases released, the local flow velocity, the geometry of the equipment, the condition of the equipment surface and the start-up procedure of the heat exchanger. Keywords: Fouling, Cleaning-in-place, β-lactoglobulin, casein, fat, pressure, air bubbles, flow velocity, start-up.
Article
Drinking non-bovine milk has been reported to possess bio-functionality for regular consumers. Camel milk is a traditional product that has been used for many years in arid rural communities of Asia and Africa as a biomedicine to cure several health issues such as asthma, oedema, and diabetes. The product consists of appropriate amounts of bioactive compounds. In addition, it contains low amounts of fatty acids and cholesterol, whilst it does not contain β-lactoglobulin. The latter, which is present in bovine milk, causes allergic symptoms in some people. The similarity of the formula to human milk suggests this superfood as an alternative for bovine milk with complete nutrition for infants. In this review, the biomolecules present in camel milk and their positive roles on the health of consumers are extensively discussed.
Article
This review summarises current knowledge on camel milk proteins, with focus on significant peculiarities in protein composition and molecular properties. Camel milk is traditionally consumed as a fresh or naturally fermented product. Within the last couple of years, an increasing quantity is being processed in dairy plants, and a number of consumer products have been marketed. A better understanding of the technological and functional properties, as required for product improvement, has been gained in the past years. Absence of the whey protein β-LG and a low proportion of к-casein cause differences in relation to dairy processing. In addition to the technological properties, there are also implications for human nutrition and camel milk proteins are of interest for applications in infant foods, for food preservation and in functional foods. Proposed health benefits include inhibition of the angiotensin converting enzyme, antimicrobial and antioxidant properties as well as an antidiabetogenic effect. Detailed investigations on foaming, gelation and solubility as well as technological consequences of processing should be investigated further for the improvement of camel milk utilisation in the near future.
Article
Using a developed laboratory scale device, different heat treatment conditions were applied on camel and cow wheys. After each deposition experiment, photos of stainless steel plates were taken and dry deposit weights were determined. Proteins denaturation was studied by electrophoresis (SDS-PAGE) and differential scanning calorimetry (DSC). The obtained results have shown that heating both cow and camel wheys at 60 °C does not generate deposit. Furthermore, the heat treatment at above 70 °C was found to cause a severe fouling of stainless steel plate. The electrophoresis patterns indicated that heating at 90 °C caused camel serum albumin's (CSA) band disappearance for both rennet and acid wheys. However, α-lactalbumin's (α-la) concentration decreased versus temperature and heating time. DSC thermograms showed that denaturation temperatures were 73.8 °C for camel rennet whey, 60.5 °C for camel acid whey, 70.5 °C for cow rennet whey and 63.9 °C for cow acid whey. Taken into the count the absence of β-lg in camel milk and based on the obtained results several hypotheses were advanced to explain camel milk fouling during heat treatment.
Article
Using a developed laboratory scale device, different heat treatment conditions were applied on camel and cow milks. After each fouling experiment, photos of stainless steel plates were taken and dry deposit weights were determined. The thermal behaviour of camel and cow proteins was studied by electrophoresis (SDS-PAGE), differential scanning calorimetry (DSC) and free thiol groups concentrations evolution. The obtained results have shown that heating both camel and cow milks at 70°C for 2h generate deposit formation. The fouling rate was more important when heating camel milk than after heating cow milk for all heat conditions except at 90°C for 2h. Electrophoresis patterns indicated that after heating camel milk at 90°C, α-lactalbumin (α-la), camel serum albumin (CSA) and κ-casein bands decreased. Bovine serum albumin (BSA) disappear from the electrophoresis patterns after heating cow milk at 70°C while β-lactoglobulin (β-lg) and α-la bands disappeared only at 90°C. DSC thermograms of camel milk showed that the denaturation temperature of camel proteins is 77.8°C, lower than that of cow proteins which is 81.7°C. The results of free thiol groups evolution versus temperature and heating time showed that camel proteins denaturation starts between 70 and 80°C. However, for cow milk, the whole denaturation phenomenon happens after heat treatment at 70°C for 30min.
Article
In this work, we investigated the role of four independent process parameters, namely product temperature at the heat exchanger outlet, mean residence time, temperature increase between the heat exchanger inlet and outlet, and heat effectiveness, in the protein denaturation, aggregation, and fouling of a beta-lactoglobulin (beta-lg) concentrate that was chosen as model fluid for milk derivatives. A pilot scale plate heat exchanger in countercurrent configuration, supplied with a holder, was used in order to mimic industrial process conditions. The denaturation level and aggregates size of the heat treated beta-lg concentrate at the exchanger and holder outlets, along with the fouling mass in the plate heat exchanger were simultaneously determined. The results indicated that beta-lg denaturation, aggregation, and fouling reactions were mainly governed by the temperature profile in the investigated range of operating conditions, even though a small influence of residence time and healing rate was highlighted in the less denaturing conditions. A dimensional analysis was performed to identify the key dimensionless numbers governing beta-lg denaturation, aggregation, and fouling mechanisms in the heat treatment of a beta-lg concentrate. This allowed to emphasise the major influence of the Arrhenius exponential factor of beta-lg unfolding reaction, both related to temperature and beta-lg reactivity. The first Damkohler and Reynolds numbers, related to residence time and hydrodynamic conditions in the heat exchanger, as well as the heat exchange process parameters, linked to the heat effectiveness and the bulk-wall temperature differences, had also a small impact on beta-lg chemical behaviour. Moreover, empirical relationships based only on the Arrhenius exponential factor of beta-lg unfolding reaction permitted to describe the main trends observed in denaturation levels, aggregate sizes, and fouling masses, which underlined the predominant role of temperature and beta-lg reactivity in the investigated operating conditions. This study outlines finally that fast heat treatments permit to minimise fouling issues.
Article
Abstract Heat exchanger performance degrades rapidly during operation due to formation of deposits on heat transfer surfaces which ultimately reduces service life of the equipment. Due to scaling product deteriorates which causes lack of proper heating. Chemistry of milk scaling is qualitatively understood and the mathematical models for fouling at low temperatures have been produced but the behavior of systems at ultra high temperature processing has to be studied further to understand in depth. In diversified field the effect of whey protein fouling along with pressure drop in heat exchangers were conducted by many researchers. Adding additives, treatment of heat exchanger surfaces and changing of heat exchanger configurations are notable areas of investigation in milk fouling. The present review highlighted information about previous work on fouling, influencing parameters of fouling and its mitigation approach and ends up with recommendations for retardation of milk fouling and necessary measures to perform the task.
Article
Camel milk has traditionally been used to treat cancer, but this practice awaits scientific scrutiny, in particular its role in tumor angiogenesis, the key step involved in tumor growth and metastasis. We aimed to investigate the effects of camel milk on key components of inflammatory angiogenesis in sponge implant angiogenesis model. Polyester-polyurethane sponges, used as a framework for fibrovascular tissue growth, were implanted in Swiss albino mice and camel milk (25, 50 and 100 mg/kg/day) was administered for 14 days through installed cannula. The implants collected at day 14 post-implantation were processed for the assessment of hemoglobin (Hb), myeloperoxidase (MPO), N-acetylglucosaminidase (NAG), and collagen, which were used as indices for angiogenesis, neutrophil, and macrophage accumulation and extracellular matrix deposition, respectively. Relevant inflammatory, angiogenic, and fibrogenic cytokines were also determined. Camel milk treatment attenuated the main components of the fibrovascular tissue, wet weight, vascularization (Hb content), macrophage recruitment (NAG activity), collagen deposition and the levels of vascular endothelial growth factor (VEGF), interleukin (IL)-1β, IL-6, IL-17, tumor necrosis factor-α, and transforming growth factor-β. A regulatory function of camel milk on multiple parameters of the main components of inflammatory angiogenesis has been revealed, giving insight into the potential therapeutic benefit underlying the anti-cancer actions of camel milk.
Article
The problem of fouling from food fluids is very severe, leading to the need for rapid and effective cleaning. Fouling of the process plant happens as a result of complex processes that occur when a fluid is heated: protein and minerals are both deposited on the surface. This review describes research into both the engineering and the chemical factors that lead to deposition. Fouling can be modeled by using data for the thermal behavior of β-lactoglobulin, coupled with models for the flows and temperatures of the process plant. The rate of cleaning depends on both the deposit present and the type of chemical treatment used.
Article
The formation of immobile gels on heat transfer surfaces (‘coring’) caused by cooling fat solutions below their cloud point was studied using a novel spinning disc apparatus (SDA). The SDA features a cooled, removable heat transfer surface with well defined heat and mass transfer characteristics. Measurements of heat flux were combined with computational fluid dynamics simulations to yield reliable estimates of the surface temperature and shear stress. Fouling studies were performed with model solutions of 5 wt.% tripalmitin in a paraffin oil operating in the ‘cold start’ mode, wherein the experiment starts with the surface colder than the steady state, simulating one mode of operating a standard ‘cold finger’ experiment. Local heat flux measurements allowed the thermal fouling resistance to be monitored: deposit mass coverage and composition were also measured. The cold surface promotes the rapid formation of an initial gel layer, followed by a period of linear fouling, and finally falling rate fouling behaviour. The linear fouling rate was relatively insensitive to temperature and shear rate, while the fouling rate in the falling rate regime was found to depend on the temperature driving force for crystallisation kinetics. The solids fraction within the deposit layer increased over the duration of a 12 h fouling test, indicating rapid ageing. The rheological properties of the deposits were highly sensitive to solids fraction.
Article
Whey protein fouling deposits generated on the hot wall downstream a plate heat exchanger were analyzed by micro Raman spectroscopy (MRS) carried out in the 800–1800 cm−1 range. Deposits were formed using a model beta-lactoglobulin (BLG) fouling solution which was made using a whey protein isolate powder (89 wt.% in BLG) and a known amount of calcium. Thermal denaturation of the fouling solution was also analyzed by MRS as well as isolated BLG aggregates obtained by microfiltration of heated solutions. Specific Raman signatures of aggregates were identified, which were not detected in the Raman spectra of denatured (i.e. unfolded BLG molecule) solutions. MRS analyses at different depths of the deposit reveal a loss of α-helix structures, as observed in denatured BLG solutions, without the detection of aggregate signatures. For the range of calcium content investigated (from 97 to 160 mg l−1), no effect of calcium ions on the molecular conformation of BLG within the deposit was shown. Of great significance, results suggest that, for our set of operating conditions used, the mass distribution of the fouling deposit in a plate heat exchanger is primarily controlled by the distribution of the unfolded protein generated by the denaturation process.
Article
The heat-induced protein-protein interactions of alpha-lactalbumin (alpha-La) and bovine serum albumin (BSA), dispersed in a pH 6.8, 10% whey protein concentrates (WPC) permeate, were followed using alkaline and sodium dodecyl sulfate (SDS) 1D and 2D polyacrylamide gel electrophoresis (PAGE) and size-exclusion high-performance liquid chromatography (SE-HPLC). Heated (75 degrees C) 5% BSA solution contained large disulfide-bonded BSA aggregates, although some monomer BSA (SDS-monomeric BSA) could be dissociated from the aggregates by SDS. In contrast, similarly heated alpha-La solutions contained small quantities of several monomeric forms of alpha-La and dimeric alpha-La but no large aggregates. When 10% solutions of 1:1 (w/w) mixtures of alpha-la and BSA were heated, large disulfide-bonded aggregates and SDS-monomeric BSA and alpha-La were present. However, heated 2% mixtures contained more modified alpha-La monomers, alpha-La-dimers, and alpha-La-trimers, fewer large disulfide-bonded aggregates, and less SDS-monomeric alpha-La or BSA. These results suggest that BSA forms disulfide-bonded aggregates that contain available thiol groups that can catalyze the formation of differently structured alpha-La monomers, dimers, higher polymers, and adducts of alpha-La with BSA.
Article
The laminar-turbulent transition of three-dimensional boundary layers is critically reviewed for some typical axisymmetric bodies rotating in still fluid or in axial flow. The flow structures of the transition regions are visualized. The transition phenomena are driven by the compound of the Tollmien-Schlichting instability, the crossflow instability, and the centrifugal instability. Experimental evidence is provided relating the critical and transition Reynolds numbers, defined in terms of the local velocity and the boundary layer momentum thickness, to the local rotational speed ratio, defined as the ratio of the circumferential speed to the free-stream velocity at the outer edge of the boundary layer, for the rotating disk, the rotating cone, the rotating sphere and other rotating axisymmetric bodies. It is shown that the cross-sectional structure of spiral vortices appearing in the transition regions and the flow pattern of the following secondary instability in the case of the crossflow instability are clearly different than those in the case of the centrifugal instability.
Article
A two-dimensional dynamic fouling model for milk fouling in a plate heat exchanger (PHE) is proposed. Emphasis is placed on fouling prediction based on the hydrodynamic and thermodynamic performances of the PHE. A 12-channel PHE with counter-current flows is used in quantification of the milk deposition developed inside the channels. The aggregation rate of unfolded protein is found to increase exponentially with increasing wall temperature and is accompanied by a substantial reduction in the heat-transfer coefficient.
Article
The removal of films or deposits from dairy equipment used in the heating and holding of milk products often presents a serious problem. Parker and Johnson (1) early directed attention to the practical and sci- entific aspects of this problem. They defined milk film as the deposit which forms on metal heat-transfer surfaces due to the precipitating action of the heat alone. Milkstone was defined as the product resulting from the reaction between the milk film as described and the chemical constituents of the water supply and alkaline detergents applied or their end products. In commercial operations where milk products are heated, particularly above 140 ° F., by metal heat-transfer surfaces, there appears to be a daily film formation of some extent depending on the thermM differential and the type of equipment. This may vary from an extremely thin, trans- parent or translucent film appearing as a bluish or brown discoloration when viewed from an angle, on heater plates or tubes, to a heavy cheese- like blanket of milk solids on batch pasteurizing vats in which relatively rapid heating is accomplished by means of a high jacket temperature. Before an effort was made to determine the most suitable detergents or cleaning methods for hot-milk equipment, it was deemed advisable to study further the mechanism of the film formation on metal heat-transfer surfaces and to account, if possible, for some of the differences observed. EXPERIMENTS A simple apparatus was devised by means of which milk could be heated continuously under controlled conditions. The apparatus consisted of a 9-inch length of 2-inch stainless steel tubing stoppered on both ends with rubber stoppers. One stopper contained inlet and outlet tubes of 5 ram. I. D. glass tubing and a thermometer, of which only the bulb was extended on the inside. The inlet tube extended to within one inch of the bottom stopper. The outlet tube was flush with the inner surface of the top-retaining stopper. This assembly was placed vertically in an agi- tated, gas-heated water bath. The raw milk of 4 per cent fat content, fore- warmed to 85 ° F., was allowed to flow through the tube by gravity, being drawn off at the desired temperature through regulating the flow by means of a stop-cock on the inlet tube.
Article
A comprehensive review on Dromedary camel milk composition in comparison with bovine milk, the factors effecting camel milk composition, and an overview of production, properties, nutrition value, dairy products and functionality is provided. The mean values of camel milk composition reported from 1980 to 2009 are as follows: protein 3.1%; fat 3.5%; lactose 4.4%; ash 0.79% and total solids 11.9%. Differences between camel and bovine milk proteins lead to some difficulties in cheese manufacturing. Problems associated with cheese produced from camel milk, and factors reported to improve camel milk coagulation, are highlighted. Fresh and fermented camel milk were found to provide various potential health benefits including angiotension I-converting enzyme-inhibitory activity, hypocholesterolaemic effect, hypoglycaemic effect, antimicrobial and hypoallergenicity effects. The proposed mechanisms behind each health benefit are discussed.
Article
Fouling of heat exchangers is a problem in the dairy industry and costs billions of dollars every year. It has been studied extensively by researchers around the world, and a large number of studies are reported in the literature. This review focuses on the mechanisms of milk fouling, investigating the role of protein denaturation and aggregation as well as mass transfer. We also endeavor to review the effect of a number of factors which have been classified into 5 categories: (1) milk quality, (2) operating conditions, (3) type and characteristics of heat exchangers, (4) presence of microorganisms, and (5) transfer of location where fouling takes place. Different aspects have been discussed with the view of possible industrial applications and future direction for research. It may not be possible to alter the properties of milk since they are dependent on the source, collection schedule, season, and many other factors. Lowering the surface temperature and increasing the flow velocity tend to reduce fouling. Reducing the heat transfer surface roughness and wettability is likely to lower the tendency of the proteins to adsorb onto the surface. The use of newer technologies like microwave heating and ohmic heating is gaining momentum because these result in lower fouling; however, further research is required to realize their full potential. The presence of microorganisms creates problem. The situation gets worse when the microorganisms get released into the process stream. The location where fouling takes place is of paramount importance because controlling fouling within the heat exchanger may yield little benefit in case fouling starts taking place elsewhere in the plant.
Article
In milk fouling, the rate of production and composition of the fouled layer is controlled by reactions in the bulk fluid which lead to the creation of aggregates which are deposited on heated surfaces. The influences of temperature (70 °C–90 °C) and shear rate (111 s−1–625 s−1) upon the rate of growth and size of aggregates in whey protein concentrate solutions (WPC35) have been investigated using a Couette apparatus with and without the addition of mineral Calcium and Phosphorous. At temperatures below 75 °C, the aggregates formed are small and weakly bonded, whilst aggregates formed at higher temperatures (and higher shear rates) were denser and more rigid. This was attributed to weak van der Waals bonding between the particles at low temperatures and the formation of stronger covalent disulphide bonds at higher temperatures. Growth of the aggregates is due to both protein denaturation and aggregation; temperature step-change experiments have verified that denaturation is a strong function of temperature whilst aggregation is a function of the applied shear field and the strength of the particles. Step-changes in shear rate have shown that both denaturation and particle growth rate are enhanced by increasing shear rate due to an increase in the number of particle collisions, yet the final particle size showed a complex behaviour with the increase in shear rate. The addition of minerals to the WPC solution resulted in the formation of much smaller aggregates and increased deposition onto the surface of the Couette apparatus. This was attributed to interactions between Ca and β-lactoglobulin both in the bulk and at the heated surface.
Article
Food fouling is a severe industrial problem. Both the chemistry and fluid mechanics of fouling from milk fluids are complex. Experiments have been conducted in a tubular heat exchanger to determine whether fouling from whey protein concentrates is controlled by a bulk or a surface reaction. Results are interpreted in terms of a simple model, in which the amount of deposit is considered to be proportional to the volume of fluid that is hot enough to produce denatured and aggregated protein. The model fits the data reasonably well, and suggests bulk processes are important in whey protein fouling.
Article
Camel milk composition from both dromedary and Bactrian species was described in several publications. Eighty-two references from scientific journals or grey literature were selected, and a meta-analysis was achieved including the gross composition of camel milk (fat matter, total protein, lactose, ash and dry matter). A high variability was observed in the published data. Two factors were specifically studied: the geographical origin of the data and the year of publication. The references from Asia gave results with higher values in all the components, except ash, probably linked to the camel species, the Bactrian camel being predominant in the area. Milk composition reported in East African references was higher in fat matter content compared to other references in Africa and Western Asia. The chronicle made it possible to distinguish four periods according to fat matter and total protein values. Personal data from Kazakhstan showed significantly higher fat matter and total protein contents, but a lower lactose content compared to other references from Central Asia.
Article
Fouling of heat transfer equipment is a complex industrial problem. Many experiments have been carried out on a small scale to study the problem, but few models which can be used industrially have been developed. One problem may be that multiple mechanisms, often found in fouling, make scaleup very difficult. A series of possible scaleup strategies are tested using a computational model of a simple heat exchanger, and it is shown that, without a very good understanding of the basic mechanisms of fouling, scaleup may be very difficult in practice.
Article
The production of high-quality, safe foods is becoming more and more important. Therefore, mathematical models to predict product properties could greatly benefit the food industry, especially, if it would be possible to optimise the process of operation in relation to the desired product quality and safety. In general, three types of predictive models are necessary for optimisation and improvement of food production chains: (i) process models that describe the production chain in terms of model reactors; (ii) kinetic models that predict the transformation of food components and contaminants in food production chains; (iii) predictive models to estimate the costs related to process operation. Both the first and the last type of models were not yet available for the production of liquid food. With the support of the Netherlands Agency for Energy and the Environment and the Ministry of Agriculture, Nature and Fishery new predictive models have been developed. In this paper, the three types of models are presented and a general procedure for improvement of food production chains is discussed. The procedure developed for improvement of food production chains integrates the quality, safety and economic aspects. Cases demonstrate that the procedure enhances the development of new food products.
Article
A general overview is given of the main factors in the fouling of processing equipment used for heating dairy fluids. The data collected indicate that the primary step in fouling is the adsorption of a monolayer of proteins onto the wall of the heating equipment at room temperature. Real fouling (i.e., the formation of macroscopic layers of foulants), however, is caused by particle formation in the bulk of the liquid being processed. These particles include both whey protein aggregates and calcium phosphate particles. Their formation is heat induced, and the deposition takes place through diffusion toward the heating surface. Only very high flow rates are able to prevent their deposition and subsequent sticking. To better control the process of fouling, special attention is given to the parameters affecting the formation of both types of particles and how their formation can be retarded or prohibited, including the role of calcium sequestrants, pH, preheating, and flow rate herewith.
Article
Much research dealing with the processing of milk by-products in heat exchangers has noted the key role of calcium in β-lactoglobulin (β-LG) fouling behavior. Nevertheless, the manner by which Ca affects β-LG denaturation has rarely been quantified using reliable kinetic and thermodynamic data. To this end, the influence of Ca on β-LG denaturation mechanisms in simulated lactoserum concentrates was studied on the laboratory-scale under 100°C by HPLC analysis. The heat-treated solutions were composed of 53.3g/L β-LG and were enriched in Ca at various concentrations (0, 66, 132, and 264 mg/kg). The kinetic parameters (reaction order, activation energy, and frequency factor) associated with β-LG denaturation, along with the unfolding and aggregation thermodynamic parameters were deduced from these experiments and discussed with respect to Ca content. We found that the multistage process characterizing β-LG thermal denaturation is not greatly affected by Ca addition. In fact, the general model subdividing β-LG denaturation mechanisms in 2 steps, namely, unfolding and aggregation, remained valid for all tested Ca concentrations. The change in the predominant mechanism from unfolding to aggregation was observed at 80°C across the entire Ca concentration range. Moreover, the classical 1.5 reaction order value was unaffected by the presence of Ca. Interpretation of the acquired kinetic data showed that Ca addition led to a significant increase in kinetic rate, and more so in the aggregation temperature range. This indicates that Ca principally catalyzes β-LG aggregation, by lowering the Coulombian repulsion between the negatively charged β-LG reactive species, bridging β-LG proteins, or via an ion-specific conformational change. To a lesser extent, Ca favors β-LG unfolding, probably by disturbing the noncovalent binding network of native β-LG. Simultaneously, Ca has a slight protective role on the native and unfolded β-LG species, as shown by the increase in activation energy with Ca concentration. The calculation of thermodynamic parameters related to β-LG denaturation confirmed this observation. A threshold effect in Ca influence was noted in this study: no further significant kinetic rate change was observed above 132 mg/kg of Ca; at this concentration, the studied solution was an almost equimolar mixture of β-LG and Ca. Finally, we simulated the temporal evolution of β-LG species concentrations at diverse Ca contents at 3 holding temperatures. The simulations were based on the acquired kinetic parameters. This permitted us to highlight the greater effect of Ca on β-LG denaturation at high Ca content or for short-time heat treatments at temperatures near 100°C, as in heat exchangers.
Article
Hypoglycemic effect of camel milk supplementation in experimental rat model and significant reduction in doses of insulin in type 1 diabetic patients have been observed in our previous studies. This long-term study was undertaken to assess the efficacy, safety and acceptability of camel milk as an adjunct to insulin therapy in type 1 diabetics. In this 2-year randomized clinical, parallel design study, 24 type 1 diabetics were enrolled and divided into two groups. Group I (n=12) received usual care, that is, diet, exercise and insulin and Group II (n=12) received 500 ml camel milk in addition to the usual care. Insulin requirement was titrated weekly by blood glucose estimation. Results were analyzed by using the regression technique. In camel milk group, there was decrease in mean blood glucose (118.58±19-93.16±17.06 mg/dl), hemoglobin A1c levels (7.81±1.39-5.44±0.81%) and insulin doses (32.50±9.99-17.50±12.09 U/day, P<0.05). Out of 12 subjects receiving camel milk, insulin requirement in 3 subjects reduced to zero. There was nonsignificant change in plasma insulin and anti-insulin antibodies in both the groups. It may be stated that camel milk is safe and efficacious in improving long-term glycemic control, with a significant reduction in the doses of insulin in type 1 diabetic patients.
Article
Disulfide bonding of cysteines is one of the most important protein modifications, and it plays a key role in establishing/maintaining protein structures in biologically active forms. Therefore, the determination of disulfide bond arrangement is one important aspect to understanding the chemical structure of a protein and defining its functional domains. Herein, aiming to understand how the HIV-1 envelope protein's structure influences its immunogenicity, we used an MS-based approach, liquid chromatography electrospray ionization Fourier transform ion cyclotron resonance (LC/ESI-FTICR) mass spectrometry, to determine the disulfide linkages on an oligomeric form of the group M consensus HIV-1 envelope protein (Env), CON-S gp140 ΔCFI. This protein has marked improvement in its immunogenicity compared to monomeric gp120 and wild-type forms of gp140 Envs. Our results demonstrate that the disulfide connectivity in the N-terminal region of CON-S gp140 ΔCFI is different from the disulfide bonding previously reported in the monomeric form of gp120 HIV-1 Env. Additionally, heterogeneity of the disulfide bonding was detected in this region. These data suggest that the V1/V2 region does not have a single, conserved disulfide bonding pattern and that variability could impact immunogenicity of expressed Envs.
Article
The deposition behavior of milk and dairy protein model systems under turbulent flow conditions (Re > 66,700) was observed in the heating sections of a tubular ultra-high temperature processing unit. This phenomenon was monitored via thermal resistance of the deposit in four segments in each of two shell-and-tube heat exchangers. Model systems were comprised of mixtures of sodium caseinate, whey proteins, salts, lactose, and fat. Fouling rates varied with type of milk protein, heater wall temperature, and location in the heat exchangers. The relationship between deposition rate in the heat exchanger and protein denaturation kinetics was also examined.
Article
The denaturation and aggregation of reagent-grade (Sigmaalpha-La), ion-exchange chromatography purified (IEXalpha-La), and a commercial-grade (Calpha-La) alpha-lactalbumin were studied with differential scanning calorimetry (DSC), polyacrylamide gel electrophoresis, and turbidity measurement. All three preparations had similar thermal denaturation temperatures with an average of 63.7 degrees C. Heating pure preparations of alpha-lactalbumin produced three non-native monomer species and three distinct dimer species. This phenomenon was not observed in Calpha-La. Turbidity development at 95 degrees C (tau95 degrees C) indicated that pure preparations rapidly aggregate at pH 7.0, and evidence suggests that hydrophobic interactions drove this phenomenon. The Calpha-La required 4 times the phosphate or excess Ca2+ concentrations to develop a similar tau95 degrees C to the pure preparations and displayed a complex pH-dependent tau95 degrees C behavior. Turbidity development dramatically decreased when the heating temperature was below 95 degrees C. A mechanism is provided, and the interrelationship between specific electrostatic interactions and hydrophobic attraction, in relation to the formation of disulfide-bonded products, is discussed.
Article
Microfiltration and ultrafiltration were used to manufacture skim milks with an increased or reduced concentration of whey proteins, while keeping the casein and milk salts concentrations constant. The skim milks were heated on a pilot-scale UHT plant at 80, 90 and 120 degrees C. The heat-induced denaturation and aggregation of beta-lactoglobulin (beta-lg), alpha-lactalbumin (alpha-la) and bovine serum albumin (BSA) were quantified by polyacrylamide gel electrophoresis. Apparent rate constants and reaction orders were calculated for beta-lg, alpha-la and BSA denaturation. Rates of beta-lg, alpha-la and BSA denaturation increased with increasing whey protein concentration. The rate of alpha-la and BSA denaturation was affected to a greater extent than beta-lg by the change in whey protein concentration. After heating at 120 degrees C for 160 s, the concentration of beta-lg and alpha-la associated with the casein micelles increased as the initial concentration of whey proteins increased.