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Influence of alkalization treatment on the color quality and the total phenolic and anthocyanin contents in cocoa powder

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The effects of alkalization treatments on color, colorimetric fractions, total polyphenol content, and anthocyanin content of cocoa powder were investigated. A darker color and a lower total polyphenol content were obtained for cocoa powder alkalized using a K2CO3 solution than with an NaOH solution. A high temperature and basic pH conditions favored formation of dark components during alkalization due to sugar degradation, Maillard reactions, and anthocyanin polymerizing. The anthocyanin content decreased with an increasing alkali concentration, suggesting that more anthocyanins were transformed into brown polymers in darker cocoa powder. Cocoa powder with a heavy degree of alkalization had the lowest ratio of monomer anthocyanins to yellow/brown polymer content. OD460/OD525 values for alkalized samples were higher than for non-alkalized samples. Cocoa powder presented a better color quality after alkalization treatment.
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Food Sci. Biotechnol. 23(1): 59-63 (2014)
DOI 10.1007/s10068-014-0008-5
Influence of Alkalization Treatment on the Color Quality and the
Total Phenolic and Anthocyanin Contents in Cocoa Powder
Yue Li, Song Zhu, Yun Feng, Feifei Xu, Jianguo Ma, and Fang Zhong
Received: 22 May 2013 / Revised: 31 July 2013 / Accepted: 1 August 2013 / Published Online: 28 February 2014
© KoSFoST and Springer 2014
Abstract The effects of alkalization treatments on color,
colorimetric fractions, total polyphenol content, and
anthocyanin content of cocoa powder were investigated. A
darker color and a lower total polyphenol content were
obtained for cocoa powder alkalized using a K2CO3
solution than with an NaOH solution. A high temperature
and basic pH conditions favored formation of dark
components during alkalization due to sugar degradation,
Maillard reactions, and anthocyanin polymerizing. The
anthocyanin content decreased with an increasing alkali
concentration, suggesting that more anthocyanins were
transformed into brown polymers in darker cocoa powder.
Cocoa powder with a heavy degree of alkalization had the
lowest ratio of monomer anthocyanins to yellow/brown
polymer content. OD460/OD525 values for alkalized samples
were higher than for non-alkalized samples. Cocoa powder
presented a better color quality after alkalization treatment.
Keywords: cocoa, alkalization, color, polyphenol
Introduction
Cocoa powder is the primary raw material of chocolate,
and also an important flavor in food products, such as
baked goods, icings, and beverages (1). During processing,
cocoa powder is usually subject to alkalization treatments
for purposes of browning, wetability, dispersability, flavor,
and to enhance the nutritional and biological qualities of
cocoa (2-5).
In practice, cocoa to be alkalized is first heated in a
closed mixing vessel, followed by addition of a warm
alkali solution for a certain reaction time, and excess
moisture is then driven off by heating or drying. The end
products of the alkalizing process are cocoa solids with a
higher pH and a darker color than in the natural state (6).
Alkalization is one of several routes that may be used by a
manufacturer to modify the color of cocoa with different
susceptibilities to development of o-quinones and Maillard
reactions, especially non-enzymatic brown compounds (5).
The degree of alkalization is controlled by the strength of
the alkali solution, the alkali type, the length of the reaction
stage, and the process temperature (6).
Cocoa beans are rich in polyphenols, contributing 12-
18% of the dry weight of the whole bean. Cocoa polyphenols
have been associated with flavor, color, and the nutritional
value of cocoa products (7-10). Although polyphenols in
cocoa powder develop the specific color of cocoa products
through roasting and alkalization, few studies have focused
on the relationships among the alkalizing conditions, the
color of cocoa products, and the polyphenol content.
Since alkalization treatments are commonly used in the
processing of cocoa powder, the properties of cocoa powder
(colors and polyphenol content) can be controlled using
various alkalization parameters in order to meet the demands
of customers. This study was performed to determine the
alkalization effects. Cocoa powder was treated under different
degrees of alkalization and the effect of alkali types on
color and the polyphenol content of cocoa powder was
evaluated. Influences of alkalizing conditions on color,
colorimetric fractions, and the anthocyanin content of
cocoa powder were also investigated.
Yue Li, Yun Feng, Feifei Xu, Jianguo Ma, Fang Zhong ()
Key Laboratory of Food Colloids and Biotechnology, Ministry of
Education, School of Food Science and Technology, Jiangnan University,
Wuxi 214122, China
Tel: +86-13812536912; Fax: +86-510-85197876
E-mail: fzhong@jiangnan.edu.cn
Song Zhu
State Key Laboratory of Food Science and Technology, Jiangnan
University, Wuxi 214122, China
RESEARCH ARTICLE
60 Li et al.
Materials and Methods
Material Commercial cocoa powder without alkalization
was provided by Xing Guang Cocoa Product Limited
Company (Shaoxing, China). The fat content of the cocoa
powder was approximately 10%. Sodium hydroxide,
sodium carbonate, acetone, glacial acetic acid, gallic acid,
hydrochloric acid, methanol, formic acid, and other
analytical reagents were purchased from Sinopharm Group
Chemical Reagent Co., Ltd. (Shanghai, China) and were of
analytical grade.
Alkalization of cocoa powder Initially, cocoa powder
was alkalized using either sodium hydroxide (NaOH, 2%,
w/w) or potassium carbonate (K2CO3 2%, w/w) solutions
at a pressure of 0.06 MPa for 20 min. In order to identify
the influence of alkalizing conditions on coloration of
cocoa powder, alkalization was then carried out using an
NaOH solution under pressures of 0.02, 0.04, 0.06, 0.08,
and 0.1 MPa, NaOH solution concentrations of 1, 1.5, 2,
2.5, and 3%(w/w), and alkalization times of 10, 15, 20, 25,
and 30 min.
Color measurement The color of alkalized cocoa powder
was determined using a Hunter Tristimulus Colorimeter
(UltraScan XE; HunterLab, Reston, VA, USA) based on
L*, a*, and b* values. An amount of 10 g of cocoa powder
was used. The L* value represents the lightness component
on the surface and ranges from 0 to 100 (100 =light to
0= black). The a* and b* values are chromatic components
of redness to greenness and blueness to yellowness,
respectively (11,12). Data are reported as the mean value
from measurements of 8 different samples.
Total polyphenol analysis The total polyphenol content
was determined using the Folin-Ciocalteu procedure (13)
with some modification according to Elwers et al. (14).
Defatted cocoa powder (0.5 g) was extracted 3 times using
70% acetone (v/v) under constant agitation. After each
extraction, the sample was centrifuged (5424; Eppendorf,
Hamburg, Germany) at 8,000×g for 10 min. The three
supernatants were combined in a flask, and acetone was
removed using rotary evaporation (N-1001S-WA; Tokyo
Rikakikai Co., Ltd., Tokyo, Japan) under a partial vacuum
at 40oC. The residue was transferred to a volumetric flask
containing 2 mL of glacial acetic acid and diluted to 10 mL
with Milli-Q Plus water. The crude extract was diluted 1/
10 (v/v) with 2.5% aqueous acetic acid.
The extract or standard (0.5 mL), 0.5 mL of Folin-
Ciocalteu reagent, and 1.5 mL of Na2CO3 solution (20%,
w/v) were mixed and diluted to 10 mL with Milli-Q Plus
water in a volumetric flask and allowed to stand for 60 min
at room temperature. Absorption was measured at 760 nm
using a 722 spectrophotometer (Shanghai Precision &
Scientific Instrument Co., Ltd., Shanghai, China). Gallic
acid was used as a standard and the total polyphenol
content was expressed as gallic acid equivalents in mg/g.
All samples were analyzed in triplicate.
Color and colorimetric fractions determination Color
components were extracted (45 min shaking) using 50 mL
of 12 M HCl/CH3OH (1 mL/L) from 2 g of cocoa powder.
Extracts were filtered through Whatman 541 paper (GE
Healthcare, Pittsburgh, PA, USA). An aliquot of filtrate (4
mL) was adjusted to 25 mL using 12 M HCl/CH3OH. The
absorbance was read at 460 and 525 nm (15,16) in a 722
spectrophotometer (Shanghai Precision, Shanghai, China).
The rest of the filtrate was then applied to a column
(300 mm×15 mm i.d.; Shanghai Huxi, Shanghai, China)
containing 1.5 g of a previously conditioned absorbent
mixture of Silica G, Silicagel 60, and Polyclar AT (2/14/4).
Fractions of monomer anthocyanins (F1), red polymers
(F2), and yellow/brown polymers (F3) were eluted using
12 M HCl/CH3OH (1 mL/L), 50% formic acid, and pure
formic acid, respectively (25 mL of each solvent). The
absorbance was measured at 525 nm (16) using a 722
spectrophotometer (722; Shanghai Precision & Scientific
Instrument Co., Ltd.). Measurements were made in triplicate.
Statistical analysis Mean values were calculated and
Duncan’s t-test was performed using SPSS version 13.0 for
Windows software (SPSS Institute Inc., Cary, NC, USA).
Results and Discussion
Influence of alkali type on the color and polyphenol
content of cocoa powder Several alkali solutions can be
used for alkalizing process. NaOH and K2CO3 are the most
commonly used alkalis for cocoa powder alkalization
(6,17,18). The influence of NaOH and K2CO3 solutions on
the color (E) of cocoa powder is shown in Fig. 1. The
L* a* b* color system can provide uniformity in color
measurement and human perception (19,20), and is useful
for expression of visual color changes during browning.
An equation for calculating the color difference (E)
before and after alkalization was developed by Scofield
(21) as: E=((L)2+(a)2+(b)2)1/2. A higher E value
reflects the darker color of cocoa after alkalization. The
human eye is capable of noticing small differences
between colors on the order of 0.2 E (21). Cocoa powder
exhibited darker colors when a K2CO3 solution was used
for alkalization (Fig. 1). Since the two types of alkali used
have different basic strengths, Maillard reactions were
subject to different pH environments. Furthermore, Na+
and K+ ions may impact changes in anthocyanin structures
and, thus, produce different colors. It was reported that a
Alkalization Effects on Color of Cocoa Powder 61
K2CO3 solution generates a red-brown color and a
chocolate flavor in cocoa, and a NaOH solution has the
strong neutralization value of permitted alkalis, and it can
also produce red tones in press cake alkalization when
combined with an oxidation stage (17).
Polyphenols in cocoa powder are associated with human
health benefits and are involved in producing the typical
brown cocoa color and the astringent taste. The polyphenol
content was determined in cocoa powder after alkalization.
At the same concentration, alkalization with a NaOH
solution produced a higher polyphenol content than with a
K2CO3 solution (Fig. 1). Cocoa with a darker color had a
lower polyphenol content. To establish the relationship
between the color of cocoa powder and the total polyphenol
content, cocoa powder was treated with NaOH solutions
under various concentrations, reaction times, and pressures.
The relationship between the color of cocoa and the total
polyphenol content is shown in Fig. 2. The values of E,
L, a, and b were negatively correlated with the total
polyphenol content, indicating that a darker color is
associated with a lower total polyphenol content. During
the alkalizing procedure, polyphenols such as anthocyanins,
procyanidins, and catechins, are changed into quinones,
which suffer polymerization or form high molecular weight
insoluble brown compounds via protein linking (22). Thus,
the less astringent taste, the darker the cocoa powder with
a decreased polyphenol content.
Influence of alkalizing conditions on coloration of cocoa
powder Cocoa powder presented different colors under
varying degrees of alkalization using a NaOH solution
(Fig. 3). With an increase in pressure, alkali concentration,
or reaction time, the color of cocoa powder became darker.
The color compounds are polymers formed in the production
process as a result of sugar degradation and reactions
between amino compounds and carbohydrates (23). These
reactions were affected by changes in both pH and
temperature. A high temperature and basic pH conditions
favored formation of dark components in cocoa powder. It
was reported that Maillard reactions under acidic or basic
conditions produce a set of reaction products, including
non-volatile colored compounds of intermediate molecular
weight, and brown substances of high molecular weight
(23).
Influence of the alkali concentration on anthocyanins
Pigment is one of the most important factors for the color
of cocoa powder. In addition to Maillard reactions, dark
colors can also be produced by a combination of anthocyanin
and sugar, and the stability of cocoa powder increases via
glycosylation. Anthocyanin absorbance at 525 nm was
detected (Fig. 4). The absorbance value at 525 nm decreased
and the E value increased with an increasing alkali
concentration, suggesting that darker cocoa powder contains
less anthocyanin. The anthocyanin group of pigments
contains phenolic hydroxyl, and the D-heterocyclic oxygen
atom is quadrivalent. Thus, the pH values greatly impact
Fig. 3. Color of cocoa powder (L, a, b, and E) afte
r
v
arying conditions of alkalization. A light degree of alkalizatio
n
was carried out at a pressure of 0.02 MPa with a 1% NaOH
solution and an alkalization time of 20 min. A heavy degree o
f
alkalization was carried out at a pressure of 0.1 MPa with a 3%
N
aOH solution and an alkalization time of 30 min.
Fig. 1. Influence of the alkali type (NaOH and K2CO3) on the
color difference (E) and total polyphenol content of cocoa
powder.
Fig. 2. Relationship between the color of cocoa (L, a, b,
and E) and the total polyphenol content.
62 Li et al.
the anthocyanin structure. At different pH values, anthocyanin
has different configurations, resulting in different colors of
cocoa powder under different alkali concentrations during
alkalization. Additionally, hydroxy-furan carboxaaldehyde
may combine with anthocyanin and generate brown
pigment, resulting in a higher E value.
Influence of alkalizing conditions on colorimetric
fractions Brown pigments (products of anthocyanin
conversion) were analyzed at 460 nm and 525 nm using
spectrophotometer (722; Shanghai Precision & Scientific
Instrument Co., Ltd.). Cocoa powders at different degrees
of alkalization contained different anthocyanin contents
(Table 1). The OD460/OD525 values for alkalized samples
were higher than for non-alkalized samples (Table 1).
Previous study showed that the value of OD460/OD525 for a
good quality cocoa after fermentation and roasting should
not be less than 1.1 (16,24). The OD525 and OD460 absorbance
values for all the alkalized samples were lower than for
non-alkalized counterparts, probably due to anthocyanin
polymerization.
Other indicators of cocoa quality based on color were
the monomer anthocyanin content (F1), the red polymer
content (F2), and the yellow and brown polymer content
(F3). These fractions were separated using column
chromatography (Shanghai Huxi). The ratio of F1 to F3
(F1/F3) indicates changes in pigment concentrations.
According to Serra and Ventura (3), the F1/F3 value should
not exceed 0.33 for good quality cocoa. The value of F1/
F3 for cocoa powder with a heavy degree of alkalization
was lowest, indicating that more anthocyanins were
polymerized into red polymers (Table 1). All alkalized
samples had lower F1/F3 values than cocoa powder
without alkalization, suggesting that more anthocyanins
were transformed into brown polymers, compared to non-
alkalized samples. Anthocyanins are probably hydrolyzed
and the resultant aglycones are oxidized to quinonic
compounds, contributing to the typical brown color of
cocoa powder (3,25).
Alkalization is commonly used in the processing of
cocoa powder, and the color qualities of cocoa powder can
be improved by optimizing alkalization parameters. Cocoa
powder alkalized under different conditions and degrees of
alkalization was studied for color, polyphenol content,
color fractions, and qualities. Cocoa powder alkalized with
a 2%(w/w) K2CO3 solution exhibited a darker color and
had a lower polyphenol content than powder alkalized with
a NaOH solution. Cocoa powder was observed to be darker
when the total polyphenol content was reduced. The
reaction was faster at a higher temperature and a basic pH,
resulting in a darker cocoa powder color (8,23). More
anthocyanins were transformed into brown polymers when
the alkali concentration was increased during alkalization.
Alkalized cocoa powder had a better color quality and was
less astringent, compared to non-alkalized powder.
Acknowledgments This work was financially supported
by National 125 Program 2011BAD23B02, 2013AA1022207;
SFC 31171686; NSF-Jiangsu-BK2012559; PAPD, China.
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In the contemporary context, climatic conditions in cocoa bean-producing countries and disrupted logistics chains due to the coronavirus pandemic complicate stable cocoa products supply. The study aimed at developing an express assessment method for color characteristics of cocoa-containing food systems where cocoa powder replaced with brown pigment melanin obtained from buckwheat husks, partially. A man prepared five confectionery glaze prototypes: one based on non-alkalized cocoa powder and four samples containing 3; 5; 7 and 10 % melanin powder as a substitute for cocoa powder. The confectionery glaze based on alkalized cocoa powder served as a comparison sample. To study the glaze color characteristics, the researchers covered white plates with samples, enabled the glaze to harden, and then, took images of the glaze surface using a digital camera in a white box at a color temperature of 6000 K; processed images using image analysis software that provided color coordinates determination of any point of the uploaded image in the RGB model. Then, a man determined the color coordinates in trichromatic XYZ coordinates using a color converter. The results revealed that the confectionery glaze prototype containing 15% non-alkalized cocoa powder and 10% melanin was close to the control sample in terms of color characteristics. The suggested approach advantages are the expensive equipment absence, simplicity and data processing accessibility. The method enables running an objective color assessment of a cocoa-containing product, comparing product samples with each other, and defining color differences. The research results offer the challenges for the color scales development for cocoa-containing foods quality assessment.
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The volatile flavor compounds are the most important indicators of the quality of cocoa beans, among which pyrazines are considered as the main and key groups affecting the cocoa flavor. In cocoa processing, roasting is an important stage in the technical treatment of cocoa and has a significant impact on chemical properties of cocoa and its flavor. The present study aimed to assess the impact of roasting (temperature and time) on alkyl pyrazines, as key flavor compounds, via gas chromatography–mass spectrometry. Additionally, other properties, including color, polyphenols, chemical properties, and sensory attributes of cocoa powder were investigated. The results indicated that with the change in roasting time and temperature, these properties changed significantly. The cocoa powder roasted at 140 °C for 40 min had the highest browning index value (OD460/OD525), tetramethylpyrazine to trimethylpyrazine (TMP/TrMP) ratio, and sensory evaluation score and the lowest polyphenol content compared to the other samples.
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This work is focused on the study of the metabolomic changes that occur in cocoa powder throughout the alkalization process by using an untargeted ultra high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-QTOF-MS) metabolomics approach. With this aim, cocoa powder samples submitted to different alkalization degrees (light, medium, and strong) were analyzed. Metabolite extraction was performed using 75% MeOH in water since it provided the highest number of molecular features. After data processing, non-supervised and supervised methods were applied to carry out the statistical data analysis. Thus, the most significant metabolites that allow establishing differences among the cocoa powder samples submitted to the alkalization processes were pointed out. Thus, 43 and 30 metabolites in positive and negative ionization modes, respectively, demonstrated to be relevant. Among them, 9 compounds were unequivocally identified and 22 tentatively identified. Most of them were amino acids, alkaloids, organic acids or polyphenols, among others.
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In this work, the structure of the haze of the blackberry wine and its main polyphenol components was evaluated. The shape of the haze of blackberry wine was observed by scanning electron microscope (SEM) and atomic force microscope (AFM), which revealed the leaf like particles with a thickness of about 2 nm. The formation of haze was associated with the accumulation of these smaller particles (rather than crystallization) to form larger particles which were preferentially precipitated to the bottom of the bottle during the aging of red wine. The main components of the haze of the blackberry wine were identified by high performance liquid chromatography (HPLC), solid state nuclear magnetic resonance (SS-NMR), Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The results showed that polyphenols and protein with proportions of 37.48 g/100 g and 18.22 g/100 g, respectively. They are predominant in the blackberry wine haze, followed by 5.10 g/100 g total sugar and 17.99 g/100 g water. Ellagic acid (EA) and sanguisorbic acid (SA), as the main polyphenols, combined with protein to form haze. Among the trace elements in haze, the contents of sulfur, phosphorus and iron were higher with proportion of 0.61 g/100 g, 0.14 g/100 g and 0.14 g/100 g, respectively. This is the first time to report the haze structure of blackberry wine and the main polyphenol compounds in haze. This work provides a reference for research on formation mechanism of the haze of fruit wine and reducing or solving of them.
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Recently, polyphenols have gained much more attention, owing to their antioxidant capacity (free radical scavenging and metal chelating) and their possible beneficial implications in human health, such as in the treatment and prevention of cancer, cardiovascular disease, and other pathologies. Cocoa is rich in polyphenols particularly in catechins (flavan-3-ols) and procyanidins. Polyphenol contents of cocoa products such as dark chocolate, milk chocolate and cocoa powder have been published only recently. However, the data vary remarkably due to the quantity of cocoa liquor used in the recipe of the cocoa products but also due to the analytical procedure employed. For example, results obtained by a colourimetric method were 5–7 times higher for the same type of product than results obtained by high performance liquid chromatography (HPLC). In 1994, the per head consumption of chocolate and chocolate confectionery in the European Union ranged from 1.3 kg/year in Portugal to 8.8 kg/year in Germany. In general, consumers in the Northern countries consume on average more than people in the South. Thus, chocolate can be seen as a relevant source for phenolic antioxidants for some European population. However, this alone does not imply, that chocolate could be beneficial to human health. Some epidemiological evidence suggests a beneficial effect to human health by following a polyphenol-rich diet, namely rich in fruits and vegetables and to a less obvious extent an intake of tea and wine having a similar polyphenol composition as cocoa. In many experiments cellular targets have been identified and molecular mechanisms of disease prevention proposed, in particular for the prevention of cancer and cardiovascular diseases as well as for alleviating the response to inflammation reactions. However, it has to be demonstrated, whether polyphenols exert these effects in vivo. One pre-requisite is that the polyphenols are absorbed from the diet. For monomeric flavonoids such as the catechins, there is increasing evidence for their absorption. For complex phenols and tannins (procyanidins) these questions have to be addressed for the future. Some indication for the absorption of procyanidins derive from studies with the human colon cancer cell line Caco-2, believed to be a valuable model for passive intestinal absorption as proposed for polyphenols. However, it has to be clarified which concentration is effective and what concentrations can be expected from food intake. Another open question is related to polyphenol metabolism. For example, much effort has been invested to show antioxidative effects of free unbound polyphenols, especially of catechins and the flavonol quercetin. However, only a very small part can be found in plasma in the free form but conjugated or even metabolised to several phenolic acids and other ring scission products. From the papers reviewed, it is as yet to early to give an answer to the question, whether chocolate and/or other sources rich in catechins and procyanidins are beneficial to human health. Even though some data are promising and justify further research in the field, it has to be shown in future, whether the intake of these functional compounds and/or their sources is related to measurable effects on human health and/or the development of diseases.
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Rapid advances in our knowledge of the proanthocyanidins were made during the last decade, and although this review necessarily concentrates upon recent aspects, this is also an appropriate moment to look at the subject in a broader context. With this viewpoint in mind facets of earlier work which are of importance-such as the solvolytic reactions of flavan-3,4-diols-and related areas of research into natural phenolic compounds are discussed.
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A fully automated-continuous flow 40-sample/ hour procedure was adapted from the Singleton-Rossi method of analysis for total phenols in wine and other plant extracts. It was compared with small-volume manual and semiautomated versions of this analysis. The agreement in mg of gallic acid equivalent phenol (GAE) per liter among a series of dry wines was excellent by all three procedures. The coefficients of variation in replicate analyses averaged 5.8% for the manual, 6.2% for the semi-automated and 2.2% for the automated procedure. This greater reproducibility, plus savings of about 70% in labor and up to 40% in reagents, makes the automated procedure attractive for laboratories doing enough total phenol analyses to recoup the cost of the automating equipment. For continuous flow, color development with the Folin-Ciocalteu reagent in alkaline solution must be hastened by heating compared to slower room temperature development for the manual methods. Heating of sugar-containing samples in the alkaline solution gives interference presumably from endiol formation. Examples are given of corrections which were used successfully to estimate the true phenol content of sweet wines.
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The influence of temperature and water activity on color degradation in paprika powders was investigated. The Hunter color parameters (L, a, b), hue angle (h), and total color difference (TCD) were used to estimate the color changes of paprika during thermal treatment at different temperatures (60, 80 and 99°C) and water activities (0.459, 0.582 and 0.703). The changes in L, a, b and TCD values were significantly influenced by the processing time, temperature and water activity. The color changes during processing and storage were described by a first order kinetic model. The temperature dependence of the degradation followed the Arrhenius relation. Samples with a high water activity exhibited a high rate constant of the color degradation. The effect of water activity on activation energy was not significant. A linear relationship between the water activity and rate constant of the color parameters was found. By incorporating the linear relationship krefaw into the Arrhenius equation, a modified Arrhenius equation was proposed which was used to predict paprika color changes as influenced by temperature and water activity.
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The Ivory Coast cocoa beans were roasted in a convective oven at 110, 135 and 150°C, at the air flow rate of 1.0m/s and relative air humidity (RH) of 0.8–0.4%, 2.0% and 5.0%. Pigmentation expressed as both OD460/OD525 and a ratio of anthocyanins to yellow and brown pigments (F1/F3) and water content were assayed throughout cocoa roasting. The experiments provided evidence that higher humidity of air (particularly of 5.0%) was beneficial to the color of roasted cocoa beans. The beans roasted at 135 and 150°C displayed desired coloration (OD460/OD525 above 1.1, and F1/F3 below 0.33).
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Cocoa is a food ingredient that is important for the contribution of flavor to foods but is also associated with potential health benefits. The chemistry thought to be responsible for its cardiovascular health benefits is the flavanol (flavan-3-ol) antioxidants. Evidence from the literature indicates that natural cocoas are high in flavanols, but when the cocoa is processed with alkali, also known as Dutch processing or Dutching, the flavanols are substantially reduced. This paper provides a survey of the physical and chemical composition of representative natural cocoas and lightly, medium, and heavily alkalized cocoas. As part of the survey, both brown/black and red/brown alkali-processed cocoas were measured. Natural cocoa powders have an extractable pH of 5.3−5.8. Alkalized cocoa powders were grouped into lightly treated (pH 6.50−7.20), medium-treated (pH 7.21−7.60), and heavily treated (pH 7.61 and higher). The natural, nonalkalized powders had the highest ORAC and total polyphenols and flavanols (including procyanidins). These chemical measurements showed a linear decrease as the extractable pH of the cocoa powder increased. Likewise, the flavanol monomers, oligomers, and polymers all showed a linear decrease with increasing pH of the final cocoa powder. When brown/black cocoa powders were compared to red cocoa powders, similar decreases in flavanols were observed with increased alkalization. The average total flavanol contents were 34.6 ± 6.8 mg/g for the natural cocoas, 13.8 ± 7.3 mg/g for the lightly processed cocoas, 7.8 ± 4.0 mg/g for the medium processed cocoas, and 3.9 ± 1.8 mg/g for the heavily processed cocoa powders. The observed linear and predictable impact of alkalization on flavanol content is discussed with respect to other reports in the literature as well as what implications it may have on diet and food manufacturing.Keywords: Alkalization; Dutching; flavanols; flavan-3-ols; procyanidins; antioxidants; cocoa powder; cacao
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Polyphenols were analysed at 280 nm by HPLC device using a Photodiode Array Detector (PDA). Anthocyanins were separated with the SEP-PAK Vac 6cc 1000 mg (Waters) column and measured at 520 nm with a PDA. Nineteen cacao clones from Cameroon genebank were analysed. Fresh and fermented-like seeds were used. Two main polyphenols were present in our samples: catechin and epicatechin. Epicatechin represents 2–4% DM of defatted cocoa seed powder. Undefined substances called A, B and C were also found in cocoa seeds. Substance A is discussed as a derivative of caffeic acid and an ester-bound compound. Substances B and C are oligomeres of proanthocyanidins. Protocatechiuc acid and quercetin were not detected. Two anthocyanins were found in cocoa seeds: cyanidin-3-galactoside and cyanidin-3-arabinoside. They represent 0.02–0.4% DM of defatted cocoa seed powder. Total phenols, catechin, epicatechin and anthocyanin in fresh and fermented-like beans were genotype-dependent. Polyphenols from seeds of two different pods from the same clone showed a quantitative significant difference. Spearman's correlation test showed that there is no correlation between the number of seeds per pod, weight of pod and content of polyphenolic compounds. Nevertheless, a negative correlation was found between the number of seeds per pod and the catechin content (r ¼ À0:463; Po0:01). Groupings of samples were observed using PCA and hierarchical cluster analysis. The separation between groups is related to their polyphenol and anthocyanin contents.