Patrick Silcock

Patrick Silcock
University of Otago · Department of Food Science

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146
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Publications

Publications (146)
Article
Full-text available
In food technology, the term ‘fermentation’ encompasses a spectrum of microbial‐driven bioprocesses that preserve and improve the quality of raw materials, transforming them into new fermented products with minimal resource consumption. Furthermore, fermentation plays a crucial role in driving the eco‐friendly transformation of the agricultural ind...
Article
Full-text available
Bacterial fermentation is considered to be a cost-effective means of generating desired flavour compounds from plant-based substrates. However, the wide range of substrates present in plants makes it challenging to understand how individual components impact on flavour volatile organic compound (VOC) production. To simplify this, a defined medium c...
Article
Full-text available
Lactic acid bacteria (LAB) fermentation is a viable approach for producing plant-based flavour compounds; however, little is understood about the impact of different LAB strains and medium compositions on the production of volatile organic compounds (VOCs). This study investigated the impact of the addition of individual amino acids (AAs) (L-leucin...
Article
Full-text available
Fermentation by lactic acid bacteria (LAB) is a promising approach to meet the increasing demand for meat or dairy plant-based analogues with realistic flavours. However, a detailed understanding of the impact of the substrate, fermentation conditions, and bacterial strains on the volatile organic compounds (VOCs) produced during fermentation is la...
Article
Full-text available
The impact of the ethylene inhibitor, 1-methylcyclopropene (1-MCP), on four apple cultivars (Braeburn, Fuji, Jazz and Golden Delicious) over 150 days of storage at 2 °C was assessed. Proton transfer reaction quadrupole mass spectrometry (PTR-QUAD-MS) was used to monitor changes in VOC composition, while texture analysis and X-ray microcomputer tomo...
Article
Higher alcohols and esters are among the predominant classes of volatile organic compounds (VOCs) that influence the quality of beer. The concentrations of these compounds are determined through a specific yeast strain selection and fermentation conditions. The effect of yeast strains on the formation of higher alcohols and esters throughout fermen...
Article
Full-text available
The consumer rejection threshold (RjT) method was applied to determine the total microbial numbers (TMNs) where consumers find that the quality of whole fresh chilled pasteurised milk (WFCPM) and skim milk (Trim) stored at 4.5 ± 0.5 °C is no longer acceptable. Food spoilage progression was supported by measurements of VOCs and the terms consumers u...
Article
Full-text available
Butein, a rare chalcone found in the toxic plant Toxicodendron vernicifluum, has been shown to regulate glucose homeostasis via inhibition of the nuclear factor kappa-B kinase subunit beta (IKKβ)/nuclear factor kappa B (NF-κB) pathway in the brain. Here, we investigated whether the non-poisonous plant Dahlia pinnata could be a source of butein as a...
Article
Full-text available
Health, environmental and ethical concerns have resulted in a dramatic increase in demand for plant-based dairy analogues. While the volatile organic compounds (VOCs) responsible for the characteristic flavours of dairy-based products have been extensively studied, little is known about how to reproduce such flavours using only plant-based substrat...
Article
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Hop-derived volatile organic compounds (VOCs) and their transformation products significantly impact beer flavour and aroma. Geraniol, a key monoterpene alcohol in hops, has been reported to undergo yeast-modulated biotransformation into various terpenoids during fermentation, which impacts the citrus and floral aromas of the finished beer. This st...
Article
Full-text available
The perception of hop-derived flavour in beer is not well understood, particularly regarding the effect that different yeast strains and fermentation parameters have on perceived hop aroma and the mechanisms responsible for these changes. To evaluate the influence of yeast strain on the sensory properties and volatile composition of beer, a standar...
Article
Full-text available
Sound is a physical stimulus that has the potential to affect various growth parameters of microorganisms. However, the effects of audible sound on microbes reported in the literature are inconsistent. Most published studies involve transmitting sound from external speakers through air toward liquid cultures of the microorganisms. However, the dens...
Article
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To maximise tenderness, minimise cooking loss, and decrease the adverse effects on the colour of beef short ribs, third-order multiple regression models were used to optimise the processing parameters during the pulsed electric fields (PEF) followed by sous vide (SV) processing. Electric field strength (EFS) and specific energy (SE) of PEF ranged f...
Article
The aim of this research was to investigate how the electrical conductivity of short ribs affected Pulsed Electric Field (PEF) process parameters and the ability of PEF to enhance their quality and reduce sous vide processing time. Short ribs with different range of electrical conductivity (3-6, 6-9, and 9-12 mS/cm) values were treated using input...
Article
The impact of Pulsed Electric Field (PEF) processing pre-treatment on the texture and kinetics of in vitro starch digestibility of French fries made from two potato cultivars (Solanum tuberosum L.) containing dry matter content ranging from 19 to 22% was investigated. Whole and steam-peeled potato tubers were treated with a pilot scale PEF unit (el...
Article
Sourdough bread has a complex flavour profile, which is strongly influenced by the compounds generated during fermentation by the diverse array of microorganisms present, mainly yeasts and lactic acid bacteria (LAB). Twelve complex sourdough cultures, comprised of mixtures of yeast and bacteria, were propagated using wholemeal flour and used in the...
Article
Full-text available
This study investigated differences between general New Zealand consumers and ethnic Chinese consumers living in New Zealand regarding the importance of lamb attributes at the point of purchase and opinions of New Zealand lamb. A central location test survey was undertaken with 156 New Zealand consumers living in Dunedin, New Zealand, and 159 Chine...
Article
Full-text available
The aim of this research was to study the effect of sous vide temperature (60, 65, and 70 °C) and time (12, 24, and 36 h) combination on the quality of beef short ribs, namely colour, cooking loss (%), shrinkage (%), soluble collagen (%), myofibrillar fragmentation index (MFI), Warner–Bratzler shear force (WBSF), and Texture Profile Analysis (TPA)...
Article
Relationships between overall liking scores for cooked lamb from Chinese (n=158) and New Zealand (n=156) consumers, and metabolite and lipid profiles were evaluated. Consumers assessed meat from 6-8-month-old lambs of composite genetics fed chicory (CHIC) or grass (GRASS), and from 12 month–old Merino lambs fed a mixed pasture (PMER). On average, C...
Chapter
Proton transfer reaction-mass spectrometry (PTR-MS) is a quantitative analytical technique for the online detection of gas-phase volatile organic compounds (VOCs), among them aroma compounds, over a broad dynamic range and down to ultra-trace concentrations. Its rapid detection capabilities and high sensitivity make it an ideal tool in food science...
Preprint
Full-text available
The aim of this research was to study the effect of sous vide temperature (60, 65, and 70°C) and time (12, 24, and 36 h) combination on the quality of beef short ribs namely colour, cooking loss (%), shrinkage (%), soluble collagen (%), myfibrillar fragmentation index (MFI), Warner Bratlzler Shear force (WBSF), and Texture Profile Analysis (TPA) pa...
Chapter
Pulsed electric fields (PEF) technology is used in meat processing to increase cell membrane permeability or to form permanent pores in muscle cells. This cellular disintegration can increase the tenderness of low-value tough meat cuts, enhance mass transfer, and improve the efficiency and cost-effectiveness of subsequent unit operations such as so...
Article
Full-text available
This study investigated the impact of varying sound conditions (frequency and intensity) on yeast growth, fermentation performance and production of volatile organic compounds (VOCs) in beer. Fermentations were carried out in plastic bags suspended in large water-filled containers fitted with underwater speakers. Ferments were subjected to either 2...
Article
Full-text available
Based on unsteady state heat conduction, a mathematical model has been developed to describe the simultaneous heat and moisture transfer during potato frying. For the first time, the equation was solved using both enthalpy and Variable Space Network (VSN) methods, based on a moving interface defined by the boiling temperature of water in a potato d...
Article
Full-text available
Loin sections (m. Longissimus lumborum) were collected at slaughter from forty-eight lamb carcasses to evaluate consumer-liking scores of six types of typical New Zealand commercial lamb and to understand the possible underlying reasons for those ratings. A consumer panel (n = 160) evaluated tenderness, juiciness, flavor liking, and overall liking...
Article
Aims/hypothesesWe examined the effects of milling and cooking whole grains in water to achieve starch gelatinisation on postprandial blood glucose using a randomised crossover open-label design. Participants were adults with type 2 diabetes whose body weight or medications had not changed in at least 3 months.Methods Postprandial blood glucose (mea...
Article
Full-text available
Hop aroma characteristics originate from hop essential oils, which have complex chemical profiles that remain poorly understood, particularly for New Zealand hops. The aim of this study was to determine volatile compounds that distinguish New Zealand hop cultivars. Untargeted fingerprinting methods based on headspace gas chromatography mass spectro...
Article
Full-text available
Animal production factors can affect the fatty acid and volatile profile of lamb meat. The fatty acid and volatile composition of the M. longissimus thoracis was evaluated from 150 lambs from 10 groups of commercial lambs that differed in age, sex, diet and breed, from three farms, which represent typical forage lamb production systems in New Zeala...
Article
Glycerol monooleate (GMO), casein and whey proteins are surfactants that can stabilize emulsion systems. This study investigates the impact of instantized GMO powders on creaming stability and oxidative stability in protein-stabilized emulsions. Model emulsions with bulk GMO, two instantized GMO powders, and two controls (without GMO) were produced...
Article
Full-text available
Deep-fried foods (e.g., French fries, potato/veggie crisps) are popular among consumers. Recently, there has been an increased interest in the application of Pulsed Electric Fields (PEF) technology as a pretreatment of plant-based foods prior to deep-frying to improve quality (e.g., lower browning tendency and oil uptake) and reduce production cost...
Article
Bacillus cereus spores pose a challenge to the food industry owing to their ability to germinate in food during storage and produce toxins. The objective of the current study was to investigate the effect of pulsed electric field (PEF) at low electric field strength (i.e., 7.3, 8.1, 8.8 and 9.4 kV/cm) and moderate temperatures (65, 70, 75 and 80°C)...
Article
Full-text available
This study aimed to elucidate changes in volatile, phenolic, and oenological profiles of wines vinified from Pulsed Electric Fields (PEF)-treated and untreated Merlot grapes during bottle storage of up to 150, 90, and 56 days at 4 °C, 25 °C, and 45 °C, respectively, through chemometrics technique. Wines produced from untreated grapes and those PEF-...
Article
Glycerol monooleate (GMO) improves creaming stability in protein-stabilised emulsions but is unsuitable for direct aqueous applications due to its low solubility in water. Encapsulation could transform waxy solid GMO into a water-dispersible powder. This study assessed spray-drying to produce instantised GMO powders, and investigated emulsion formu...
Article
The conditions used to generate wood smoke for the purpose of smoking food greatly affect the flavor character of the resulting food. The relationships between wood type and smoke generation conditions and the resulting volatile composition and flavor character are not well understood. The objective of this study was to characterize the volatile or...
Article
Carcass attributes and meat quality characteristics of the Longissimus thoracis muscle were evaluated from 135 lambs from 9 commercial forage production systems (n = 15) on 3 farms. Wethers had greater eye muscle area and loin intramuscular fat percentage than cryptorchid lambs (P < 0.05). Chicory-fed lambs had a heavier carcass weight and greater...
Article
Objective: Wholegrain foods vary in the extent of processing. We investigated whether wholegrain particle size in bread influences postprandial glycemia in type 2 diabetes. Research design and methods: Postprandial glycemia (incremental area under the blood glucose curve [iAUC]) was measured after consumption of three breads made with roller-mil...
Article
Full-text available
Methionine and riboflavin have been identified as key reactants in the development of off‐flavours induced by light exposure. However, the mechanism behind the production of volatiles organic compounds (VOCs) that are generated during the early stages of light exposure is still unclear. To provide new insights into the development of light‐induced...
Article
This study assessed the feasibility of using a multiplatform approach; integrating untargeted fingerprinting of volatiles and targeted profiling of phenolic and oenological attributes (soluble solids, pH, titratable acidity and colour properties) coupled with chemometrics to understand complex (bio) chemical reactions occurring during Merlot red wi...
Article
Merlot grapes have high proportion of anthocyanins protected inside cell vacuoles but the thick skins limit their extractability. This study investigated the effect of a continuous Pulsed Electric Fields (PEF at 500 kg/h) system operated at high-intensity electric field strengths (>30 kV/cm) combined with energy inputs ranging from 4.7 to 49.4 kJ/L...
Article
Probiotics are defined as live microorganisms, which, when administered in adequate amounts, confer health benefits to the host. Traditionally, probiotic food research has heavily focused on the genera Bifidobacteria and Lactobacilli, along with their benefits for gut health. Recently with the identification of new probiotic strains specifically in...
Article
This study investigated the changes in physicochemical properties and volatile compounds of beef bone hydrolysates during heat treatment as a result of the Maillard reaction (MR). Five beef bone hydrolysates obtained from single (P-Protamex®, B-bromelain, and F-Flavourzyme®) and simultaneous (P + F and B + F) enzymatic hydrolysis treatments were co...
Conference Paper
Full-text available
Comparisons were made of carcass and meat quality characteristics of three groups of wether lambs (n=15/group): a composite breed slaughtered at weaning (EARLY), and at 6-8 months of age (MID) and Merino lambs slaughtered at 12 months of age (LATE). Carcass weight and eye muscle area were measured and meat quality was measured on the Longissimus th...
Article
Full-text available
Egg proteins can be used in a wide range of food products, owing to their excellent foaming, emulsifying, and gelling properties. Another important functional property is the susceptibility of egg proteins to enzymatic hydrolysis, as protein digestion is closely related to its nutritional value. These functional properties of egg proteins are likel...
Article
Red meats such as pork contain pro-oxidative heme proteins that can act as initiators of protein oxidation. The present study investigated the interrelationships between different forms of myoglobin, lipid oxidation and protein carbonyls in minced pork packaged under modified atmosphere (30% CO 2 and 70% O 2) and stored at 4 °C for 12 days. Peroxid...
Article
Full-text available
The effect of pulsed electric fields (0.7 and 1.5 kV/cm, specific energy 90–100 kJ/kg) processing followed by post–pulsed electric field (PEF) ageing ( 0, 3, 7, 14 days) on the safety and quality attributes of sous vide–processed (60 °C/12 or 24 h) beef briskets was assessed. Ageing did not significantly reduce the hardness of sous vide–processed m...
Article
Wine is an extremely complex beverage that contains a multitude of volatile and nonvolatile compounds. This study investiged the effect of vineyard site and grapevine clone on the volatile profiles of commercially produced Pinot noir wines from central Otago, New Zealand. Volatile metabolites in Pinot noir wines produced from five grapevine clones...
Conference Paper
Full-text available
Methionine and riboflavin are key reactants in the development of light-induced off-flavors. However, the formation of these volatiles during the early stages of light exposure is still unclear. To provide new insights into the light-induced oxidation of milk, methionine and riboflavin model solutions were exposed to fluorescent light for up to 6 h...
Article
Differential gene expression was used to explore the mechanisms underpinning the differences in the impact of heat activation (70 °C for 30 min) on the germination of Bacillus cereus spores in the presence and absence of a germinant (L-alanine). The number of germinated cells, after heat activation plus L-alanine (3.5 ± 0.02 log CFU/ml) in the spor...
Article
Full-text available
This study used multiple regression to model the effect of pulsed electric field (electric field strengths 0.7, 1.0 or 1.5 kV cm⁻¹) and sous vide (60 °C for either 12, 18 or 24 h) processing on the quality parameters (tenderness, cooking loss, colour, lipid stability) of beef brisket. Pulsed electric fields (PEF) at 0.7 kV cm⁻¹ and 1.5 kV cm⁻¹ foll...
Article
Full-text available
The goal of this research was to optimise sous vide processing parameters for beef briskets, previously treated with pulsed electric fields (PEF), to enhance meat tenderness while maintaining other quality attributes such as water holding capacity, colour, and collagen solubility. PEF-treated briskets (electric field strength 1.5 kV/cm; specific en...
Article
This research investigated the effects of pulsed electric fields (PEF) (1.4–1.7 kV/cm, 653–695 kJ/kg) and heating (60 and 80 °C for 10 min) at different pH (4, 5, 7, and 9) on the antioxidant and anti-inflammatory activity of ovomucin-depleted egg white (OdEW) after in vitro gastrointestinal hydrolysis. PEF and heating (80 °C for 10 min) at pH 4 en...
Article
Volatile organic compounds (VOCs) released from fresh meat during storage have the potential to be reliable parameters for monitoring shelf-life and/or spoilage using simple sensors. The VOC release profiles in raw, minced pork packaged under modified atmosphere (70% O2, 30% CO2) stored at 4 °C were measured on days 0, 3, 6, and 12 of storage by pr...
Article
Bacillus cereus spores in food are able to survive pasteurization, and if conditions are favourable, subsequently germinate, grow and produce toxins causing food poisoning. The objectives of this study were to firstly determine the impact of cold storage and ion uptake on the thermal resistance of B. cereus spores and secondly to use differential g...
Article
Hop-derived volatile organic compounds (VOCs) play an important role in the flavor and aroma of beer, despite making up a small percentage of the overall profile. To understand the changes happening during fermentation, proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) was applied for the first time in brewing science to direct...
Article
The impact of different ratios of lean meat, adipose tissue (fat) and bone on the volatile organic compound (VOC) profile of vacuum-packed (VP) lamb stored at 2 °C for up to 15 days was investigated using two sampling approaches. VOC development in individual samples was followed over time using either a traditional sampling regime where replicate...
Article
B. cereus spores are a concern to the food industry, especially to the producers of heat sensitive food products like egg white or precooked and stored food such as fried rice. This study investigated the impact of nutrients, temperature (4, 8, 15 and 25 °C), pH (4, 5, 7 and 9), and cold storage on the germination, growth and resistance of B. cereu...
Article
Protein susceptibility to in vitro gastrointestinal digestion of ovomucin-depleted egg white (OdEW) adjusted to pH 4, 5, 7 and 9 and processed by heat (60 and 80 °C for 10 min) or pulsed electric fields (PEF) (1.4–1.8 kV/cm, 259–695 kJ/kg) was studied by assessing peptide production, proteolytic pattern, and the final peptide profile. Ovotransferri...
Article
Total microbial numbers (TMN*) is a widely used, yet broad indicator of the quality of fresh chilled pasteurized milk (FCPM). Changes in the sensory characteristics (trained panel, n = 9), volatile organic compounds (VOC) composition (proton transfer reaction mass spectrometry, PTR-MS), and TMN were assessed for FCPM stored at 4.5 °C ± 0.5 for up t...
Article
The applicability of using front-face fluorescence spectroscopy to compare profiles of commercially produced New Zealand Pinot Noir grape juice and wine samples from closely related vineyard sites and different grapevine clones was assessed by monitoring eleven batches of grape juices (different sites and clones) during the commercial winemaking pr...
Article
The volatile organic compound profile in beer is derived from hops, malt, yeast, and interactions between the ingredients, making it very diverse and complex. Due to the range and diversity of the volatile organic compounds present, the choice of the extraction method is extremely important for optimal sensitivity and selectivity. This study compar...
Article
Characteristic attributes of pea-protein fortified, extruded rice snacks were evaluated by mechanical, acoustic and descriptive sensory analysis. The addition of pea protein isolate (0 to 45% (w/w)) to rice flour and extruder screw speed strongly affected the expansion behaviour and therefore, textural attributes of extruded snack products. The sen...
Article
Full-text available
The creation of axillary body odor and its interaction with worn textiles is of continuing interest to textile manufacturers and finishers, product developers and marketers, and end users. This paper explains a novel proton transfer reaction – mass spectrometry model system to investigate the adsorption and release behavior of three fiber types com...
Article
Brisket is a low value/tough meat cut that contains a large amount of connective tissue. Conversion of collagen into gelatin during heating reduces the toughness of the connective tissue however this conversion is slow at low cooking temperatures (around 60. °C). The objective of this project was to determine the ability of pulsed electric field (P...
Article
The addition of proteins to extrusion feed formulations can strongly affect the expansion behaviour of the melt and often results in limited expansion of the final product. Therefore, the aim of this study was to investigate the impact of pea protein isolate (PPI) content (0-30%) and extruder screw speed (300-700 rpm) on the (i) initial and final e...
Article
Egg proteins have various functional and biological activities which make them potential precursor proteins for bioactive peptide production. Simulated in vitro gastrointestinal digestion and enzymatic hydrolysis using non-gastrointestinal proteases have been used as tools to produce these peptides. Bioactive peptides derived from egg proteins are...
Article
This study investigated the effect of vineyard site on the volatile profiles of Pinot Noir wines using proton-transfer reaction mass spectrometry with prior headspace dilution. The ANOVA and PCA enabled discrimination of wine based on vineyard site. Sample separation was due to differences in the ratios of a mixture of compounds, including higher a...
Article
The physical and structural properties of pea-protein-fortified, expanded snacks were examined after extrusion at various moisture contents, temperatures, screw speeds and pea protein isolate (PPI) contents of up to 50 % (w/w). The highest expansion and, thus, the lowest bulk density and hardness were recorded at a PPI content of 10 % (w/w). An inc...
Article
The effect of pH (4, 5, 7, and 9) combined with either heat (60, 80°C for 10 min) or pulsed electric fields (PEF) (1.4-1.8 kV/cm, 260-690 kJ/kg) treatments on the in vitro peptic digestion of ovomucin-depleted egg white was investigated. Protein digestibility, unaffected by 60°C heating, was increased by heating at 80°C, which caused protein aggreg...
Article
The volatile organic compounds (VOCs) associated with UHT milk (n = 8) inoculated with either: pure inoculums of Pseudomonas fluorescens (two strains tested), Chryseobacterium sp., or inoculums of paired cultures of the three bacterial strains, and held at 4.5 °C for up to 26 days was measured using proton transfer reaction – mass spectrometry (PTR...
Article
The importance and challenges presented by Bacillus spores in the food industry are briefly outlined with a focus on Bacillus cereus. The structure and the mechanism of resistance exhibited by Bacillus spores are described, and the steps involved in their germination are included. Novel technologies, using no or only mild heat treatments, to inacti...
Chapter
Full-text available
The meat industry is currently exploring the feasibility of using pulsed electric field processing to improve the functional properties and quality of lower value tougher meat cuts. The challenge for the meat industry is to produce products that have a standardized and guaranteed quality. This is important as attributes such as color, tenderness, a...