Effects of Laccase and Transglutaminase on the Physicochemical and Functional Properties of Hybrid Lupin and Whey Protein Powder.

Plant-based protein is considered a sustainable protein source and has increased in demand recently. However, products containing plant-based proteins require further modification to achieve the desired functionalities akin to those present in animal protein products. This study aimed to investigate the effects of enzymes as cross-linking reagents on the physicochemical and functional properties of hybrid plant- and animal-based proteins in which lupin and whey proteins were chosen as representatives, respectively. They were hybridised through enzymatic cross-linking using two laccases (laccase R, derived from Rhus vernicifera and laccase T, derived from Trametes versicolor) and transglutaminase (TG). The cross-linking experiments were conducted by mixing aqueous solutions of lupin flour and whey protein concentrate powder in a ratio of 1:1 of protein content under the conditions of pH 7, 40 °C for 20 h and in the presence of laccase T, laccase R, or TG. The cross-linked mixtures were freeze-dried, and the powders obtained were assessed for their cross-linking pattern, colour, charge distribution (ζ-potential), particle size, thermal stability, morphology, solubility, foaming and emulsifying properties, and total amino acid content. The findings showed that cross-linking with laccase R significantly improved the protein solubility, emulsion stability and foaming ability of the mixture, whereas these functionalities were lower in the TG-treated mixture due to extensive cross-linking. Furthermore, the mixture treated with laccase T turned brownish in colour and showed a decrease in total amino acid content which could be due to the enzyme's oxidative cross-linking mechanism. Also, the occurrence of cross-linking in the lupin and whey mixture was indicated by changes in other investigated parameters such as particle size, ζ-potential, etc., as compared to the control samples. The obtained results suggested that enzymatic cross-linking, depending on the type of enzyme used, could impact the physicochemical and functional properties of hybrid plant- and animal-based proteins, potentially influencing their applications in food.

Identifying sensory attributes of Korean rice wine (makgeolli) using sensory evaluation and chemical analysis.

Makgeolli is a traditional alcoholic beverage in Korea; however, research on makgeolli is limited in foreign markets such as New Zealand. This study seeks to identify sensory descriptors that best describe makgeolli among New Zealand consumers. Four methods of making makgeolli have been identified based on different processing times and the number of fermentation stages. Chemical analysis and sensory evaluation were carried out to establish the different sensory and flavor properties of the four different makgeolli samples. Chemical analysis using SPME-GC-MS was employed to understand the volatile compounds present in the four makgeolli samples, while two sensory tests were carried out simultaneously using Check-All-That-Apply (CATA) and Just-About-Right (JAR). A total of 45 volatile compounds were identified using SPME-GC-MS, and examples of major volatiles include 2-methyl-1-propanol (alcoholic flavor), limonene (citrus-like flavor), and hexanal (green/grass-like flavor). One hundred and twenty-nine subjects (n = 68 females) completed the sensory evaluation and were analyzed for this study. Female subjects tend to rate overall acceptance of makgeolli higher than male subjects; both subjects preferred 1SF-YN with the highest mean hedonic score, and the least preferred makgeolli was 1SF-N. From CATA, attributes such as apple, apricot, peach, sweet taste, and bubbly texture were statistically significant when describing makgeolli. For JAR, a high proportion of subjects indicated that sourness was too much in three of the four makgeolli samples. PRACTICAL APPLICATION: Research on rice wine in Western markets such as New Zealand is limited, and this study gives insight into how New Zealand consumers perceive Korean rice wine (makgeolli). Sensory participants in this study indicated that makgeolli is too sour and lacks sufficient sweetness in the majority of the samples examined. When launching makgeolli to the New Zealand market, practitioners need to optimize sweetness and reduce sourness to increase overall liking. Sensory terms used by subjects describing makgeolli include cider, apple, and sour.

Characterisation of Korean rice wine (makgeolli) prepared by different processing methods.

Four methods of preparing makgeolli, a traditional Korean turbid rice wine, were reported in this study. The four processing routes include single-stage simultaneous saccharification and fermentation of glutinous rice with nuruk - a Korean starter culture (1SF-N), single-stage fermentation with nuruk and yeast (1SF-YN), two-stage fermentation (2SF) and three-stage fermentation (3SF). Chemical analysis was used to determine how the different processing routes could affect the rice wine's properties in terms of alcohol content, pH, colour, mineral content, proximate composition, antioxidant activity, total phenolic content, sugar, free amino acid, and organic acid profile. Sensory analysis using polarised projective mapping (PPM) and 62 participants found that sweetness is the most desirable attribute for makgeolli among New Zealand consumers with sourness and bitterness as less desirable. The 2SF makgeolli sample had the highest concentration of glucose (8.2 mg/mL) and maltose (107 mg/mL) and in the PPM experiment was the most preferred out of the four processing methods. The 1SF-N makgeolli sample had the highest alcohol (13% ABV), crude protein (4.9%), antioxidant activity, total phenolic (621 mg GAE/L) and free amino acids content, however, it was the least overall liked makgeolli sample. Overall, the novelty of this research includes formulating a traditional Korean turbid rice wine in a Western country environment and evaluating consumer perception of makgeolli beyond the normal clientele in South Korea. From these results it is suggested that the properties of makgeolli can be manipulated via processing to suit the brewer's sensory needs that best fits the consumer market.

Lactic fermentation of cooked, comminuted mussel, Perna canaliculus.

The endogenous microflora of mussels, filter feeders, can include pathogens with resulting food safety concerns. The aim was to develop a cook-then-ferment technology to extend shelf life and safety of a ready-to-eat mussels. Only after cooking to destroy the mussel's endogenous microflora could an edible product be made as determined by pH decline after fermentation and the fate of common pathogens. Perna canaliculus was bought live at retail on many dates. Fermentation was with commercial lactic cultures incubated under vacuum at 30 °C for four days. Using one culture containing Pediococcus pentosaceus and Staphylococcus carnosus as a model, pH typically declined to 4.5 to 4.7, and common pathogens, Staphylococcus aureus, Salmonella and Vibrio parahaemolyticus were absent or reduced to acceptable levels. The fate of Listeria monocytogenes was studied with five cultures. These were variably effective at inhibition with one clear success, Chr Hansen's T-SC-150 containing a specific strain of Lactobacillus sakei, and flavour-generating Staphylococcus carnosus. This culture's efficacy was confirmed with sterile extracts of LAB challenging L. monocytogenes in vitro. This culture was also the most rapid fermenter by pH fall. Cook-then-ferment technology may be applied to other novel foods to minimise a disruptive endogenous microflora.

Kinetics of conversion of dihydroxyacetone to methylglyoxal in New Zealand manuka honey: Part V - The rate determining step.

Monomer formation from dimeric DHA has previously been suggested as the rate-determining step in formation of methylglyoxal, the bioactive component in manuka honey. This step was studied by 1H NMR in DMSO­d6. First order reaction rate was 3.31 × 10-3 ±â€¯9.1 × 10-4 min-1. Upon titration with D2O, little change was observed until ∼15 mass% whereupon an exponential increase in rate occurred until indistinguishable from the rate observed in water. Acid or base caused rate accelerations. Theoretical modelling confirmed the existence of acid and base-catalysed mechanisms for dimer decomposition and the structures of two intermediates observed. In honey it is likely the base-catalysed decomposition predominates with water as catalyst but there is little rate acceleration at the levels of water present normally in honey however a small increase in the mass% of water in the honey could cause significant rate acceleration of dimer decomposition and hence formation of methylglyoxal.

Kinetics of conversion of dihydroxyacetone to methylglyoxal in New Zealand manuka honey: Part IV - Formation of HMF.

During a study of the conversion of dihydroxyacetone (DHA) to methylglyoxal (MGO) in maturing New Zealand manuka honey, the kinetics of formation of 5-(hydroxymethyl)furfural (HMF) was studied at temperatures from 4 to 37°C. Formation of HMF was first-order during an induction period and zero-order thereafter indicating that the mechanism includes the formation of certain critical intermediates and that these require time to build up; the duration of the induction period depended primarily upon temperature. The zero-order rate constant at 37°C was the same for manuka honey and clover honey doped with 2000 or 10,000mg/kg DHA and for artificial honey with 2000mg/kg of DHA and either alanine or proline and alanine added. Zero-order rate constants for artificial honey with added amino acids were less than for a control without amino acids. A simulation was created to predict the formation of HMF over time at 37°C in manuka honey.