Effects of a cross-linking enzyme on the protein composition, mechanical properties, and microstructure of Chinese-style noodles

Effect of a Bacterial Laccase on the Quality and Micro-Structure of Whole Wheat Bread

The gluten protein content in whole-wheat flour is low, which affects the elasticity and viscosity of the dough. Enzymatic modification of the protein may result in a network that mimics gluten, which plays an important role in the processing of whole-wheat foods. In this study, the effects of Halomonas alkaliantartica laccase (LacHa) on the quality parameters of whole-wheat bread were investigated. The optimum dosage of LacHa was 4 U/100 g of whole-wheat flour. At this dosage, whole-wheat bread exhibited the best specific volume and optimum texture parameters. Laccase also extended the storage duration of whole-wheat bread. We analyzed the micro-structure of the dough to determine its gluten-free protein extractable rate and free sulfhydryl group content, and verify that LacHa mediates cross-linking of gluten-free proteins. The results demonstrated that the cross-linking of gluten-free protein by LacHa improves the texture of whole-wheat bread. As a flour improver, LacHa has great developmental and application potential in baked-food production.

The Effects of Transglutaminase and Refrigerated Storage on the Physicochemical Properties of Whole Wheat Dough and Noodles

This study investigated the effects of transglutaminase (TG) concentrations (0, 0.1% and 1%) on the physicochemical properties of whole wheat dough (WWD) and noodles (WWN) during refrigerated storage (0, 1, 2, and 3 days). The yield, ferulic acid (FA) content, molecular weight (Mw), and apparent viscosity (AV) of water extractable arabinoxylan (WEAX) from refrigerated WWDs were analysed. The WEAX yield and FA tended to increase with refrigerated storage, while the Mw decreased. WEAX FA of from WWD with TG tended to be smaller than the control during refrigeration. The AV for all WEAXs gradually decreased during refrigeration. The TG concentration effects on WWD resistance to extension and extensibility and the WWN cooking properties and texture profile analysis (TPA) were studied. The water absorption and swelling index tended to decrease in WWNs with TG depending on refrigeration time compared to the control samples. The TPA results showed that WWNs with TG were significantly harder than the control after two days of refrigeration. This study demonstrated that TG affected not only WWD composition but also WWN physical properties during refrigerated storage.

Potential application of enzymes to improve quality of dry noodles by reducing water absorption of inferior-quality flour

This study has investigated the characteristics of dry noodles made with Korean domestic wheat flours using enzyme treatment for reducing water absorption to improve noodle-making performance. The water solvent retention capacity (SRC) values of flour treated with α-amylase and xylanase significantly decreased with increasing enzyme concentrations up to 0.025% (flour weight basis), which confirmed the enzyme effect on reducing the water absorption capacity of damaged starches and arabinoxylans. Enzyme-treated cooked noodles showed changes in textural characteristics, depended on the enzyme type, water amount, and drying method. Applying α-amylase for reducing the water absorption capacity of flour could mitigate the issue of inferior dry-noodle-making performance. Sensory evaluation showed improved preference attributes of cooked noodles with α-amylase treatment. In conclusion, the α-amylase application could improve the quality of dry-noodle made of Korean domestic wheat flour by diminishing the undesirable effect of damaged starch in flour related to noodle quality.

Enzymatic modifications of gluten protein: Oxidative enzymes

Oxidative enzymes treat weak flours in order to restore the gluten network of damaged wheat flour and reduce the economic and technological losses. The present review concentrates on oxidative exogenous enzymes (transglutaminase, laccase, glucose oxidase, hexose oxidase) and oxidative endogenous enzymes (tyrosinase, peroxidase, catalase, sulfhydryl oxidase, lipoxygenase, lipase, protein disulfide isomerase, NAD(P)H-dependent dehydrogenase, thioredoxin reductase and glutathione reductase) and their effects on the rheological, functional, and conformational features of gluten and its subunits. Overall, transglutaminase is used in wheat-based foods through introducing isopeptide bonds (ε-γ glutamyl-lysine). Glucose oxidase, hexose oxidase, peroxidase, sulfhydryl oxidase, lipase, and lipoxygenase form disulfide and nondisulfide bonds through producing hydrogen peroxide. Laccase, tyrosinase, and protein disulfide isomerase form cross-links between tyrosine and cysteine residues by generating radicals. Thioredoxin reductase and glutathione reductase create new inter disulfide bonds. The effect of oxidative enzymes on the formation of covalent cross-linkages were substantially more than non-covalent bonds in gluten structure.

Effects of Transglutaminase on the Protein Network and In Vitro Starch Digestibility of Asian Wheat Noodles

Wheat noodles are a staple commonly consumed in Asia, but high intakes have been associated with type 2 diabetes due to its rapid starch digestibility. We hypothesised that protein network-binding via transglutaminase (TG) would form a stronger barrier encapsulating the starch granules to limit enzymatic access and digestion. The amount of glucose release decreased significantly with increasing TG concentration, with a reduction of approximately 16% with 2% TG after 120 min of digestion. The slower rate of glucose release during the first 60 min of digestion for 2% compared to 0% TG suggested impeded first stage enzymatic access rather than second stage starch hydrolysis into glucose. Upon increasing the TG concentration, confocal microscopy revealed a denser protein network with increased connectivity, supported by a decrease in protein solubility and gelatinisation enthalpy, and increased firmness and work of shear. Therefore, transglutaminase can potentially be used to reduce starch digestibility in wheat noodles via protein network-binding.

Effect of Thermostable α-Amylase Addition on Producing the Porous-Structured Noodles Using Extrusion Treatment

Problems with rehydration and palatability are considered as unacceptable quality characteristics for the noodles produced using high-strength extrusion technique. Thus, the aim of this study was to solve these problems by designing a novel method to create a porous structure for the high-strength extruded noodles (HENs). The quality indices of HENs were significantly improved after adding to them thermostable α-amylase (TαA) at 0.05% to 0.10%. The microstructure graphs showed that a well-developed porous structures was successfully created throughout noodle strands. This indicated that the TαA has effectively worked on starch granules in spite of the high-strength performance of the extrusion process. MALLS-GFC, X-ray diffraction, and differential scanning calorimeter investigations showed that the appearance of a porous structure was mainly attributed to the internal collapse of α-1,4-glycosidic bonds and the dissolution of water-soluble degradation products, such as dextrin and oligosaccharides. Moreover, the slight inhibited effect of excess TαA on the starch gelatinization was because of the fact that the high enzyme concentration might cause TαA to adhere or overlay on it.

PRACTICAL APPLICATION

The rehydration and palatability properties of HENs were greatly improved by creating a well-developed or honeycomb-like porous structure using TαA at low concentration. The findings of this study could be applied to enhance the quality characteristics of HENs and to encourage the research and development in the noodle industry.

Microbial transglutaminase in noodle and pasta processing

Nowadays, there is an aggressive rate in consumption of noodles and pasta products throughout the world. Consumer acceptability and preference of these functional products can be promoted by the discovery of novel knowledge to improve their formulation and quality. The development of fortified-formulations for noodles and pasta products based on microbial transglutaminase (MTGase) can guarantee the shelf life extension with minimum quality losses. The current review focuses on recent trends and future prospects of MTGase utilization in the structural matrix of noodles and pasta products and represents the quality changes of cooking loss, texture, microstructure, color and sensory attributes of the MTGase-incorporated products. Digestibility, nutritional and health aspects of the MTGase-enriched formulations are also reviewed with a vision toward physical functions and safety outcomes of MTGases isolated from new microbial sources. The high potential of MTGase in developing commercial noodles and pasta products is successfully demonstrated. MTGase by modifying the crystallinity or molecular structure via covalent crosslinks between protein molecules strengthens the doughs stability and the textural characteristics of final products with the low- or high-protein flour. Compared with the control samples, the MTGase-supplemented products indicate slower digestion rates and better sensory and cooking properties without any remarkable color instability.

Determination of mercury, cadmium and lead contents in different tea and teas infusions (Camelia sinensis, L.)

The present paper deals with assessing the level of contamination of green (n = 14) and black - fermented (n = 10) teas of different origins (country of origin) (China, India, Japan, Nepal and Taiwan), which are normally available in Slovakia. The contents of the studied contaminants (mercury, cadmium and lead) were observed in samples of dried teas and their infusions. The contaminant contents were investigated by atomic absorption spectrometry with Zeeman background correction and a graphite furnace GF-AAS (Cd, Pb). The total mercury content was analyzed by CV-AAS method. Concentrations of the studied contaminants in the dried tea samples were as follows: green tea: Hg: 0.0027 ±0.0010 mg.kg-1 (median ± standard deviation); Cd: 0.161 ±0.084 mg.kg-1, Pb: 0.875 ±0.591 mg.kg-1, black tea: Hg: 0.0022 ±0.0014 mg.kg-1, Cd: 0.397 ±0.077 mg.kg-1, Pb: 1.387 ±0.545 mg.kg-1. The contents of the contaminants in the tea infusions were as follows: green tea: Hg: 0.03 ±0.04 μg.L-1, Cd: 0.278 ±0.068 μg.L-1, Pb: 1.975 ±0.503 μg.L-1, black tea: Hg: 0.050 ±0.080 μg.L-1, Cd: 0.291 ±0.054 μg.L-1, Pb: 1.955 ±1.264 μg.L-1. According to the currently valid maximum limits for a particular contaminant in Slovakia, it can be stated that the health standards were not exceeded in any of the tea samples. The limit value of the lead content (2.0 mg.kg-1 DM) was exceeded (by 12.4%) only in one sample of the dried black tea from China (Yunnan - Golden Snow), however it is the limit value valid in China. The results of the analysis of 24 tea samples show that even regular consumption does not pose a health risk to consumers.