•Ionic and hydrogen bonds had little participation in wheat gluten gel formation.•Disulfide bonds and hydrophobic interactions contributed to gel formation.•Wheat gluten unfolded and reorganized ...during gelation.•A three-dimensional network formed at gelling temperatures greater than 60°C.
In order to elucidate the heat-induced wheat gluten gel formation mechanism, changes in chemical interactions and protein conformation were investigated during gelation. The contribution of ionic and hydrogen bonds were found to decrease from 0.746 and 4.133g/L to 0.397 and 2.733g/L, respectively, as the temperature increased from 25 to 90°C. Moreover, the free SH content remarkably decreased from 37.91 to 19.79μmol/g during gelation. Ultraviolet absorption spectra and intrinsic fluorescence spectra suggested that wheat gluten unfolded during the heating process. In addition, wheat gluten gels treated at 80 and 90°C exhibited a “steric hindrance” effect, which can be attributed to the formation of aggregates. Fourier transform infrared spectra suggested that the random coil content increased at low temperatures (40 and 50°C), whereas the content of intermolecular β-sheets due to protein aggregation increased from 38.10% to 44.28% when the gelation temperature was 90°C.
Phenolics are good natural antioxidant in human diets and contribute to formation of sensory attributes of food products. This study aimed to investigate effects of 1%–5% pomegranate juice powder ...(PJP, rich in phenolics) used as sugar in fermentation matrix on the physiochemical properties (color, sensory and total phenolic content), structure (texture and microstructure), rheology and functionality (antioxidant activity and in vitro bioaccessibility) of set yogurts during storage for 21 days. It showed that the higher PJP level, the higher sensory scores and total phenolic contents the yogurt had, the firmer in texture and compacter in microstructure became, and the better viscoelasticy and stronger antioxidant activity exhibited. But there was no significant difference (P > 0.05) in color and bioaccessibility between controls and yogurts with PJP. During the storage, except for the consistency of LD was slightly lower than that of the control on the first day and at the end of storage, the values of other quality attributes of the LD, MD, MD groups showed higher than that of the controls. Results indicated that 5% PJP has potential to improve quality attributes of set yogurt by replacing sucrose in fermentation matrix.
•1%–5% pomegranate juice powder (PJP) was used as a sugar replacer for set yogurts production.•PJP improved gel viscoelasticity, antioxidant activity and storage stability of set yogurts.•Enhancement effects on set yogurts increased with the increasing levels of PJP replacement.•PJP can replace some or all sucrose in fermentation matrix for the production of functional yogurt.
To evaluate infrared radiation (IR) blanching in comparison to conventional hot water (HW) blanching in inhibiting the browning and extending the shelf life of pecan kernels, the technology of IR ...blanching at 500–700 W for 90–45 s or HW blanching at 90°C for 60 s, and subsequently drying with hot air at 60, 70, and 80°C, respectively, was used, and then the activities of lipoxidase (LOX) and polyphenol oxidase (PPO), antioxidant capacities, color change, microscopic structure, and the shelf life of kernels were analyzed. Results showed that IR blanching not only significantly decreased the subsequent drying time but also effectively inactivated the activities of LOX and PPO, showing a lower residual activity of 15.74%–40.41% and 16.75%–56.25%, respectively. A higher retention of total phenolics was observed in kernels subjected to IR blanching, from 25.03 ± 0.04 to 29.50 ± 0.96 mg GAE/g compared with HW blanching (14.43 ± 0.07 mg GAE/g). Meanwhile, IR‐blanched samples showed lower peroxide values, p‐anisidine values, total color difference values, browning index, quinones contents, and lipofuscin‐like pigments levels but had higher 2,2‐diphenyl‐1‐picrylhydrazyl inhibition rate and better storage stabilities than HW‐blanched samples. The technology of IR blanching at 600 W for 60 s followed by drying with hot air at 70°C for 40 min is suitable for producing pecan kernels with better qualities and a longer shelf life, through inactivating the endogenous enzymatic reactions and inhibiting the formation of lipofuscin‐like pigments.
Practical Application
Blanching is an essential pretreatment of food processing. Conventional blanching is achieved by hot water, which has some disadvantages of low‐intensity enzyme inactivation, loss of water‐soluble substances, etc. In this study, the potential of using infrared blanching, prior to drying, was studied to find solutions to improve the nutritional value, and the shelf life of pecan kernels. The results showed that infrared blanching at 600 W for 60 s followed by drying with hot air at 70°C for 40 min could inhibit the color degradation, improve the oxidation resistance, and prolong the shelf life of kernels.
Oleogels were prepared by emulsion template method through 3.0% tea polyphenol ester (Tp‐ester) particles with four fatty acid chain length (Tp‐laurate C12, Tp‐myristate C14, Tp‐palmitate C16, and ...Tp‐stearate C18) and 2.5% citrus pectin, and then were used in cookie production as fat replacer. Effects of the fatty acid chain length on the hydrophilicity/hydrophobicity of Tp‐ester, on the appearance, microstructure, and firmness of dried products, on rheological features of oleogels, on the dynamic viscoelasticity and textural characteristics of cookies dough, and on cookies qualities were revealed. With the increase in the fatty acid chain length, the θo and θw values of four Tp‐esters increased, the firmness of dried products with smaller oil droplets got larger, and the gel intensity of oleogels increased, but the quality scores, spread ratio, and break strength of the cookies did not change significantly. With the increase in the replacement levels of butter with oleogels, the harder cookie dough with weaker gel strength and the softer cookies with lower hedonic scores and crispness were found. At 25% and 50% replacement levels, cookies prepared with oleogels using Tp‐palmitate or Tp‐stearate particles exhibited similar hedonic scores, break strength, spread ratio, and storage stabilities to that of butter cookies.
Practical Application
Cookies are relished by all age groups due to their taste and crispness, but include high content of saturated fatty acids that are harmful to people's health. The result of this study will help the industry to better design cookies through oleogels with tea polyphenols ester and pectin, and will provide healthy cookies with little or no butter for consumers.
To improve tofu quality, the effects of using 0.12–0.18 g/100 mL citric acid, l-(-)-malic acid, or tartaric acid as coagulation agents were investigated. The results showed that storage modulus, ...hardness, water-holding capacity, non-freezable water content, and in-gel hydrophobic interactions were optimal when tofu was prepared with 0.14 g/100 mL organic acids, but deteriorated when more than 0.16 g/100 mL was used. Slower acidification during gelling in the presence of 0.14 g/100 mL organic acid promoted protein–protein hydrophobic interactions, resulting in a higher elastic modulus. Moreover, the tofu products showed higher water-holding capacity and non-freezable water content, as well as more compact gel microstructures. Notably, tofu prepared with citric or l-(-)-malic acid was of better quality than tofu prepared with tartaric acid. Collectively, the results demonstrate that soft or firm tofu with desirable physicochemical properties can be prepared with organic acids if acidification is adequately controlled during gelation.
•Acidification rate during coagulation critically impacts tofu quality.•Gentler acidification promotes hydrophobic interactions.•Stronger hydrophobic interactions increase non-freezable water content.•Stronger hydrophobic interactions also improve tofu texture.•Stronger protein-protein interactions generate a more compact tofu microstructure.
•Soy protein isolate (SPI) and wheat gluten (WG) exhibit poor individual gelation.•Ultrasonic pretreatment improved MTGase-induced SPI/WG mixture gelation properties.•Ultrasonic treatment reduced the ...particle size of SPI/WG molecules.•Ultrasonic treatment increased SPI/WG gel water holding capability and gel strength.•SPI/WG gel had denser, more homogeneous protein networks after ultrasonic treatment.
Soy protein isolate (SPI) and wheat gluten (WG) are widely used in commercial food applications in Asia for their nutritional value and functional properties. However, individually each exhibits poor gelation. In this study, we examined the microbial transglutaminase (MTGase)-induced gelation properties of SPI and WG mixtures with high intensity ultrasonic pretreatment. Ultrasonic treatment reduced the particle size of SPI/WG molecules, which led to improvements in surface hydrophobicity (Ho) and free sulfhydryl (SH) group content. However, MTGase crosslinking facilitated the formation of disulfide bonds, markedly decreasing the content of free SH groups. Ultrasonic treatment improved the gel strength, water holding capacity, and storage modulus and resulted in denser and more homogeneous networks of MTGase-induced SPI/WG gels. In addition, ultrasonic treatment changed the secondary structure of the gel samples as determined by Fourier transform infrared spectroscopic analysis, with a reduction in α-helices and β-turns and an increase in β-sheets and random coils. Thus, ultrasound is useful in facilitating the gelation properties of MTGase-induced SPI/WG gels and might expand their utilization in the food protein gelation industry.
