Water distribution in tofu and application of T2 relaxation measurements in determination of tofu's water-holding capacity

Mannoproteins modulate olfactrory perception and copigmentation of organoleptic-active-components in wines: Effects and potential molecular mechanisms

In this research, accelerated aroma release experiments and malvidin-3-O-glucoside copigmentation experiments in model red wine solutions were designed to investigate the abilities and molecular mechanisms of mannoproteins in modulating olfactory/chromatic properties of red wines. Results indicate that under orthonasal condition, mannoprotein MP2 was promising aroma modulator due to its predictable behaviors in expelling and retaining the aroma compounds during different periods. Low field nuclear magnetic resonance and molecular dynamic simulation proved that the modulation ability of MP2 should be explained by its transitionary interacting preferences with water/aroma compound molecules. Retronasal results show that the release of aroma compounds and olfactory perceptions were irregular and difficult to predict, probably due to the complexity of the retronasal condition. All mannoproteins protected malvidin-3-O-glucoside and quercetin via the formation of binary/ternary complexes, and quercetin was found prior to be protected than malvidin-3-O-glucoside. Principal mannoprotein A0A6C1DV26 might be the critical malvidin-3-O-glucoside protector. With the presence of quercetin, principal mannoproteins B3LQU1/B5VL26 in mannoprotein MP1 might exhibit intramolecular and/or intermolecular mechanisms that strengthened the hyperchromic effect, thus enhanced the copigmentation.

Two-Dimensional Laplace NMR Reconstruction through Deep Learning Enhancement

Laplace NMR is a powerful tool for studying molecular dynamics and spin interactions, providing diffusion and relaxation information that complements Fourier NMR used for composition determination and structure elucidation. However, Laplace NMR demands sophisticated signal processing algorithms such as inverse Laplace transform (ILT). Due to the inherently ill-posed nature of ILT problems, it is generally challenging to perform satisfactory Laplace NMR processing and reconstruction, particularly for two-dimensional Laplace NMR. Herein, we propose a proof-of-concept approach that blends a physics-informed strategy with data-driven deep learning for two-dimensional Laplace NMR reconstruction. This approach integrates prior knowledge of mathematical and physical laws governing multidimensional decay signals by constructing a forward process model to simulate relationships among different decay factors. Benefiting from a noniterative neural network algorithm that automatically acquires prior information from synthetic data during training, this approach avoids tedious parameter tuning and enhances user friendliness. Experimental results demonstrate the practical effectiveness of this approach. As an advanced and impactful technique, this approach brings a fresh perspective to multidimensional Laplace NMR inversion.

Translucency mechanism of heat-induced pigeon egg white gel

In this study, the properties of pigeon egg white (PEW) and chicken egg white (CEW) thermal gels were compared, with the aim of revealing the mechanisms involved in the high transparency of PEW thermal gels. Results demonstrated that PEW gels exhibited higher transparency than CEW gels. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis revealed that PEW gels formed a fine chain gel network structure with an average diameter of thermal aggregates (89.84 ± 7.13 nm). The molecular properties of PEW proteins, such as higher content of β-sheet structures (32.73 %), reactive groups (free sulfhydryl groups, hydrophobic groups), and absolute zeta potential (-3.563 mV), were found to contribute to the formation of smaller thermal aggregates during thermal denaturation. The microrheology measurements showed that these features allowed PEW proteins to interact less with each other and form smaller thermal aggregates during thermal denaturation, which facilitated the formation of fine chain gel networks and thus improved the transparency of the gels. The present study initially reveals the molecular basis of the high transparency of PEW thermal gels and provides a theoretical reference for the development of new highly transparent protein materials.

Biosynthesis, behavior and fate of volatile organic sulfide in Lentinus edodes (Berk.) upon hot-air drying treatment

This study elucidated the biosynthesis and changing behaviors of organic sulfide in shiitake mushrooms upon hot-air drying treatment. The changes of aw, moisture migration, contours of taste and flavor, organic sulfide, and 4 key enzyme activities were monitored throughout three drying procedures (CT/ST1/ST2). Results showed that drying rate was related to the moisture migration. Key enzymes of γ-GTase, ASFase and CS lyase were heat-resistant proteases, while C-Dase exhibited low thermal stability with the activity decreased during treatment. A total of 17 organic sulfides were identified and PLS analyses suggested 6 cyclic polysulfides were formed by C-Dase desulfurization, while 5 thioethers generation were related to the thermal cleavage of direct precursors (straight-chain di/tris/tetrasulfonyl esters) and Maillard reaction. These results indicated that ST2 drying procedures had a positive effect on the formation of cyclic polysulfides at the end of drying pried and the achievement of premium flavor qualities.

Multi-dimensional analysis of heat-induced soybean protein hydrolysate gels subjected to ultrasound-assisted pH pretreatment

This study aimed to evaluate the gelation characteristics of soybean protein hydrolysate (SPH) extracted by enzyme-assisted aqueous extraction. Specifically, the changes in gelation behaviors for heat-induced (95 °C, 20 min) SPH dispersions treated with pH (pH 3, 5, 9; pH 7 as control) and ultrasound (U; 240 W, 30 min) were investigated. The results showed that typical gel behavior with high elastic nature in the viscoelasticity and network structures were observed during the heating process, where the disulfide bond played a dominant role in the gel network formation of all the samples. Notably, the heat-induced aggregation in the SPH gels was mainly formed by the association of the basic B polypeptide in 11S and β subunit in 7S. The most superior SPH gel was formed at pH 7 when assisted by ultrasonication during the heating process. This as-synthesized gel showed a uniform filamentous structure and exhibited the more excellent textural, rheological and thermal properties than those of the samples formed under acidic and alkaline conditions. These results are of great value in revealing the gelation mechanism of SPH.

Steam explosion pretreatment coupling high-temperature short-time sterilization facilitating cellulose degradation and sporulation-regulatory gene expression in high-solid fermentation

Steam explosion coupling high-temperature short-time sterilization (SE-HTST) was exploited to modify cellulosic biomass medium properties and promote high-solid fermentation (HSF). Biomass characterization analysis showed that SE-HTST enlarged microstructural pores and cavities in solid media, providing more effective space for microbial growth. Meanwhile, SE-HTST helped to release glucose from the cellulose with 35.8 ± 4.5, 20.0 ± 2.3, and 12.3 ± 5.7 mg glucose/g dry medium at 24, 48, and 72 h of fermentation, which were 3.1, 2.3, and 1.5 times higher than that in medium from conventional thermal sterilization (CTS), respectively. SE-HTST increased the viable cell and spore number of Bacillus subtilis by 1.8 and 1.6 times at 72 h of fermentation compared to CTS. Moreover, the expressions of master transcriptional gene spo0A and the early sigma factors of sigF and sigE genes gradually increased in the SE-HTST medium, showing enhanced sporulation in HSF. Therefore, SE-HTST is an effective strategy for facilitating cellulose degradation, improving glucose nutrients in biomass medium, and promoting sporulation-regulatory gene expression during high-solid fermentation, which enhances the production of microbial ecological agents using B. subtilis significantly.

Structure, Merits, Gel Formation, Gel Preparation and Functions of Konjac Glucomannan and Its Application in Aquatic Food Preservation

Konjac glucomannan (KGM) is a natural polysaccharide extracted from konjac tubers that has a topological structure composed of glucose and mannose. KGM can be used as a gel carrier to load active molecules in food preservation. The three-dimensional gel network structure based on KGM provides good protection for the loaded active molecules and allows for sustained release, thus enhancing the antioxidant and antimicrobial activities of these molecules. KGM loaded with various active molecules has been used in aquatic foods preservation, with great potential for different food preservation applications. This review summarizes recent advances in KGM, including: (i) structural characterization, (ii) the formation mechanism, (iii) preparation methods, (iv) functional properties and (v) the preservation of aquatic food.

Influence of calcium sulfate incorporated with gluconolactone coagulant on the quality of whole soybean flour tofu

This work proposes a novel method for whole soybean flour tofu preparation by combining calcium sulfate (CS) and glucose-delta-lactone (GDL) coagulation. Importantly, the characteristics of the synthesized gel and the quality were studied. MRI and SEM results showed that the whole soybean flour tofu possessed satisfactory water holding capacity and water content at a CS to GDL ratio of 3:2, significantly improving the cross-linking network gel in tofu and accounting for its similar color to soybeans. Furthermore, GC-IMS analysis showed that the whole soybean flour tofu prepared at a 3:2 ratio had more flavor components (51 types) than commercially available ones (CS or GDL tofu) and exhibited satisfactory results during consumer sensory evaluation. Overall, this method is effective and applicable for the industrial preparation of whole soybean flour tofu.

Effects of drying strategies on sporulation and titer of microbial ecological agents with Bacillus subtilis

Drying operation is beneficial to the preservation and transportation of microbial ecological agents. In this study, drying kinetics and water distribution variations in solid biomass medium during hot air drying (HAD) and vacuum freeze drying (VFD) were systematically investigated. Meanwhile, the effects of different drying strategies on the sporulation of Bacillus subtilis and the titer of microbial ecological agents were compared. The results showed that both HAD and VFD induced rapid water removal from the solid biomass medium. VFD retained bound water and maintained the porous structure of the solid medium. Both HAD and VFD induced sporulation. The expression level of sporulation-regulatory genes spo0A, sigF, and sigE followed the order 80°C-HAD > 60°C-HAD > VFD. The spore number in the medium after 80°C-HAD drying for 6 h was 0.72 × 10¹⁰/g dry medium, which was 9.1 and 12.5% larger than that of the medium with 60°C-HAD and VFD, respectively. Therefore, 80°C-HAD is an effective drying strategy for promoting sporulation, which improves the titer of microbial ecological agents with B. subtilis.

The Comprehensive Utilization of Bean Dregs in High-Fiber Tofu

A large quantity of bean dregs is produced by the production of tofu and treated as animal feed or plant fertilizer, which could cause environmental pollution. The purpose of this study was to use commercially available lactone tofu to compare the effects of innovative preparation methods of high-fiber tofu, where the innovative methods used partial de-slagging followed by the addition of soybean residue cellulose to prepare high-fiber tofu. The results showed that there were no significant differences among lactone tofu samples made with 5% cellulose, 10% cellulose, or 15% cellulose and the commercially available lactone tofu during the water-holding capacity and chroma analysis. Texture indices showed that lactone tofu with 10% cellulose was similar to the commercially available lactone tofu in chewiness and hardness, and lactone tofu with 15% cellulose was similar to the commercially available lactone tofu in adhesiveness and chewiness. Magnetic resonance imaging displayed that lactone tofu with 10% cellulose had better water retention and higher moisture content. Gel electron microscopy showed that lactone tofu with 10% cellulose achieved a better gel network, and the bean dreg cellulose had less influence to a certain extent. Volatile organic compound testing by GC-IMS method indicated that the lactone tofu with 10% cellulose had more volatile organic compound content. In conclusion, these results demonstrated that lactone tofu with 10% cellulose had the best market competitiveness in ensuring the quality of high-fiber tofu.

Effects of Enzymatic Konjac Glucomannan Hydrolysates on Textural Properties, Microstructure, and Water Distribution of Grass Carp Surimi Gels

This present work investigated the influence of konjac glucomannan (KGM) enzymatic hydrolysates on the textural properties, microstructure, and water distribution of surimi gel from grass carp (Ctenopharyngodon idellus). The molecular weight (M_w) of KGM enzymatic hydrolyzed by β-dextranase degraded from 149.03 kDa to 36.84 kDa with increasing enzymatic time. In the microstructure of surimi gels, KGM enzymatic hydrolysates with higher M_w showed entangled rigid-chains, while KGM enzymatic hydrolysates with lower M_w (36.84 kDa) exhibited swelled fragments. The hardness of surimi gel with a decline in KGM M_w exhibited first increasing then decreasing trends, while the whiteness of surimi gel increased. When KGM M_w decreased, the immobile water percentage of total signals decreased from 96.7% to 93.6%, and mobile water increased from 3.03% to 6.37%. In particular, the surimi gel with the addition of K2 showed better gel strength and water distributions. KGM enzymatic hydrolysates are expected to be used as a low-calorie healthy gel enhancer in surimi processing.

Effect of hydroxychloroquine sulfate on the gelation behavior, water mobility and structure of gelatin

Hydroxychloroquine sulfate (HCQ) is a well-established antimalarial drug that has received considerable attention during the COVID-19 associated pneumonia epidemic. Gelatin is a multifunctional biomacromolecule with pharmaceutical applications and can be used to deliver HCQ. The effect of HCQ on the gelation behaviors, water mobility, and structure of gelatin was investigated to understand the interaction between the drug and its delivery carrier. The gel strength, hardness, gelling (T_g) and melting (T_m) temperatures, gelation rate (k_gel), and water mobility of gelatin decreased with increasing amounts of HCQ. The addition of HCQ led to hydrogen bonding that interfered with triple helix formation in gelatin. Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD) analysis further confirmed that the interaction between HCQ and gelatin is primarily through hydrogen bonding. Atomic force microscopy (AFM) revealed that higher content of HCQ resulted in more and larger aggregates in gelatin. These results provide not only an important understanding of gelatin for drug delivery design but also a basis for the studying interactions between a drug and its delivery carrier.

Loss of immobilized water and intense protein aggregation responsible for quality deterioration of ready to eat firm tofu

The influence of high-temperature treatment (100-120°C, 15 min) on the texture, color, and water-holding capacity of tofu gels was investigated. As the temperature increasing, the hardness and chewiness as well as the values of redness a and yellowness b increased gradually, while the water content and the lightness L value reduced progressively, and these variations were more pronounced at 115 or 120°C. Low field nuclear magnetic resonance showed that the loss of T₂₂ water led to the decrease of the water content. Scanning electron microscope revealed that the micropore in gels decreased after heating, and almost entirely disappeared at 120°C. Further analysis by SDS-PAGE indicated the soy protein aggregation formed via disulfide linkage was observed in the thermal treated tofu gels, and nondisulfide linkage might also be occurred as temperature reached 110°C or higher. The quality deterioration may be attributed to immobilized water loss combined with the protein aggregation.

Simultaneous, Rapid and Nondestructive Determination of Moisture, Fat Content and Storage Time in Leisure Dried Tofu Using LF-NMR

Leisure dried tofu is a kind of small packaged food which is popular with consumers in China. However, during the storage of leisure dried tofu, moisture and fat may be lost and deteriorate. For their own benefit, bad business operators might forge or mark the production date and shelf life. Therefore, it is necessary to explore a method to determine simultaneously the moisture, fat content, and storage time of leisure dried tofu. Samples were measured for obtaining transverse relaxation data by using low-field nuclear magnetic resonance (LF-NMR) spectrometer. The experimental data were analyzed and modeled by methods including partial least squares (PLS) or back-propagation artificial neural network (BP-ANN). The results show that the models can be used to predict the moisture, fat content, and storage time rapidly, nondestructively, accurately, and simultaneously. Furthermore, in order to explore the changes of nutrients in leisure dried tofu with the storage time, the storage dynamics of moisture and fat was considered by a using corresponding calibration model.

Effect of glycation degree on the in vitro simulated gastrointestinal digestion: A promising formulation for egg white gel with controlled digestibility

The mechanism between food gelation and its digestibility has attracted increasing attention over the past few decades. This study aimed to evaluate the effect of glycation degree on the gelation and digestibility of egg white gel (EWG) using an in vitro model and a multi-scale characterization of gel structure. Results showed that EWG glycated with increasing d-ribose by covalent bonds exhibited better gelling properties and lower in vitro digestibility according to the appearance of soluble proteins and peptides. Besides, glycation preference for ovotransferrin at lysine might be important for regulating gel structure and proteolysis accessibility via the ratio of fibrous and granular aggregates. Moreover, gel structure was predominant over amino acids modification for digestibility. Binding disorder and steric hindrance could ascribe to the lower digestibility of gels. These findings are enlightening for the formulation and production of food matrix with controlled digestibility through glycation in food and related pharmaceutical fields.

Microbial and quality improvement of boiled gansi dish using carbon dots combined with radio frequency treatment

Use of carbon dots (CDs) combined with radio frequency (RF) was applied to pasteurize and reduce the microorganism population in order to improve the quality of boiled gansi dish. CDs were prepared from banana using hydrothermal method, and characterized by using TEM, XRD and FTIR. The minimal inhibitory concentration (MIC) test showed CDs can efficiently inactivate Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis). This study also evaluated the effectiveness of five treatments, including CDs alone, CDs combined RF (CDRF) heating for different time (8 min, 12 min, and 16 min), and high pressure steam (HPS) sterilization of boiled gansi dish inoculated with B. subtilis. After CDRF treated for 8 min, 12 min, and 16 min, the center temperature of samples reached to 78.92, 87.77 and 93.82 °C, and the colony forming units (CFU) of B. subtilis reduced by 2.13, 3.62, and 4.63 log, respectively. Samples with CDRF12 treatment, exhibited better product quality as evidenced by reduced loss of texture, flavor, and sensory as compared with HPS sample. The results indicated that CDRF treatment has a great potential to produce packaged boiled gansi dish with high product quality.

Effects of native starch and modified starches on the textural, rheological and microstructural characteristics of soybean protein gel

The effects of native starch (NS), acetylated starch (AS), and acetylated distarch phosphate (ADSP) on the gel properties of soybean protein thermal gel were investigated using texture analysis, low-field nuclear magnetic resonance (LF-NMR) spectroscopy, dynamic rheometry and scanning electron microscopy. The results of the textural profile analysis showed that 10% ADSP increased the hardness and chewiness of the mixed gel, while NS and AS led to decreases in the textural properties. The results of the LF-NMR analysis indicated that the AS improved the water-holding capacity of the mixed gel due to the transformation of weakly bound water to strongly bound water. During heating and cooling, the rheological profiles of the elastic (G') and viscous modulus (G″) of all the samples exhibited a two-stage pattern of decrease and then increase, and the final values of G' and G″ reached maxima when the ADSP content was 10%. The scanning electron microscopy images showed that the ADSP granules dispersed in the gel network. The integrity of the starch granules was crucial for regulating the properties of the soybean protein gel. These results provided information about the further design and preparation of soybean protein foods containing modified starch.

Enhancement of Bacillus subtilis Growth and Sporulation by Two-Stage Solid-State Fermentation Strategy

Two-stage solid-state fermentation strategy was exploited and systematically optimized to enhance Bacillus subtilis growth and sporulation for increasing effective cell number in B. subtilis microbial ecological agents. The first stage focused on improving cell growth followed by the second stage aiming to enhance both cell growth and sporulation. The optimal fermentation condition was that temperature changed from 37 °C to 47 °C at a fermentation time of 48 h and Mn2+ content in medium was 4.9 mg MnSO4/g dry medium. Solid medium properties were improved by the optimal two-stage fermentation. HPLC results demonstrated that glucose utilization was facilitated and low-field nuclear magnetic resonance (LF-NMR) results showed that more active sites in medium for microbial cells were generated during the optimal two-stage fermentation. Moreover, microbial growth and sporulation were enhanced simultaneously during the second stage of fermentation through delaying microbial decline phase and increasing sporulation rate. As a result, effective cell number of B. subtilis reached 1.79 × 1010/g dry medium after fermentation for 72 h, which was 29.7% and 8.48% higher than that of conventional fermentation for 72 h and 48 h, respectively. Therefore, the optimal two-stage fermentation could increase the effective cell number of B. subtilis microbial ecological agents efficiently.

Investigation on characteristics of 3D printing using Nostoc sphaeroides biomass

BACKGROUND

Gel-like constructs can be produced using an extrusion-based 3D food printing (3D-FP) technique. Nostoc sphaeroides biomass is a natural gel material. Considering its good nutrition and rheological properties, these algae were chosen in this study as supply material (ink) for 3D-FP. With this gel material, the extrusion-based 3D printing system was set as a model, and the printing behavior was investigated. Furthermore, the 3D-FP mechanisms were explained through low-field nuclear magnetic resonance and rheological measurements.

RESULTS

Results indicated that although fresh biomass gel was printable, non-uniformity and instability occurred during printing. Blanched inks showed non-smooth printing behavior, which was associated with a decrease in elasticity and viscosity. Printability was improved by increasing the rehydration time to 24 h when rehydrated powder was used. Increasing the rehydration time increased the water-binding degree. Pre-gelatinized potato starch was added to the mixture at ratios ranging from 1 to 100 g kg^-1 . The best printing outcome was observed at 40 g kg^-1 potato starch.

CONCLUSION

We emphasize that elasticity and viscosity balance is an essential parameter to achieve printability. The strategies adopted in this work provide new insights into the development of personalized food regarding texture and nutritional additive content. © 2018 Society of Chemical Industry.

Effect of microparticulation and xanthan gum on the stability and lipid digestion of oil-in-water emulsions stabilized by whey protein

Since lipid digestion is an interfacial process, food emulsions are increasingly being seen as a mechanism for controlling lipid uptake.

Rapid and non-invasive detection and imaging of the hydrocolloid-injected prawns with low-field NMR and MRI

Method development for monitoring economically motivated food adulteration is pivotal for preventing health problems caused by illegal food additives. In this work, low-field nuclear magnetic resonance (LF-NMR) spectroscopy and magnetic resonance imaging (MRI) was applied for the detection and mapping of adulterated prawns injected with different hydrocolloids including gelatin, carrageenan, agar, amorophophallus konjac and xanthan gum. The characteristic T₂ fitting curves were obtained which can be used to tell apart adulterated prawns from normal ones. Furthermore, the benefit from high quality LF-MRI images showed the major accumulation site of the hydrocolloids injected in prawn. The location of these injections was mainly confined to well resolved accumulation in brain region and three following subtle sites: back, tail and claws. Different hydrocolloids can be successfully distinguished in adulterated prawns with principal component analysis. Therefore, rapid, non-invasive and low-cost LF-NMR technique offers a powerful tool for the identification of hydrocolloids adulteration in real-time.