Changes in Properties of Soy Protein Isolate Edible Films Stored at Different Temperatures: Studies on Water and Glycerol Migration

Storage stability of konjac glucomannan/curdlan films at low temperature and its coating for the preservation of cucumbers

Fruits and vegetables suffer severe moisture loss during cold storage. To explore the mechanism of water transfer, this study investigated the properties of konjac glucomannan (KGM)/curdlan (KC) composite films after cold storage treatment, the preservation of KC-coated cucumbers, and the water transfer. The results showed that the weight, thickness, free water content, and enthalpy (ΔH) of endothermic peak of the film increased after cold storage, mainly because of the water adsorption and diffusion. K6C4 (the KGM/curdlan mass ratio in 6:4) maintained uniform and dense and showed the lowest dissolution loss of 21.92%. Moreover, the water content of K6C4 film changed by 1.1% on day 15, and K6C4 exhibited excellent gas barrier and mechanical properties. These were attributed to the optimal matrix formed by the assembly of KGM and curdlan in K6C4, contributing to the stability of structure and performance. K6C4 coating significantly maintained the quality of cucumbers. At the end of storage, the firmness and weight loss of the coating group were 19.3% and 24.4% higher than the control group, respectively. The color, total solid content, acid, and VC were maintained for coating group. The low-field nuclear magnetic resonance revealed that K6C4 coating inhibited the water transfer from the center to the epidermis of cucumbers by blocking the water produced by respiration and the free water in the tissues. The storage stability and water transfer analysis will contribute to the understanding of the mechanism of coating inhibiting moisture loss of fruits and vegetables.

Effect of freeze-thaw cycles on the quality of Yuba with different protein-lipid ratios on its protein-lipid network system

We investigated the effects of freeze-thaw (FT) cycles on the quality of Yuba with different protein-lipid ratios and on its protein-lipid network system in this study. The water holding capacity (WHC), tensile strength (TS), and L* values decreased significantly and elongation at break (EAB), b* values, carbonyl and Thiobarbituric acid value (TBARS) increased significantly after FT treatment. The variation in Yuba quality weakened after the 4 FT. Ice crystals disrupt the structure of the protein network, resulting in a degradation of Yuba quality. The degradation of Yuba quality was slowed by the influence of the contraction of the protein network at a later period. The formation of a weaker protein network and the high lipid content in low protein-lipid ratios led to a new trend of higher L* than the high protein-lipid. The results showed that a high protein-lipid ratio improved the FT stability of Yuba.

Impact of environmental storage conditions on properties and stability of a smart bilayer film

This study aimed to investigate the behavior of smart bilayer films under various temperature and relative humidity (RH). Smart bilayer films were fabricated using sodium alginate with incorporated butterfly pea anthocyanin and agar containing catechin-lysozyme. Cellulose nanospheres were added at concentrations of 0% and 10% w/w of the film and subjected to test at 4 °C and 25 °C, considering different RHs (0%, 50%, and 80%). The results showed that RH had a greater impact on the mechanical properties than temperature, leading to a decrease in tensile strength and an increase in elongation at break with higher RH. The films displayed increased strength but reduced flexibility at low temperatures. Oxygen permeability was negatively affected by increasing RH, while water vapor barrier properties were better at 25 °C than at 4 °C. In terms of color stability, the temperature played a more important role, with both types of smart bilayer films retaining their color stability throughout 14-day storage at 4 °C, even maintaining their ability to change color with pH. However, the films stored at 25 °C exhibited lower color stability and showed potential for color change with varying pH levels, but with lower intensity. The findings of this study demonstrate the significant impact of temperature and RH on the functional properties of smart bilayer films, with and without the addition of cellulose nanospheres. Such smart bilayer films have great potential for various applications, particularly in food packaging, where maintaining color, mechanical, and barrier properties under varying environmental conditions is crucial.

Eco-Friendly Straws: A Fusion of Soy Protein Isolate and Cassava Starch Coated with Beeswax and Shellac Wax

This research aimed to produce eco-friendly straws using soy protein isolate (SPI) and cassava starch (CS) at different ratios by the extrusion technique and by coating with beeswax and shellac wax. Three straw formulations (F) (F1: 24.39% SPI-24.39% CS; F2: 19.51% SPI-29.37% CS; and F3: 14.63% SPI-34.15% CS) were prepared, incorporating glycerol (14.6% w/w) and water (36.6% w/w). After extrusion and drying at 80 °C for 20 h, visual assessment favored F2 straws due to smoother surfaces, the absence of particles, and enhanced straightness. For the physical property test, the straws were softened in pH buffer solutions for 5 min. To simulate practical application, mechanical bending strength was studied under different relative humidity (RH) settings. Water absorption reduced the strength as RH increased. F2 straws outperformed other formulations in bending strength at 54% RH. For hydrophobic coatings, F2 was chosen. Beeswax- and shellac wax-coated straws displayed negligible water absorption and sustained their integrity for over 6 h compared to uncoated straws. This study shows that extrusion and natural coatings may make sustainable straws from SPI and CS. These efforts help meet the growing demand for eco-friendly plastic alternatives, opening up new options for single-use straws.

Moisture loss inhibition with biopolymer films for preservation of fruits and vegetables: A review

In cold storage, fruits and vegetables still keep a low respiratory rate. Although cold storage is beneficial to maintain the quality of some fruits and vegetables, several factors (temperature and humidity fluctuations, heat inflow, air velocity, light, etc.) will accelerate moisture loss. Biopolymer films have attracted great attention for fruits and vegetables preservation because of their biodegradable and barrier properties. However, there is still a certain amount of water transfer occurring between storage environment/biopolymer films/fruits and vegetables (EFF). The effect of biopolymer films to inhibit moisture loss of fruits and vegetables and the water transfer mechanism in EFF system need to be studied systematically. Therefore, the moisture loss of fruits and vegetables, crucial properties, major components, fabrication methods, and formation mechanisms of biopolymer films were reviewed. Further, this study highlights the EFF system, responses of fruits and vegetables, and water transfer in EFF. This work aims to clarify the characteristics of EFF members, their influence on each other, and water transfer, which is conducive to improving the preservation efficiency of fruits and vegetables purposefully in future studies. In addition, the prospects of studies in EFF systems are shown.

Preparation of glucoamylase microcapsule beads and application in solid-state fermentation

BACKGROUND

Baijiu brewing adopts the solid-state fermentation method, using starchy raw materials, Jiuqu as saccharifying fermenting agent, and distilled spirits made by digestion, saccharification, fermentation and distillation. In the late stages of solid-state fermentation of Baijiu, the reduced activity of glucoamylase leads to higher residual starch content in the Jiupei, which affects the liquor yield. The direct addition of exogenous glucoamylase leads to problems such as the temperature of the fermentation environment rising too quickly, seriously affecting the growth of microorganisms.

RESULTS

To solve the problem of reduced activity of glucoamylase in the late stage of solid-state fermentation of Baijiu, microcapsule beads (M-B) based on microcapsule emulsion were prepared and the effect of M-B on solid-state fermentation of Baijiu was investigated. The results showed that the release of M-B before and after drying was 53.27% and 25.77% in the liquid state (120 h) and 29.84% and 22.62% in the solid state (15 days), respectively. Adding M-B improved the alcohol by 0.33 %vol and reducing sugar content by 0.51%, reduced the residual starch content by 1.21% of the Jiupei, and had an insignificant effect on the moisture and acidity of the Jiupei.

CONCLUSION

M-B have excellent sustained-release properties. The addition of M-B in solid-state fermentation significantly increased the alcohol content, reduced the residual starch content of Jiupei, ultimately improving the starch utilization rate and liquor yield of Baijiu brewing. The preparation of M-B provides methods and approaches for applying other active substances and microorganisms in the brewing of Baijiu. © 2023 Society of Chemical Industry.

Techno-economic assessment of co-production of edible bioplastic and food supplements from Spirulina

Large amount of plastic wastes harming the environment have raised concerns worldwide on finding alternatives to non-biodegradable plastics. Microalgae has been found as a potential source for bioplastic production, besides its more common application in the pharmaceutical and nutraceutical industry. In this study, the objective was to techno-economically evaluate the large-scale co-production of Spirulina powder as food supplements and edible bioplastic for food packaging. The scale of production was large enough to satisfy 1% of local (Thailand) plastic demand (i.e., approx. 1200 MT y-1), and 1% of the global Spirulina demand (approx. 1000 MT y-1) as food supplements. Results showed that the co-production of the Spirulina powder and bioplastic revealed an attractive venture with a payback time (PBT) as low as 2.6 y and ROI as high as 38.5%. This was because the revenues generated were as high as US$ 55.6 million y-1, despite high capital (US$ 55.7 million) and operating (US$ 34.9 million y-1) costs. Sensitivity analysis showed differences in the profitability based on variations of major parameters in the study, where the split ratio of biomass used for food supplement versus bioplastic production and the bioplastic's selling price were found to be the most sensitive.

Surface Modification via Dielectric Barrier Discharge Atmospheric Cold Plasma (DBD-ACP): Improved Functional Properties of Soy Protein Film

Atmospheric cold plasma (ACP), a novel technology, has been widely adopted as an efficient approach in surface modification of the film. The effect of ACP treatment on the physicochemical and structural properties of soy protein film were investigated. As a result, the optimal conditions for the preparation of the film were determined for soy protein (10%), glycerol (2.8%), ACP treatment at 30 kV for 3 min, on the basis of elongation at the break, and water vapor permeability. Under the optimal conditions, the ACP–treated films exhibited enhanced polarity according to the increased values of solubility, swelling index, and moisture content, compared with the untreated counterpart. An increase in the hydrophilicity is also confirmed by the water contact angle analysis, which decreased from 87.9° to 77.2° after ACP pretreatment. Thermostability was also improved by ACP exposure in terms of DSC analysis. SEM images confirmed the tiny pores and cracks on the surface of film could be lessened by ACP pretreatment. Variations in the Fourier transform infrared spectroscopy indicated that some hydrophilic groups were formed by ACP pretreatment. Atomic force microscopy data revealed that the roughness of soy protein film which was pretreated by ACP was lower than that of the control group, with an Rmax value of 88.4 nm and 162.7 nm for the ACP- treated and untreated samples, respectively. The soy protein film was characterized structurally by FT–IR and DSC, and morphological characterization was done by SEM and AFM. The soy protein film modified by ACP was more stable than the control group. Hence, the great potential in improving the properties of the film enables ACP treatment to be a feasible and promising alternative to other modification methods.