Effect of modified atmosphere package on attributes of sweet bamboo shoots after harvest.

Tender bamboo shoots undergo rapid senescence that influences their quality and commercial value after harvest. In this study, the tender sweet bamboo shoots ('Wensun') were packed by a passive modified atmosphere packaging (PMAP) to inhibit the senescence process, taking polyethylene package as control. The increase in CO2 and the decrease in O2 gas concentrations in the headspace atmosphere of the packages were remarkably modified by PMAP treatments. The modified gas atmosphere packaging inhibited the changes in firmness, as well as the content of cellulose, total pectin, and lignin in the cell walls of bamboo shoots. The enzymatic activities of cellulase, pectinase, and polygalacturonase that act on cell wall polysaccharides, and phenylalanine ammonia lyase, cinnamyl alcohol dehydrogenase, peroxidase, and laccase regulating the lignin biosynthesis were modified by PMAP treatment different from control during storage. The expression levels of the lignin biosynthesis genes PePAL3/4, PeCAD, Pe4CL5, PeC4H, PeCCOAOMT, PeCOMT, cellulose synthase PeCESA1, and related transcription factors PeSND2, PeKNAT7, PeMYB20, PeMYB63, and PeMYB85 were clearly regulated. These results suggest that PMAP efficiently retards the changes in lignin and cell wall polysaccharides, thus delaying the senescence of tender sweet bamboo shoots during storage.

Effect of plasma-activated lactic acid on microbiota composition and quality of puffer fish (Takifugu obscurus) fillets during chilled storage.

Fresh puffer fish (Takifugu obscurus) are susceptible to microbial contamination and have a very short shelf-life of chilled storage. Hence, this study aimed to evaluate the effects of plasma-activated lactic acid (PALA) on microbiota composition and quality attributes of puffer fish fillets during chilled storage. The results showed that PALA treatment effectively reduced the growth of bacteria and attenuated changes in physicochemical indicators (total volatile basic nitrogen, pH value, K value, and biogenic amines) of puffer fish fillets. Additionally, insignificant changes were observed in lipid oxidation during the first 8 days (p > 0.05). Illumina-MiSeq high-throughput sequencing revealed that PALA effectively inhibited the growth of Pseudomonas in puffer fish fillets and maintained the diverse characteristics of the microbial community. In combination with sensory analysis, PALA extended the shelf life of puffer fish fillets for 4 days, suggesting that PALA could be considered a potential fish fillet preservation method.

Effects of modified atmosphere packaging on the postharvest quality of mulberry leaf vegetable.

Fresh mulberry leaf vegetable is nutritive and becoming popular. However, available preservation technologies are deficient. In present work, the effects of two kinds of modified atmosphere packaging on postharvest quality of fresh mulberry leaf vegetable stored at 4 °C were evaluated. The respiration rate of samples in the modified polyethylene packages (MP20) was 12.88-22.65% lower than that in normal polyethylene packaging (CK). The content of total soluble solids, soluble protein, and total polyphenol in MP20 was less changed than that in CK, and the vitamin C retention was higher as well. Moreover, the lignin content in MP20 was lower than that in CK during storage (19.79% vs 13.38% at day 8), and that was significantly positively related to the polyphenol oxidase and peroxidase activities inhibition. Taken together, a packaging with moderate gas permeability (MP20) is suitable for nutrition maintenance and lignification inhibition of fresh mulberry leaf vegetable during cold storage.

High oxygen atmospheric packaging treatment regulates the postharvest changes of Chinese kale (Brassica oleracea var. alboglabra) during storage.

Chinese kale is one of the most popular vegetables in southern China and Asia, but it has a short shelf-life. The effect of high oxygen atmospheric packaging (HOAP) treatment on the respiration rate as well as chlorophyll content and the expression of their metabolism-related genes of the soluble proteins in Chinese kale during storage were assessed. The results showed that Chinese kale subjected to HOAP treatment showed stimulated respiration rate and regulated expression of chlorophyll metabolism-related genes, such as BrChlases, BrPPH (pheophytin pheophorbide hydrolase), BrPAO (pheidea oxygenase gene), BrRCCR (red chlorophyll catabolite reductase), and BrSAG12 (senescence-associated gene), compared to the Chinese kale in the control. The activities of chlorophyll enzymes, that is, Chlase and Mg-dechelatase, were also influenced by HOAP treatment during storage. Furthermore, the total content of soluble proteins was stimulated to accumulate, and the intensity of protein bands, detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiling, increased in HOAP-treated samples. Based on the current results, as well as the results of our previous study regarding HOAP treatment of other vegetables, we speculate that HOAP may function by regulating the respiration rate and the accumulation of functional proteins, especially chlorophyll catabolic and antioxidant enzymes, to maintain the freshness of Chinese kale during storage. PRACTICAL APPLICATION: HOAP treatment could be a potential method for delaying quality changes and extending the shelf-life of Chinese kale after harvest.

Nanocomplexation between thymol and soy protein isolate and its improvements on stability and antibacterial properties of thymol.

The complexation of thymol with soy protein isolate (SPI) at various mixing mass ratios, as well as some physicochemical characteristics, stability and antibacterial properties of the resultant complexes, was evaluated. The loading capacity of thymol in complexes formed at a mixing mass ratio of 2.5:12 was 10.36%, and the particles were spherical with a z-average diameter less than 110 nm. Fluorescence spectroscopy results indicated the SPI-thymol nanocomplexes were formed mainly through hydrophobic interactions. Upon nanocomplexation, the solubility, sustained release, thermal stability and antibacterial activity of thymol were greatly improved. Moreover, the encapsulation efficiency and solubility of thymol in complexes were improved with the increasing mixing mass ratio, while the stability and antibacterial activity of thymol were not significantly different among all the complexes. These findings suggest that SPI could be used as a nanocarrier for improving solubility and stability of thymol.

Soy Soluble Polysaccharide as a Nanocarrier for Curcumin.

The complexation between soy soluble polysaccharide (SSPS) and curcumin at pH 7.0 and 4.0, as well as some physicochemical characteristics of the resultant complexes, was investigated. The encapsulation efficiency and loading amount of curcumin in the complexes at pH 4.0 reached 67.3% and 4.49 µg/mg SSPS, respectively. Ethanol-induced denaturation and structural unfolding of the protein fraction in SSPS was essential for complex formation. The complexation with curcumin resulted in aggregation of SSPS and the subsequent formation of compacted nanoparticles with curcumin as the core. The complexation greatly improved the heat stability and in vitro bioaccessibility of curcumin. In general, the encapsulation efficiency, heat stability, and bioaccessibility of curcumin in the complexes at pH 4.0 were better than those at pH 7.0. The findings are of importance for the development of food grade nanovehicles for enhanced water solubility, stability, and bioaccessibility of hydrophobic bioactives.

Core-Shell Soy Protein-Soy Polysaccharide Complex (Nano)particles as Carriers for Improved Stability and Sustained Release of Curcumin.

Using soy protein isolate (SPI) and soy-soluble polysaccharides (SSPS) as polymer matrixes, this study reported a novel process to fabricate unique core-shell complex (nano)particles to perform as carriers for curcumin (a typical poorly soluble bioactive). In the process, curcumin-SPI nanocomplexes were first formed at pH 7.0 and then coated by SSPS. At this pH, the core-shell complex was formed in a way the SPI nanoparticles might be incorporated into the interior of SSPS molecules without distinctly affecting the size and morphology of particles. The core-shell structure was distinctly changed by adjusting pH from 7.0 to 4.0. At pH 4.0, SSPS was strongly bound to the surface of highly aggregated SPI nanoparticles, and as a consequence, much larger complexes were formed. The bioaccessibility of curcumin in the SPI-curcumin complexes was unaffected by the SSPS coating. However, the core-shell complex formation greatly improved the thermal stability and controlled release properties of encapsulated curcumin. The improvement was much better at pH 4.0 than that at pH 7.0. All of the freeze-dried core-shell complex preparations exhibited good redispersion behavior. The findings provide a simple approach to fabricate food-grade delivery systems for improved water dispersion, heat stability, and even controlled release of poorly soluble bioactives.

Nanocomplexation between curcumin and soy protein isolate: influence on curcumin stability/bioaccessibility and in vitro protein digestibility.

The complexation of nanoparticles in unheated and heated (at 75-95°) soy protein isolate (SPI) with curcumin and the effects on curcumin stability/bioaccessibility and in vitro protein digestibility were investigated. The nanoparticles did not display noticeable changes in size and morphology upon nanocomplexation with curcumin, except their surface hydrophobicity. The encapsulation efficiency of curcumin progressively decreased with increasing initial curcumin concentration in the dispersion, while the load amount linearly increased. The solubility of curcumin in water was enhanced by the complexation above 98000-fold (vs free curcumin in water). The formation of the nanocomplexes considerably improved the storage stability of curcumin. In vitro simulated digestion experiments indicated that the complexation also improved the bioaccessibility of curcumin; the bioaccessibility was greatly impaired by hydrolysis-induced protein aggregation. Addtionally, the nanocomplexation significantly improved the in vitro protein digestibility of both unheated and heated SPI.

Nanocomplexation of soy protein isolate with curcumin: Influence of ultrasonic treatment.

Soy protein isolate (SPI) can act as effective nanocarriers for water-insoluble curcumin, however, the maximal capacity of this protein to load curcumin and molecular mechanism for the formation of the nanocomplexes are still little known. This work investigated the formation and properties of SPI-curcumin nanocomplexes formed at a low concentration of 0.05% (w/v), as well as the influence of a high intensity ultrasonic treatment on the nanocomplexation. Most of the particles in non- or ultrasonic-treated SPIs were present in nanoparticle form with z-average sizes of about 50-52nm. The load amount (LA) of curcumin in the non-treated nanocomplexes reached 103.9µg/mg SPI. The ultrasonic treatment of the protein solution further significantly increased the LA, while the LA was considerably decreased by the treatment after the nanocomplexation. The complexation with curcumin significantly increased the particle size and ζ-potential of both non- and ultrasonic-treated SPIs, but led to a considerable reduction in surface hydrophobicity, with the greater changes observed for ultrasonic-treated SPI. The nanocomplexation with SPIs remarkably improved the storage stability of curcumin, with much better improvement observed for the ultrasonic-treated SPI. Both the number and nature of hydrophobic sites are important for the nanoparticles in SPI to exhibit high capacity to load curcumin molecules. This study confirmed that SPI exhibited a high capacity to load water-insoluble curcumin, and an ultrasonic pretreatment could further improve its encapsulation efficiency and stability of curcumin.