Cellulose nanocrystals intercalated clay biocomposite for rapid Cr(VI) removal.

The application of bentonite (Bt) as an adsorbent for heavy metals has been limited due to its hydrophobicity and insufficient surface area. Herein, we present cellulose nanocrystal (CNC) modified Bt composite (CNC@Bt) with enhanced efficiency for Cr(VI) removal. CNC@Bt exhibited an increased specific surface area and a porous structure, while maintaining the original crystal structure of Bt. This was achieved through a synergistic function of ion exchange, hydrogen bonding, electrostatic interactions, and steric hindrance. The adsorption of Cr(VI) by CNC@Bt followed the pseudo-second-order kinetic and Langmuir isotherm adsorption model. Moreover, the process was endothermic and spontaneous. At an initial Cr(VI) concentration of 20 mg/L and pH = 4.0, 10 g/L CNC@Bt achieved a removal rate of 92.7%, and the adsorption capacity was 1.85 mg/g, significantly higher than bare Bt (37.9% and 0.76 mg/g). The removal efficiency remained consistently above 80% over a wide pH range, indicating the potential practical applicability of CNC@Bt. With its fast adsorption rate, pH adaptability, and stable performance, CNC@Bt presents promising prospects for the rapid treatment of Cr-contaminated wastewater.

The Impact of Storage Temperature on the Development of Microbial Communities on the Surface of Blueberry Fruit.

Microbial contamination is one of the main reasons for the quality deterioration of postharvest blueberries during storage. In this study, we investigated the surface microbiota of blueberry fruits stored at different temperatures via high-throughput sequencing of the 16S and ITS rRNA genes. The results indicated that the α-diversity of the microbial communities in samples stored at 4 °C was much higher than that in samples stored at 25 °C. The composition of the bacterial and fungal communities on the surface of the blueberry fruits varied at different storage temperatures. Ascomycota, Basidiomycota, Anthophyta, Chlorophyta, Proteobacteria, and Cyanobacteria were the most abundant phyla in the bacterial community. Furthermore, five preservation quality indices were measured, and the influence on the α-diversity of the bacterial community was found to be significantly weaker than that of the fungal community. Based on the prediction of the bacterial flora function, the change in blueberry quality during storage was closely related to its surface microbial effect. This study provides a theoretical basis for an understanding of the microbiota on the surface of blueberry fruits to cause fruit spoilage, and the development of a targeted inhibition technology to preserve blueberry fruits under different storage and transportation environments.

Preparation of a thermosensitive nanofibre membrane for blackberry preservation.

Blackberries provide multiple health benefits. However, they deteriorate easily during harvesting, storage, and transportation (temperature-changing). Therefore, to extend their shelf-life under variable temperature conditions, a temperature-sensitive nanofibre-based material with good preservation attributes was developed, composed of polylactic acid (PLA) electrospun fibres, loaded with lemon essential oil (LEO) and covered with poly (N-isopropylacrylamide) (PNIPAAm). Compared with PLA and PLA/LEO nanofibres, PLA/LEO/PNIPAAm exhibited good mechanical properties, oxidation resistance, antibacterial ability, and controlled release of LEO. The PNIPAAm layer prevented rapid LEO release below the low critical solution temperature (32 °C). When the temperature exceeded 32 °C, the PNIPAAm layer underwent a chain-to-globule transition and accelerated LEO release (slower than PLA/LEO). The temperature-controlled release of LEO via PLA/LEO/PNIPAAm membrane prolongs its action time. Therefore, PLA/LEO/PNIPAAm effectively maintained the appearance and nutritive quality of blackberries during variable storage temperatures. Our research demonstrated that active fibre membranes have great potential applications in preserving fresh products.

Caffeic acid-grafted-chitosan/polylactic acid film packaging enhances the postharvest quality of Agaricus bisporus by regulating membrane lipid metabolism.

In this study, the film assembled by caffeic acid-grafted-chitosan/polylactic acid (CA-g-CS/PLA) was used for packaging postharvest Agaricus bisporus, and its effects on postharvest quality of Agaricus bisporus by regulating membrane lipid metabolism were investigated. The results showed that compared to traditional polyethylene packaging, the cell morphology of Agaricus bisporus packaged by CA-g-CS/PLA demonstrated a more complete structure due to its lower permeability, higher fluidity and stronger ability to maintain free water. Meanwhile, CA-g-CS/PLA packaging could effectively delay the decrease rate of unsaturation value and phospholipids of Agaricus bisporus during storage. In addition, the activities and expression levels of lipoxygenase (LOX), phospholipase C (PLC) and phospholipase D (PLD) in Agaricus bisporus packaged with CA-g-CS/PLA were inhibited, while those of glycerol-3-phosphate acyltransferase (GPAT) and sphingomyelin synthase (SMS) were promoted. Therefore, CA-g-CS/PLA packaging could enhance the postharvest quality of Agaricus bisporus by regulating membrane lipid metabolism, which has great application potential in the field of new intelligent packaging.

Identification and characterization of volatile compounds in Lentinula edodes during vacuum freeze-drying.

In this study, modified headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) and electronic nose (E-nose) were utilized to investigate the dynamic aroma changes of Lentinula edodes (L. edodes) at different stages of vacuum freeze drying (VFD). The extraction efficiency of volatile compounds from vacuum freeze-dried L. edodes was improved by optimizing five parameters of the HS-SPME. A total of 50 volatiles were identified in L. edodes from different VFD stages by GC-MS. Alcohols, aldehydes, and volatile sulfur-containing compounds (VSCs) were the main flavor constituents of fresh L. edodes, frozen L. edodes, and secondary dried L. edodes. Aldehydes, ketones, and VSCs were the main aroma groups in L. edodes after primary drying. There were 20 volatiles as key odorants with the odor activity values greater than 1, in which esters appeared only before secondary drying of L. edodes. These findings could contribute to a comprehensive insight into the formation mechanism of flavor in the VFD process of L. edodes. PRACTICAL APPLICATIONS: Lentinula edodes is the second most widely cultivated edible fungus worldwide. It is considered a valuable health food not just because of its abundance of nutrients but also because of its delicious taste. This study investigated the regularity regarding the changes of volatile compounds in L. edodes during vacuum freeze drying. The results of the present study offer valuable knowledge for the formation mechanism of volatile substances in the drying process of L. edodes, which can be beneficial to promote the development and utilization of flavor substances in L. edodes.

Storage Quality Variation of Mushrooms (Flammulina velutipes) after Cold Plasma Treatment.

Flammulina velutipes is susceptible to mechanical damage, water loss, microbial growth, and other factors that lead to postharvest deterioration, thereby shortening the storage period. The purpose of this study was to analyze the effects of cold plasma treatment on the physicochemical properties and antioxidant capacity of F. velutipes during storage at 4 °C for 21 days. Compared to the control group, cold plasma cold sterilization (CPCS) treatment (150 Hz, 95 kV for 150 s) effectively inhibited the growth and multiplication of microorganisms on the surface of F. velutipes, with no significant effect on the fresh weight change and the superoxide anion generation rate, but with a higher postharvest 1,1-dephenyl-2-picrylhydrzyl (DPPH) clearance rate. Moreover, CPCS increased antioxidant enzyme activities, delayed both malondialdehyde (MDA) accumulation and vitamin C loss, inhibited the browning reaction and polyphenol oxidases (PPO) activity and protected F. velutipes cell membrane from disruption. In general, CPCS not only achieved bacteriostatic effects on F. velutipes during storage, but also reduced cell damage from free radical oxidation, resulting in better postharvest quality and longer shelf life.

Microflora and umami alterations of different packaging material preserved mushroom (Flammulina filiformis) during cold storage.

In order to clarify the effect of nanocomposite-based packaging (NP) on umami and microflora characteristics of F. filiformis during cold storage, the contents of umami amino acids and 5'-nucleotides, equivalent umami concentration (EUC), and microflora succession were investigated. Results showed that NP could delay the degradation of umami components and inhibit bacterial growth in F. filiformis. At the initial stage, the dominant bacteria were Lactobacillus, Thermus and Acinetobacter. After 15 days of storage, the bacteria count in NP reached 7.63 lg cfu/g, which was significantly (P < 0.05) lower than that in control, and the major bacterial communities of packaged F. filiformis were Ewingella, Serratia and Pseudomonas. Moreover, the correlation analysis showed that Lactobacillus, Brevibacillus and Okibacterium were negatively correlated with AMP and IMP 5-nucleotides. Present work suggested that NP could enhance the umami flavor formation and improve the microbial community structure of F. filiformis, resulting in a better commercial quality. The results provided theoretical basis for large-scale applications of NP.

Analysis of umami taste substances of morel mushroom (Morchella sextelata) hydrolysates derived from different enzymatic systems.

Seven enzyme groups were applied to hydrolyze broken fruiting bodies of morel mushroom (Morchella sextelata) to extract umami substances. Physical-chemical properties, as well as compositions and concentrations of quintessential umami compounds of morel hydrolysates were analyzed. Electronic tongue and electronic nose were used to evaluate the sensory characteristics. The results suggested that peptides below 3 kDa showed the highest correlation with umami taste. Morel hydrolysate obtained from Neutrase-Flavourzyme (NF) combination contained the most contents of small peptides (<3 kDa), free amino acids (224.83 ± 0.87 mg/g), as well as flavor 5'-nucleotides (4.84 ± 0.32 mg/g), giving the best overall flavor properties. The reaction conditions of NF were optimized by response surface methodology (RSM). The highest degree of hydrolysis (DH) was up to 36.64%. An enzymatic hydrolysis approach was established to develop novel flavor products with high umami and low bitter taste from morel mushroom.

Production of an innovative mixed Qu (fermentation starter) for waxy maize brewing and comparison of the quality of different waxy maize wines.

BACKGROUND: Waxy maize (Zea mays L. sinensis Kulesh) is a good material for brewing. Waxy maize wine, a kind of Chinese rice wine, is strongly affected by a fermentation starter named Qu. In this study, an innovative mixed Qu, consisting of two yeasts and three molds, was produced and the raw-starch brewing method was applied in winemaking. Three other waxy maize wines fermented by three kinds of commercial Qu were also analyzed for comparison. RESULTS: Due to superb growth and fermentation characteristics, Saccharomyces cerevisiae CICC1009 and Pichia anomala CICC1851 were chosen to produce yeast Qu. The addition amount of yeast Qu was determined to be 30 g kg-1 . In terms of chemical properties, mixed Qu was more suitable for making maize wine by the raw-starch brewing method than the three kinds of commercial Qu with which it was compared. The most influential components for the overall aroma profile in maize wines fermented by mixed Qu and Mifeng Qu were ethyl butyrate and ß-damascenone, respectively, while in maize wines fermented by Angel Qu and Like Qu the most influential component was ethyl octanoate. Obvious differences were found among four maize wines regarding bitterness, umami, richness, saltiness, and sourness by the electronic tongue. The olfactory characteristics of maize wine fermented by Mifeng Qu were quite different from the other three according to the electronic nose. CONCLUSION: The innovative mixed Qu can be considered as an excellent starter for raw-starch brewing of waxy maize. The chemical indices and volatile flavor compounds of waxy maize wines were greatly affected by different kinds of Qu. © 2020 Society of Chemical Industry.

Effects of pre-cutting treatments and combination drying with different orders on drying characteristics and physicochemical properties of Lentinula edodes.

BACKGROUND: Combination drying is recognized as an energy-efficient method utilized for dry product processing, and proper order of combination is a critical factor determining the effectiveness of the technique. In this study, hot air drying (HD), vacuum freeze-drying (VFD), and combination drying with different orders (HD-VFD and VFD-HD) are performed on whole Lentinula edodes and pre-cut (half-cut and quarter-cut) L. edodes. The effects of various cutting and drying approaches on drying characteristics, physicochemical properties, and microstructures of dried L. edodes were investigated. RESULTS: The longest processing time required to dry the whole L. edodes by VFD was 25 h. In contrast, the pre-cutting treatment and combination drying certainly shortened the drying time. Compared with HD, use of VFD-HD and VFD significantly decreased the shrinkage ratio, hardness, and discoloration of dried products but increased the rehydration capacity, nutrient retention, and porous microstructure. Interestingly, switching the order of combination drying provoked entirely different drying effects. Specifically, HD-VFD triggered negative effects on the shrinkage and color of dried mushrooms, and its appearance color was similar to HD-treated samples. Moreover, pre-cutting dramatically enhanced the protein content of HD-treated mushrooms, and the quarter-cut samples obtained the highest level (21.69 g kg-1 dry basis) among the three types of cutting. CONCLUSIONS: The dried L. edodes processed through pre-cutting and combination drying (VFD-HD) have optimal industrial quality, accompanied by shorter processing time. © 2020 Society of Chemical Industry.

Nanocomposite packaging regulates extracellular ATP and programed cell death in edible mushroom (Flammulina velutipes).

Our previous study indicated that nanocomposite packaging material (Nano-PM) containing nano-Ag, nano-TiO2, nano-SiO2 and nanoattapulgite alleviated postharvest senescence of Flammulina velutipes by regulating respiration and energy metabolism. In this study, extracellular ATP (eATP) and programmed cell death (PCD) were employed as critical factors to further investigate the senescence mechanism of postharvest F. velutipes. Results demonstrated that Nano-PM delayed apyrase activity decrease and stimulated critical oxidative phosphorylation-related gene expression to inhibit eATP content increase, which is a crucial signaling molecule related to delaying senescence. The regulation of eATP resulted in alleviating PCD including chromosomal concentration, DNA fragmentation, Ca2+ influx, high caspase-1 activity and cytochrome c content and leading to high cell viability. Overall, Nano-PM alleviated PCD and postharvest senescence of F. velutipes by regulating extracellular ATP.

The antioxidant and antimicrobial activities of different phenolic acids grafted onto chitosan.

Four phenolic acid-grafted-chitosan conjugates were prepared with different phenolic acids including gallic acid (GLA), caffeic acid (CA), gentisate acid (GTA) and sinapic acid (SA), and their characteristics were analyzed. Furthermore, the antioxidant and antimicrobial activities of conjugates were compared to screen out the optimal conjugates. The characterization analysis showed that the UV absorption peaks of CA-g-CS were stronger than that of GLA-g-CS, indicating a higher substitution degree. In addition, the substitution degree and antioxidant activity of caffeic acid-grafted-chitosan (CA-g-CS) and gallic acid-grafted-chitosan (GLA-g-CS) had significantly (p < 0.05) higher than CS and other two conjugates. However, CA-g-CS demonstrated stronger bacteriostatic ability, of which the minimum inhibitory concentrations (MICs) against Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis and Staphylococcus aureus were lower, and the inhibitory zones were larger than GLA-g-CS. In summary, the present findings will provide a theoretical basis for the expanding of CS application in food processing and preservation.

Effects of ultrasound-assisted extraction on antioxidant activity and bidirectional immunomodulatory activity of Flammulina velutipes polysaccharide.

In order to investigate the impacts of ultrasound-assisted extraction (UAE) on Flammulina velutipes polysaccharides (FVPs), the differences between FVPs extracted by ultrasound-assisted extraction (FVPU) and FVPs extracted by hot water extraction (FVPH) were compared in terms of yield, primary compositions, surface microstructure, helix-coil transition structure, molecular weight distribution, antioxidant activity, and bidirectional immunomodulatory activity. Results indicated that UAE changed the above properties of FVPs. Compared with FVPH, higher yield, protein content, and uronic acid content but lower polysaccharide and polyphenol contents were observed in FVPU. UAE changed the surface microstructure, destroyed the triple helix structure, and increased the proportion of low molecular weight polysaccharide components of FVPU. Compared with FVPH, FVPU showed a stronger reducing power and scavenging activities on DPPH radical, hydroxyl radical, and superoxide anion radical. FVPU was a better inhibitor of inflammation compared with FVPH. However, FVPH had a better immunity enhancing effect compared with FVPU. These results were attributed to the cavitation effect of ultrasonic waves on the structure of polysaccharides during the extraction process of UAE. These findings suggested that UAE was an efficient and environmentally friendly method to produce new polysaccharides from F. velutipes for the development of functional foods or nutraceuticals.

Effect of nanocomposite packaging on postharvest senescence of Flammulina velutipes.

A polyethylene based packaging material containing nano-Ag, nano-TiO2, nano-SiO2, and attapulgite has been prepared. The effect of nanocomposite packaging material (Nano-PM) on the senescence of Flammulina velutipes during 15 days of postharvest storage at 4 °C and a relative humidity of 90% were analyzed. The results showed that compared with normal packaging material (Normal-PM) and no packaging (No-PM), Nano-PM improved the appearance quality, reduced weight loss and cap opening. The degree of maturity and increase in molecular weight of F. velutipes polysaccharides (FVP) were delayed. The content loss of proteoglycan protein was less and degree of oxidation was lower. The storage with Nano-PM reduced the fibrosis of texture, cellulase activity, the accumulation of hydrogen peroxide (H2O2) and superoxide radical (O2-) by 18.9%, 48.3%, 26.6% and 27.8%, respectively (P < .05). The Nano-PM effectively delayed the postharvest senescence of F. velutipes, hence prolonged its shelf life and increased its preservation quality.

Proteomic Investigation of Metabolic Changes of Mushroom (Flammulina velutipes) Packaged with Nanocomposite Material during Cold Storage.

Metabolic changes of mushroom (Flammulina velutipes) applied with polyethylene (PE) material (Normal-PM) or nanocomposite reinforced PE packaging material (Nano-PM) were monitored using tandem mass tags (TMT) labeling combined with two-dimensional liquid chromatography-tandem mass spectrometry (2D LC-MS/MS) technique. A total of 429 proteins were investigated as differentially expressed proteins (DEPs) among treatments after a cold storage period. A total of 232 DEPs were up-regulated and 65 DEPs were down-regulated in Nano-PM packed F. velutipes compared to that of Normal-PM. The up-regulated DEPs were mainly involved in amino acid synthesis and metabolism, signal transduction, and response to stress while the down-regulated DEPs were largely located in mitochondrion and participated in carbohydrate metabolic, amino acid synthesis and metabolism, and organic acid metabolic. It was also revealed that Nano-PM could inhibit the carbohydrate and energy metabolism bioprocess, promote amino acids biosynthesis, enhance antioxidant system, and improve its resistance to stress, resulting in a further extended shelf life of F. velutipes.