This study utilized zein as the core material and flaxseed gum (FG) as the coating material to prepare composite nanoparticles via the anti-solvent precipitation method. The results demonstrated that the nanoparticles prepared with 20 mg/mL zein and 0.2 mg/mL FG exhibited the best stability and uniformity, with a particle size of 81.98 nm, polydispersity index (PDI) of 0.25, and zeta potential of -37.69 mV. Fourier transform infrared spectroscopy (FTIR) analysis indicated that hydrogen bonding, electrostatic interactions, and hydrophobic interactions were the primary driving forces for zein-FG formation. X-ray diffraction (XRD) analysis revealed the presence of interactions between FG and zein. Furthermore, the incorporation of FG into zein nanoparticles enhanced its salt ion, pH, and storage stability. In conclusion, zein-FG nanoparticles show potential as novel materials for developing high-efficiency nanodelivery systems.

A comparative analysis of the preservation effects of different concentrations of chitosan hydrochloride (CHC) and chitosan (CTS) was done on fresh-cut broccoli. Furthermore, the effect of CHC on the storage quality and chlorophyll metabolism of fresh-cut broccoli was explored. The results showed that CHC provided good preservation of fresh-cut broccoli; this effect was concentration-dependent, being most pronounced at 5 g/L CHC. On the 20th day of storage, the mass loss and respiration intensity of broccoli treated with 5 g/L CHC decreased by 56.87% and 36.12% compared with the control group treated with distilled water, and by 13.44% and 1.18% compared with the 5 g/L CTS-treated group, respectively. Moreover, 5 g/L CHC treatment effectively delayed the yellowing, significantly the increase of chlorophyllase (CLH), Mg-dechelatase (MDcase), pheophytinase (PPH) and pheophyllase a oxygenase (PAO) activities, and maintained high total chlorophyll, chlorophyll a and chlorophyll b, and carotenoid contents. On the 15th day of storage, the chlorophyll content of the 5 g/L CHC treated-group was 62.13% higher than that of the control group. These findings suggest that 5 g/L CHC maintains the storage quality and delays the degradation of chlorophyll in fresh-cut broccoli, showing its potential in extending the storage period.

The effect of postharvest pre-storage temperature on the wound healing of potato minitubers grown in an aeroponic system was evaluated, and its possible mechanisms were also explored. Potato mini-tubers (cv. Tongshu 1’) free from artificial damage were pre-stored at 4, 15 or 25 ℃ (86%–88% relative humidity) in a dark environment for 20 days. Mass loss rate was measured during pre-storage, the accumulation of suberin and cork in periderm cells was observed, the degree of suberization was examined, and the changes in phenylpropane and reactive oxygen species metabolism in potato tuber periderm were also analyzed. Results showed that pre-storage at 15 ℃ significantly promoted the accumulation of suberin polyphenolics (SPP) and suberin polyaliphatics (SPA) and the degree of suberization in periderm tissue. On the fifth day of pre-storage, the accumulation of SPP and SPA and the degree of suberization in potato tubers prestored at 15 ℃ were higher than those at 4 and 25 ℃ by 50.90% and 26.94% (P < 0.05); 44.89% and 30.23% (P < 0.05); and 27.66% and 8.18%(P < 0.05), respectively. Pre-storage at 15 ℃ also significantly increased phenylalanine ammonia lyase (PAL) activity (P < 0.05), and augmented the contents of total phenols, flavonoids and lignin. On day 5, PAL activity in potato tubers prestored at 15 ℃ was 34.46% and 12.64% higher than that at 4 and 25 ℃, respectively (P < 0.05). The contents of total phenols and flavonoids were 11.93% and 40.05% higher than those at 4 ℃, and 2.72% and 15.50% higher than those at 25 ℃, respectively. On the 20^th day, the content of lignin in potato tubers prestored at 15 ℃ was 24.50% and 8.24% higher than that at 4 and 25 ℃, respectively (P < 0.05). In addition, pre-storage at 15 ℃ significantly increased the contents of H₂O₂ and superoxide anion and peroxidase (POD) activity in periderm tissue. The findings suggested that postharvest pre-storage at 15 ℃ can accelerate the wound healing of potato minitubers grown in an aeroponic system through activating phenylpropane and reactive oxygen species metabolism in periderm tissue, and increasing the accumulation of SPP and SPA and the degree of suberization.

Black spot, caused by Alternaria alternata, is one of the major postharvest diseases of pear fruit, which can cause severe economic losses. The inhibitory effect of pyridine-2,6-dipicolinic acid (DPA) produced by Bacillus subtilis on the growth of A. alternata and black spot development was studied through in vitro and in vivo tests, and its possible mechanism of action was also evaluated. Results showed that DPA significantly inhibited the colony growth, spore germination and germ tube elongation of A. alternata. The colony diameter of A. alternata treated with 2.0 mmol/L DPA was only 51.76% as compared to the control group after incubation for nine days, and A. alternata growth was completely inhibited by 4.0 mmol/L DPA treatment. DPA treatment had a significant control effect on the development of black spot on pear fruit. The lesion diameter on Zaosu pear fruit treated with 20.0 mmol/L DPA was only 55.17% as compared to the control after 11 days of storage. Furthermore, it was shown that DPA treatment significantly increased the cell membrane permeability and mycelial conductivity of A. alternata, leading to protein and nucleic acid leakage. At the same time, DPA treatment reduced the ergosterol content and increased the malondialdehyde content of A. alternata. The above results indicate that DPA has strong antifungal activity through delaying A. altenata growth, destroying membrane integrity, increasing membrane permeability and promoting membrane lipid oxidation.

We performed this study in order to evaluate the control effect and mechanism of the biosurfactant rhamnolipids (RLS) on black spot disease caused by Alternaria alternata in pear fruit. The results showed that RLS treatment at a mass concentration of 20 mg/mL effectively enhanced resistance to A. alternata, and the lesion diameter was only 64.29% of that of the control group at 12 days following the treatment. Furthermore, it was shown that compared to the control group, RLS treatment significantly increased the activities of phenylalanine ammonia lyase (PAL), cinnamate acid 4-hydroxylase (C4H), 4-coumarate coenzyme A ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD), as well as the contents of total phenols and flavonoids in pear fruit tissue. The activities of chitinase and β-1,3-glucanase were significantly induced. The activities of NADPH oxidase (NOX), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), and the contents of H₂O₂ and superoxide anion radical in the early and middle stages of storage were also increased by RLS treatment. Meanwhile, the ascorbate-glutathione (ASA-GSH) cycle was activated to maintain the dynamic balance of reactive oxygen species (ROS) production and scavenging in pear fruit tissue, and the membrane permeability and the content of malondialdehyde (MDA) were reduced. Collectively, this study suggested that post-harvest rhamnolipid treatment can enhance black spot disease resistance in pear fruit by regulating phenylpropane metabolism, ROS metabolism and pathogenesis-related proteins.

The effect of treatment with 5 g/L chitosan (CTS), 100 μmol/L melatonin (MT) and their combination on the storage quality and chlorophyll metabolism of fresh-cut broccoli (Brassica oleracea L. var. italica Planch.) during storage at (15 ± 1) ℃ and relative humidity (RH) of 85%–90% were investigated through sensory evaluation, physiological and biochemical characterization, and texture analysis. The results showed that separate and combined treatment with CTS and MT effectively maintained the sensory quality of fresh-cut broccoli, and the sensory scores of the samples treated with CTS, MT and their combination were 3.36, 2.83 and 5.17 times higher than that of the control group on the 7th day of storage, respectively. Compared with the control group, the combined treatment could significantly inhibit the activity of chlorophyll-degrading enzymes in broccoli (P < 0.05), thereby inhibiting chlorophyll degradation, while significantly reducing the rate of mass loss and respiratory intensity of fresh-cut broccoli (P < 0.05). Furthermore, it was found that the combined treatment increased chlorophyll content by 83.80%, reduced chlorophyllase (CLH), Mg-dechelatase (MDcase), pheophyllase (PPH) and pheophyllase a oxygenase (PAO) activities by 5.78%, 26.76%, 18.59% and 34.87%, respectively, and decreased mass loss rate and respiratory intensity by 24.82% and 45.28%, respectively on the 5th day of storage. Also, the combined treatment better maintained the texture properties of fresh-cut broccoli, such as hardness and chewiness, as well as the contents of soluble solids, soluble protein, total phenols and flavonoids. These findings suggest that combined treatment with CTS and MT can effectively delay the yellowing and maintain the quality of fresh-cut broccoli.

In order to develop plant essential oil microcapsules and evaluate their application in the preservation of fruits and vegetables, microcapsules were prepared by spray-drying method using p-anisaldehyde as the core material and octenyl succinic anhydride-modified starch and chitosan as the wall material, and the effect of the microcapsules on the preservation of carrots was investigated. The results showed that p-anisaldehyde was successfully encapsulated. The emulsion added with 3.5 g of p-anisaldehyde had good dispersity with an encapsulation rate of 77.21%. The formed microcapsules were spherical with a smooth surface, and the thermal stability of anisaldehyde was improved after encapsulation. Further studies showed that fumigation with anisaldehyde microcapsules effectively inhibited the respiration intensity of carrots during storage, delayed the increase in L* and the decrease in a* and b*, slowed down the decrease in soluble solids content and the increase in mass loss, and maintained textural properties such as hardness. The fumigation treatment also increased the activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in carrot tissues. In conclusion, the anisaldehyde microcapsules could effectively maintain the quality of carrots during postharvest storage.