Effect of cold atmospheric plasma and pulsed electromagnetic fields on strawberry quality and shelf-life

Postbiotics-enriched flaxseed mucilage coating: A solution to improving postharvest quality and shelf life of strawberry

This research aimed to assess the effects of flaxseed mucilage (Mu) coatings supplemented with postbiotics (P) obtained from Lactobacillus acidophilus LA-5 on various physical, biochemical, and microbial characteristics of strawberry fruits. Strawberry fruits were immersed for 2 min in Mu2.5 (2.5 % mucilage in distilled water), Mu5 (5 % mucilage in distilled water), P-Mu2.5 (2.5 % mucilage in undiluted postbiotics) and P-Mu5 (5 % mucilage in undiluted postbiotics) solutions and were stored at 4 °C and 85 RH for 12 days. All coatings were effective in reducing fungal count compared to the uncoated control fruits. Mu5 coating exhibited the highest efficacy, reducing fungal count by 2.85 log10 CFU/g, followed by Mu2.5 (1.47 log10 CFU/g reduction) and P-Mu2.5 groups (0.90 log10 CFU/g reduction). The fruits coated with edible coatings showed significant delays in the change of weight loss, pH, and total soluble solids as compared to the uncoated fruits. The coating containing postbiotics i.e., P-Mu5 also showed a significant increase in the total phenolic contents, total flavonoid content, antioxidant capacity, and total anthocyanin content at the end of storage relative to the uncoated fruits. Thus, Mu and P-Mu coatings may be a useful approach to maintaining the postharvest quality of strawberry fruits during cold storage.

Effect of post-harvest cold plasma treatment on physicochemical properties and inactivation of Penicillium digitatum in Persian lime fruit

Cold atmospheric plasma (CAP) treatment is used in this study to inactivate Penicillium digitatum in lime fruit at post-harvest. Limes were inoculated manually withP. digitatum spore (106 CFU/fruit) and then were treated with CAP at 30, 60, 90, and 120 s and compared with untreated samples. The results showed that increasing the exposure time of CAP reduced spores to less than 7 CFU/fruit in 120 s on the lime peel. In the treated samples, antioxidant activity had an upward trend. In addition, phenolic compounds, vitamin C, density, soluble solid content (SSC), color, and pH of the lime juice were increased (P < 0.05). Compared to the control sample, no significant changes were observed in the juice yield percentage, texture, acidity, chlorophyll, and carotenoid (P > 0.05). The best exposure for CAP treatment was 60 s since it increased phenolic compounds, antioxidant activity, and vitamin C content in the lime juice.

Intermittent high voltage electrostatic field and static magnetic field assisted modified atmosphere packaging alleviate mildew of postharvest strawberries after simulated transportation by activating the phenylpropanoid pathway

The mildew is a typical symptom of strawberries during storage. The effectiveness of intermittent high voltage electrostatic field combined with static magnetic field (HVEF-SMF) technique in inhibiting the mildew of strawberries (before and after simulation of transport vibrations) was investigated. Intermittent HVEF, SMF and HVEF-SMF treatments inhibited spoilage fungal growth on the surface of strawberries by increasing the membrane permeability and leakage of intracellular materials of spoilage fungal. The HVEF-SMF alleviated mildew in strawberries, which probably via the increase of antifungal compounds (total phenolics and lignin), phenylpropanoid biosynthetic enzyme activities (Phenylalanine ammonia-lyase, 4-coumarate-CoA ligase) and pathogenesis-related proteins enzymes activities (chitinase and β-1,3-glucanase). Overall, HVEF-SMF contributed to alleviating the mildew and disease incidence of strawberries, improving the levels of antimicrobial activity, as well as extending their shelf life from 6 d to 12 d. Therefore, HVEF-SMF treatment is a promising technology for alleviating postharvest mildew in strawberries after transportation.

Multibranched flower-like ZnO anchored on pectin/cellulose nanofiber aerogel skeleton for enhanced comprehensive antibacterial capabilities

In this study, F-ZnO NPs were used as antibacterial agents, mussel bionic dopamine exerted its adhesive action to immobilize F-ZnO NPs on the pectin/CNF aerogel skeleton. Fruit and vegetable antimicrobial mats with safety, long duration of action and high efficiency were prepared and its potential application has been investigated. The results showed that a dopamine layer was deposited on the surface of the CNF, which promoted the tight adhesion of the F-ZnO NPs to the aerogel skeleton. The F-ZnO@D-CNF aerogel exhibited a slow release of zinc ions, with the first two days being 0.40 ± 0.16 and 1.01 ± 0.13 mg/mL. The aerogel was light, can stand on the petals without collapsing, has regular and uniform pore structure, good tensile/compressive properties and high antibacterial/anti-fungal properties. Strawberries packaged with F-ZnO@D-CNF aerogel exhibited an extended shelf life of 5 days. Additionally, the strawberries maintained a soluble solid content of 6.9 ± 0.82 % and a Vc content of 44.67 ± 3.51 mg/100 g. The weight loss, color and firmness were also notably superior to the other four groups. The final concentration of zinc ions in strawberries was 3.71 ± 0.28 μg/g, which is far below the recommended dietary intake.

Edible coating enriched with cinnamon oil reduces the oxidative stress and improves the quality of strawberry fruit stored at room temperature

BACKGROUND

The present study aimed to assess the impact of a starch/gelatine coating containing cinnamon oil on selected quality attributes and redox status in strawberry fruit stored at room temperature (72 h).

RESULTS

Research showed that the application of cinnamon oil to an edible coating allows an improvement of the quality of strawberry fruit stored at room temperature. The cinnamon oil coating inhibits the development of yeast and mould, and reduces loss of soluble solids and ascorbic acid during 72 h storage at room temperature. Moreover, the coating with cinnamon oil clearly reduced the level of oxidative stress, which was manifested by a lower level of reactive oxygen species, as well as a lower activity of antioxidant enzymes. The elimination of oxidative stress in the cinnamon oil-coated fruit also contributed to lower PARP1 mRNA expression, inhibiting the metabolism of NAD⁺ and reducing ATP losses.

CONCLUSION

The coating of strawberry fruit with a starch/gelatine biofilm containing cinnamon oil is an effective method for delaying postharvest senescence of fruit and the storage degradation of tissue. © 2023 Society of Chemical Industry.

Quality characteristics of strawberry fruit following a combined treatment of laser sterilization and guava leaf-based chitosan nanoparticle coating

Background

Strawberry fruit is a rich source of antioxidants that are beneficial for human health. However, the rapid decline of strawberries dramatically reduces the shelf life and raises postharvest losses. To develop an efficient and ecological approach for maintaining the quality, strawberries (Fragaria x ananassa, cv. Festival) were treated with 0.5% chitosan coating (0.5% Ch), guava leaf-based chitosan nanoparticles coating (Gl-ChNps), and a combination treatment of 1.3 mW/cm2 laser light followed by Gl-ChNps coating (combined treatment), then stored for 12 days at 10 °C and 85–90% RH. The untreated fruit served as a control.

Results

Semi-spherical particles with an average size of 21.92 nm, a monodisperse nature, and high solution stability were formed. The findings revealed that the combined treatment completely suppressed fungal decay compared to 50% decay in control, and significantly reduced weight loss percentage to 4.68% compared to 27.35% in control. In accordance, the combined treatment had the maximum anthocyanin content and vitamin C, at 42 and 81.1 mg/100 g, respectively. The results showed that treated strawberries had less change in color, total soluble solids, titratable acidity, and pH during storage than untreated strawberries, which exhibited higher chemical changes.

Conclusions

The edible film of chitosan nanoparticles acted as a semi-permeable barrier that modified and restricted gas exchange, reduced water loss, and delayed fruit senescence. In addition, the combination of laser light with chitosan nanoparticles has been shown to control the pathogens and retain the freshness of strawberries.

Graphical Abstract

Effect of glycinebetaine on metabolite profiles of cold-stored strawberry revealed by 1H NMR-based metabolomics

Glycinebetaine (GB) has long been used as a preservative for refrigerated fruits, but the effect of GB on the global metabolites of cold-stored strawberries is still unclear. In this study, the effects of exogenous application of GB on quality-related metabolites of cold-stored strawberries were investigated by nuclear magnetic resonance (NMR)-based metabolomic analysis. The results showed that the application of GB (especially at the concentration of 10 mM) on cold-stored strawberries effectively stabilized the sugars (d-xylose and d-glucose) and amino acids (tyrosine, leucine, and tryptophan) content, and lowered the acid (acetic acid) content as well. Additionally, the GB content in strawberries also increased. This implies that the appropriate concentration of GB is a natural and safe treatment, which could maintain the quality of cold-stored strawberries by regulating levels of quality-related metabolites, and the ingestion of GB-preserved strawberries may serve as a source of methyl-donor supplementation in our daily diet.

Recent advances and future prospects of cellulose, starch, chitosan, polylactic acid and polyhydroxyalkanoates for sustainable food packaging applications

Cellulose, starch, chitosan, polylactic acid, and polyhydroxyalkanoates are seen as promising alternatives to conventional plastics in food packaging. However, the application of these biopolymers in the food packaging industry on a commercial scale is limited due to their poor performance and processing characteristics and high production cost. This review aims to provide an insight into the recent advances in research that address these limitations. Loading of nanofillers into polymer matrix could improve thermal, mechanical, and barrier properties of biopolymers. Blending of biopolymers also offers the possibility of acquiring newer materials with desired characteristics. However, nanofillers tend to agglomerate when loaded above an optimum level in the polymer matrix. This article throws light on different methods adopted by researchers to achieve uniform dispersion of nanofillers in bionanocomposites. Furthermore, different processing methods available for converting biopolymers into different packaging forms are discussed. In addition, the potential utilization of agricultural, brewery, and industrial wastes as feedstock for the production of biopolymers, and integrated biorefinery concept that not only keep the total production cost of biopolymers low but are also environment-friendly, are discussed. Finally, future research prospects in this field and the possible contribution of biopolymers to sustainable development are presented. This review will certainly be helpful to researchers working on sustainable food packaging, and companies exploring pilot projects to scale up biopolymer production for industrial applications.

Applying Cold Atmospheric Plasma to Preserve the Postharvest Qualities of Winter Jujube (Ziziphus jujuba Mill. cv. Dongzao) During Cold Storage

Winter jujube (Ziziphus jujuba Mill. cv. Dongzao) is a very popular horticultural fruit worldwide, which contains a high number of bioactive compounds. Nevertheless, jujube is perishable by microbial contamination and has a short shelf life under non-controlled conditions. Cold atmospheric plasma (CAP) presents a great potential for food sterilization, maintain postharvest quality, and prolonged storage time. Herein, this study investigated the potential effect of CAP with different exposure times (0, 5, 10, and 20 min) on the physicochemical and biochemical changes in jujube during 15-day storage at 4°C and 90% relative humidity (RH). The results showed that CAP treatment could obviously delay ripening, but displayed no effects on the speed of weight loss and moisture content. Meanwhile, the total native aerobic bacterial count in each jujube group was restrained during whole storage. However, CAP treatment showed a time-dependent manner to improve gene expression (PAL, 4CL, DFR, ANS, LAR, and ANR) related to phenolic biosynthesis. As compared to other groups, 20-min CAP treatment can keep or increase total phenolic content (TPC), maintain antioxidant activity, and reduce oxidative damage. Furthermore, the hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) content in jujube during middle storage were visibly reduced by 20-min CAP treatment. All in all, our findings concluded that appropriate CAP exposure time can be a promising candidate for the postharvest preservation of jujube.

Curcumin and its uses in active and smart food packaging applications - a comprehensive review

Active and intelligent food packaging is an innovative technology to prevent food contamination and ensure food quality and safety. Active packaging protects the food from microbial contamination, while smart or intelligent packaging enables monitoring the freshness of the food or quality change in real-time. Curcumin, one of the most well-known natural colorants, has received a lot of attention for its excellent functional properties and ability to change color with changes in pH. Curcumin, the golden component of turmeric, a spice widely used in food since ancient times, is a cost-effective and abundant biomaterial with various biological properties such as antioxidant, antibacterial, antiviral, antitumor, and anti-inflammatory. Recently, active packaging or intelligent packaging systems have been actively developed using the functional properties of curcumin. In this review, we briefly reviewed curcumin's basic biological functions and discussed comprehensive and recent progress in using curcumin in various polymer-based active and smart food packaging applications.