Effects of calcium lactate on postharvest quality of bitter gourd fruit during cold storage

Revealing the specific regulations of nitric oxide on the postharvest ripening and senescence of bitter melon fruit

Bitter melon fruit is susceptible to yellowing, softening, and rotting under room-temperature storage conditions, resulting in reduced commercial value. Nitric oxide (NO) is an important signaling molecule and plays a crucial role in regulating the fruit postharvest quality. In this study, we investigated the effects of NO treatment on changes in sensory and firmness of bitter melon fruit during postharvest storage. Moreover, transcriptomic, metabolomic, and proteomic analyses were performed to elucidate the regulatory mechanisms through which NO treatment delays the ripening and senescence of bitter melon fruit. Our results show that differentially expressed genes (DEGs) were involved in fruit texture (CSLE, β-Gal, and PME), plant hormone signal transduction (ACS, JAR4, and AUX28), and fruit flavor and aroma (SUS2, LOX, and GDH2). In addition, proteins differentially abundant were associated with fruit texture (PLY, PME, and PGA) and plant hormone signal transduction (PBL15, JAR1, and PYL9). Moreover, NO significantly increased the abundance of key enzymes involved in the phenylpropanoid biosynthetic pathway, thus enhancing the disease resistance and alleviating softening of bitter melon fruit. Finally, differential metabolites mainly included phenolic acids, terpenoids, and flavonoids. These results provide a theoretical basis for further studies on the physiological changes associated with postharvest ripening and senescence of bitter melon fruit.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42994-023-00110-y.

Enhancing phytochemical parameters in broccoli through vacuum impregnation and their prediction with comparative ANN and RSM models

Amidst increasing demand for nutritious foods, the quest for effective methods to enhance health-promoting attributes has intensified. Vacuum impregnation (VI) is a promising technique to augment produce properties while minimizing impacts on biochemical attributes. In light of broccoli's growing popularity driven by its nutritional benefits, this study explores the impact of VI using ascorbic acid and calcium chloride as impregnation agents on enhancing its phytochemical properties. Response surface methodology (RSM) was used for optimization of the vacuum impregnation process with Vacuum pressure (0.6, 0.4, 0.2 bar), vacuum time (3, 7, 11 min), restoration time (5, 10, 15 min), and concentrations (0.5, 1.0, 1.5%) as independent parameters. The influence of these process parameters on six targeted responses viz. total phenolic content (TPC), total flavonoid content (TFC), ascorbic acid content (AAC), total chlorophyll content (TCC), free radical scavenging activity (FRSA), and carotenoid content (CC) were analysed. Levenberg-Marquardt back propagated neural network (LMB-ANN) was used to model the impregnation process. Multiple response optimization of the vacuum impregnation process indicated an optimum condition of 0.2 bar vacuum pressure, 11 min of vacuum time, 12 min of restoration time, and 1.5% concentration of solution for vacuum impregnation of broccoli. The values of TPC, TFC, AAC, TCC, FRSA, and CC obtained at optimized conditions were 291.20 mg GAE/100 g, 11.29 mg QE/100 g, 350.81 mg/100 g, 1.21 mg/100 g, 79.77 mg, and 8.51 mg, respectively. The prediction models obtained through ANN was found suitable for predicting the responses with less standard errors and higher R2 value as compared to RSM models. Instrumental characterization (FTIR, XRD and SEM analysis) of untreated and treated samples were done to see the effect of impregnation on microstructural and morphological changes in broccoli. The results showed enhancement in the TPC, TFC, AAC, TCC, FRSA, and CC values of broccoli florets with impregnation. The FTIR and XRD analysis also supported the results.

Combination of calcium lactate impregnation with UV-C irradiation maintains quality and improves antioxidant capacity of fresh-cut kiwifruit slices

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Calcium lactate and shortwave ultraviolet combined treatment (abbr. CA-L + UV-C) has a synergistic effect on fresh-cut kiwifruits preservation.

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CA-L + UV-C reduced microbial growth.

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CA-L + UV-C increased phenolics accumulation by activating related enzyme activities.

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CA-L + UV-C improved antioxidant capacity by increasing antioxidant enzyme activity and promoting phenolics accumulation.

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CA-L + UV-C maintained quality by improving antioxidant capacity.

This study investigated the combined effects of calcium lactate (CA-L, 3 g L⁻¹) and shortwave ultraviolet (UV-C, 4.0 kJ m⁻²) irradiation on quality attributes and antioxidant defense capacity of fresh-cut kiwifruits at refrigerated storage for 7 d. The results indicated that CA-L and UV-C joint treatment, compared to either treatment alone, alleviated microbial load, showed higher quality on ascorbic acid (AsA), green color, total chlorophyll, flesh hardness, total sugar, total acid and malonaldehyde (MDA) content. Besides, it inhibited O2·- and •OH generation, induced H₂O₂ production, improved the activity of antioxidant enzymes (SOD, CAT and APX), activated critical enzymes (PAL, C4H and 4CL) in phenylpropanoid metabolism pathway and further enhanced total phenolic and proanthocyanidin content. Above results demonstrated that UV-C together with CA-L treatment could synergistically maintain overall quality and improve antioxidant capacity of kiwifruit slices. Therefore, the combination of CA-L and UV-C treatment showed a potential practical application in fresh-cut kiwifruits.

The Effect of Pre- and Postharvest Calcium Gluconate Treatments on Physicochemical Characteristics and Bioactive Compounds of Sweet Cherry during Cold Storage

The effects of pre- and postharvest calcium gluconate (Ca-Glu) treatments on some physicochemical characteristics and bioactive compounds of sweet cherry cv. Sweetheart during cold storage were investigated. For preharvest treatments, the Ca-Glu (1%) solution was applied to the cherry trees two times at 21 and 35 days after full bloom stage. Control trees were sprayed with distilled water at the same days. Sweet cherries, sprayed with and without Ca-Glu, were dipped into cold water (4°C) containing calcium gluconate (1%) for 30 s and only in cold water (4°C) as control, after harvest Following each treatment, cherries were placed in plastic boxes and stored at 1 ± 0.5 °C and 90 ± 5% relative humidity for 3 weeks. The weight losses of cherries increased over time but calcium (Ca) treatments, especially pre-and postharvest combination, limited these increases compared to control groups. The best result for suppressing the respiration rate of cherries was also obtained from combined treatment. Moreover, combined treatment delayed the losses of titratable acidity, fruit firmness, decay rate and sensory quality in sweet cherries during storage comparison with the pre or postharvest application of Ca-Glu alone. The effect of Ca-Clu treatments on stem chlorophyll content and antioxidant activity was not significant. Preharvest and combined treatments retarded the loss of ascorbic acid content of cherries compared to postharvest and control treatments. The total phenolic and anthocyanin content increased regularly throughout storage, regardless of treatment; however, Ca treatments delayed the accumulation of these compounds. As a result, the combined Ca-Glu treatment could be a promising method for maintaining some physicochemical characteristics and bioactive compounds in sweet cherries during cold storage.