Limiting the deterioration of mango fruit during storage at room temperature by oxalate treatment

Research Progress on Mango Post-Harvest Ripening Physiology and the Regulatory Technologies

Mango (Mangifera indica L.) is an important tropical fruit with a delicate taste, pleasant aroma, and high nutritional value. In recent years, with the promotion of the rural revitalization strategy and the development of the poverty alleviation industry, China has gradually become an important mango producer. However, the short shelf life of mango fruit, the difficulty in regulating the postharvest quality, and the lack of preservation technology are the main problems that need to be solved in China's mango industry. In this paper, the physiological changes and mechanisms of mango during postharvest ripening were summarized, including sugar and acid changes, pigment synthesis and accumulation, and aroma formation and accumulation. The physical, chemical, and biological technologies (such as endogenous phytohormones, temperature, light, chemical preservatives, and edible coatings) commonly used in the regulation of mango postharvest ripening and their action principles were emphatically expounded. The shortcomings of the existing mango postharvest ripening regulation technology and physiological mechanism research were analyzed in order to provide a reference for the industrial application and development of mango postharvest.

Melatonin treatment maintains the quality of cherry tomato by regulating endogenous melatonin and ascorbate-glutathione cycle during room temperature

Changes in quality attributes, ascorbate-glutathione (AsA-GSH) cycle, and melatonin (MLT) synthesis were evaluated in cherry tomato fruit treated with MLT solution at 0.1 mM during storage at room temperature for 16 days. According to the results, the MLT treatment was beneficial to maintaining fruit quality as indicated by the declines in weight loss, fruit decay, and titratable acid (TA), accompanied by the maintenance of fruit firmness, total soluble solids (TSS) as well as TSS/TA ratio. Also, the MLT treatment not only effectively inhibited oxidative damage via reducing relative electrolyte leakage and malondialdehyde content, but also improved antioxidant capacity via stimulating AsA-GSH cycle. Moreover, the MLT treatment promoted endogenous MLT synthesis by upregulating the expressions of biosynthetic genes consisting of SlTDC, SlT5H, SlSNAT, and SlASMLT. Thus, our results suggested that the MLT treatment might be involved in maintaining quality in cherry tomato fruit during room temperature by promoting antioxidant capacity and enhancing endogenous MLT. PRACTICAL APPLICATIONS: As a typical climacteric fruit, cherry tomato fruit ripen rapidly and are easily infected by various pathogenic fungi during storage under ambient conditions, which leads to short storage life and a decrease in economic value. The results showed that the application of MLT maintained cherry tomato quality via improving antioxidant capacities and enhancing endogenous MLT. Therefore, MLT treatment could become a promising postharvest strategy for quality maintenance in cherry tomatoes during room storage.

Thin layer drying kinetics and quality dynamics of persimmon (Diospyros kaki) treated with preservatives and solar dried under different temperatures

Poor postharvest handling, microbial infestation, and high respiration rate are some the factors are responsible for poor storage life of perishable commodities. Therefore, effective preservation of these commodities is needed to lower the damages and extend shelf life. Preservation is regarded as the action taken to maintain desired properties of a perishable commodity as long as possible. Persimmon (Diospyros kaki) is perishable fruit with high nutritive value; however, has very short shelf-life. Therefore, effective preservation and drying is needed to extend its storage life. Drying temperature and preservatives significantly influence the quality of perishable vegetables and fruits during drying. The current study investigated the effect of different temperatures and preservatives on drying kinetics and organoleptic quality attributes of persimmon. Persimmon fruits were treated with preservatives (25% honey, 25% aloe vera, 2% sodium benzoate, 1% potassium metabisulfite, and 2% citric acid solutions) under different drying temperatures (40, 45, and 50°C). All observed parameters were significantly affected by individual effects of temperatures and preservatives, except ash contents. Similarly, interactive effects were significant for all parameters except total soluble sugars, ash contents, and vitamin C. Generally, fruits treated with citric acid and dried under 50°C had 8.2% moisture loss hour^-1, 14.9 drying hours, 0.030 g H₂O g^-1 hr^-1, 1.23° Brix of total soluble solids, 6.71 pH, 1.35% acidity, and 6.3 mg vitamin C. These values were better than the rest of the preservatives and drying temperatures used in the study. Therefore, treating fruits with citric acid and drying at 50°C was found a promising technique to extend storage life of persimmon fruits. It is recommended that persimmon fruits dried at 50°C and preserved in citric acid can be used for longer storage period.

Influence of Nano-Silica/Chitosan Film Coating on the Quality of ‘Tommy Atkins’ Mango

In this study, we assessed the coating of ‘Tommy Atkins’ mangoes with films containing chitosan and nano-silicon dioxide in terms of the effects on fruit parameters as an indicator of quality. After coating, the fruits were first stored at 13 ± 1 °C and 90–95% RH for 30 days, and then at 20 ± 2 °C and 70–75% RH for 5 days, which corresponds to the marketing period. The results showed that coating treatments significantly decreased the fruits’ weight loss and decay percentage compared to the uncoated control samples over the storage period. Additionally, all coated treatments delayed skin degreening, reduced endogenous ethylene production, suppressed respiration rate, and maintained the firmness, compared to untreated control fruit. Titratable acidity and vitamin C significantly decreased in all samples during storage, but this decrease was less pronounced in the coated fruits. Furthermore, coating can delay the increments in total soluble solids and total sugars while maintaining total phenolics, and high antioxidant content of fruits, thereby extending the effective length of the marketing period of treated fruits compared to the control. It was shown that the coating combination of 2% chitosan plus 1% nano-silicon dioxide was the most successful in maintaining the mango’s quality under cold storage and during marketing.

Salicylic acid and oxalic acid in enhancing the quality and extending the shelf life of grape cv. Thompson seedless

Postharvest life of table grapes is usually shortened by berry softening, berry drop, stem browning, fungal decay. Salicylic acid reduces fruit respiration and ethylene biosynthesis, during storage of fruits. Similarly, application of oxalic acid is a secure and hopeful postharvest handling technology for keeping quality and prolonging storage life of fruit. To study the effect of Salicylic acid and oxalic acid in enhancing the quality and extending the shelf life of grape, the present investigation was conducted. The grape berries were treated with Oxalic acid (OA) (1, 2, 3, 4, and 5 mM) and Salicylic acid (SA) (0.5, 1, 1.5 and 2 mM). The treatments were compared within 16th days at an interval of 4 days. Among the treatments, SA (2 mM) showed superiority in different quality attributing characters like physiological loss in weight (PLW), berry firmness, rachis browning, berry appearance, fungal decay, berry shattering, TSS, ascorbic acid, titratable acidity, total sugars, reducing sugars, TSS: acid ratio, taste, overall acceptability and shelf life. Hence, SA (2 mM) can be used as an effective strategy for maintaining quality of table grapes.

β-Aminobutyric Acid Priming Acquisition and Defense Response of Mango Fruit to Colletotrichum gloeosporioides Infection Based on Quantitative Proteomics

β-aminobutyric acid (BABA) is a new environmentally friendly agent to induce disease resistance by priming of defense in plants. However, molecular mechanisms underlying BABA-induced priming defense are not fully understood. Here, comprehensive analysis of priming mechanism of BABA-induced resistance was investigated based on mango-Colletotrichum gloeosporioides interaction system using iTRAQ-based proteome approach. Results showed that BABA treatments effectively inhibited the expansion of anthracnose caused by C. gleosporioides in mango fruit. Proteomic results revealed that stronger response to pathogen in BABA-primed mango fruit after C. gleosporioides inoculation might be attributed to differentially accumulated proteins involved in secondary metabolism, defense signaling and response, transcriptional regulation, protein post-translational modification, etc. Additionally, we testified the involvement of non-specific lipid-transfer protein (nsLTP) in the priming acquisition at early priming stage and memory in BABA-primed mango fruit. Meanwhile, spring effect was found in the primed mango fruit, indicated by inhibition of defense-related proteins at priming phase but stronger activation of defense response when exposure to pathogen compared with non-primed fruit. As an energy-saving strategy, BABA-induced priming might also alter sugar metabolism to provide more backbone for secondary metabolites biosynthesis. In sum, this study provided new clues to elucidate the mechanism of BABA-induced priming defense in harvested fruit.

Forced Air Precooling Enhanced Storage Quality by Activating the Antioxidant System of Mango Fruits

Effects of forced air precooling on storage quality and physiological metabolism of mangoes were evaluated in this study. Mango fruits were forced air precooled for 30 min at 0°C and then stored at 13°C. Control fruits were stored at 13°C directly. Results showed that forced air precooling treatment maintained fruit firmness, inhibited fruit peel coloration, retarded hydrolysis of polysaccharide to soluble sugar, and decreased fruit decay during storage. Biochemical studies revealed that precooling treatment could eliminate reactive oxygen species (ROS) effects by enhancing related antioxidant enzyme activities, such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione reductase (GR), and polyphenoloxidase (PPO). They all contributed to the delay of mango fruit ripening and senescence in storage. These results indicate that forced air precooling treatment could maintain mango fruit quality by enhancing antioxidant activity and delaying fruit ripening.

Pre-harvest Foliar Application of Oxalic Acid Improves Strawberry Plant Growth and Fruit Quality

Delicate fruit of strawberry is susceptible to high temperature stress and fungal infection. An extensive spray program is usually adapted to secure yield and fruit quality which sometimes pose a serious threat to consumer health. However, development of eco-friendly, economical and safer strategies has always been in focus of R&D sector. In this study, field-grown strawberry plants cv. Chandler were sprayed with 1, 2 or 3 mM oxalic acid at flowering stage. Interestingly, foliar application of oxalic acid in low doses (1 mM and 2 mM) had more growth-promoting effect on strawberries whereas foliar application of 3 mM oxalic acid either negatively affected or remained ineffective. Low-dose applications of oxalic acid resulted in enhanced nitrogen (1.5-fold), phosphorus (2.5-fold) and potassium (1.75-fold) levels in leaf petioles. Increase in primary macronutrients was also correlated well with enhancement in plant growth indicators including dry biomass (1.5-fold), leaf area (1.7-fold), specific leaf area (2.8-fold) and leaf area ratio (2.6-fold), root weight ratio (1.9-fold), root-to-shoot ratio (1.4-fold). Only, leaf chlorophyll and fresh fruit weight were negatively impacted by oxalic acid. In addition to increase in number of fruits per plant, oxalic acid also improved sensory properties of strawberry fruits mainly due to increase in sugar: acid ratio (1.6-fold), ascorbic acid contents (1.2-fold) and non-reducing sugars (2-fold). Overall, foliar application of 1 mM oxalic acid favoured vegetative growth and enhanced yield and fruit quality of strawberry cv. Chandler.

Preharvest application of oxalic acid increased fruit size, bioactive compounds, and antioxidant capacity in sweet cherry cultivars (Prunus avium L.)

Trees of 'Sweet Heart' and 'Sweet Late' sweet cherry cultivars (Prunus avium L.) were treated with oxalic acid (OA) at 0.5, 1.0, and 2.0 mM at 98, 112, and 126 days after full blossom. Results showed that all treatments increased fruit size at harvest, manifested by higher fruit volume and weight in cherries from treated trees than from controls, the higher effect being found with 2.0 mM OA (18 and 30% higher weight for 'Sweet Heart' and 'Sweet Late', respectively). Other quality parameters, such as color and firmness, were also increased by OA treatments, although no significant differences were found in total soluble solids or total acidity, showing that OA treatments did not affect the on-tree ripening process of sweet cherry. However, the increases in total anthocyanins, total phenolics, and antioxidant activity associated with the ripening process were higher in treated than in control cherries, leading to fruit with high bioactive compounds and antioxidant potential at commercial harvest (≅45% more anthocyanins and ≅20% more total phenolics). In addition, individual anthocyanins, flavonols, and chlorogenic acid derivatives were also increased by OA treatment. Thus, OA preharvest treatments could be an efficient and natural way to increase the quality and functional properties of sweet cherries.

Oxalic acid alleviates chilling injury in peach fruit by regulating energy metabolism and fatty acid contents

The effects of postharvest oxalic acid (OA) treatment on chilling injury, energy metabolism and membrane fatty acid content in 'Baifeng' peach fruit stored at 0°C were investigated. Internal browning was significantly reduced by OA treatment in peaches. OA treatment markedly inhibited the increase of ion leakage and the accumulation of malondialdehyde. Meanwhile, OA significantly increased the contents of adenosine triphosphate and energy charge in peach fruit. Enzyme activities of energy metabolism including H(+)-adenosine triphosphatase, Ca(2+)-adenosine triphosphatase, succinic dehydrogenase and cytochrome C oxidase were markedly enhanced by OA treatment. The ratio of unsaturated/saturated fatty acid in OA-treated fruit was significantly higher than that in control fruit. These results suggest that the alleviation in chilling injury by OA may be due to enhanced enzyme activities related to energy metabolism and higher levels of energy status and unsaturated/saturated fatty acid ratio.