Authors Rasouli, M., Koushesh Saba, M. and Ramezanian, A.
Effects of salicylic acid (SA) and Aloe vera gel (AV) on microbial load, quality, and chilling injury of Thomson Navel oranges (Citrus sinensis L. Osbeck) stored at 4?±?1?”C and 80?±?5% RH were evaluated. Fruit was treated by immersion in distilled water (control), SA 2?mM, AV 30%, and the combination of SA?+?AV. Decay index, microbiological analysis, weight loss, firmness, soluble solids content, titratable acidity, vitamin C, total phenol, chilling injury, electrolyte leakage, malondialdehyde and sensory evaluation were measured at 0, 20, 40, 60 and 80 days of storage. Results showed that treated fruit had lower decay index, total yeasts?+?molds count, total aerobic mesophilic bacteria, weight loss and higher firmness, soluble solids content, titratable acidity, vitamin C, and total phenol content. The treatment with SA and AV gel coating reduced malondialdehyde, electrolyte leakage and chilling injury. Fruit odor attributes was not affected by treatments but skin appearance, sweetness, juiciness, and intention to buy in treated fruit were higher than control. SA?+?AV was more effective than SA and AV solely in maintaining fruit quality and reducing microbial load and chilling injury. It could be concluded that the combination of SA with AV might leads to increased oranges fruit shelf-life. Citrus fruit have major popularity all over the world due to their high nutritional value, bioactive compounds, good taste, and widespread availability. However, pathogens can cause large losses of citrus fruit during transportation and storage. Furthermore, these fruits are highly sensitive to low temperatures during storage. Low temperatures can cause the production of reactive oxygen species (ROS), cell membrane damage, and ultimately the chilling disorder. Microbial decay and chilling injury (CI) cause physiological and biochemical changes and finally lead to fruit quality decrease, nutrient losses, water losses and decay. In the past decade, resistance inducers or elicitors and coatings are considered technologies with the great potential to maintain the quality of fruit and to protect them from the influence of external abiotic and biotic stresses. The application of agents known as resistance inducers (elicitors) to biotic or abiotic stresses is a way to maintain postharvest fruit quality. Salicylic acid (SA), which considered a signaling molecule, plays an important role in regulating many physiological processes and systemic resistance. Also, SA could cause the production of defense compounds such as pathogenesis-related proteins or polyphenols. In recent years, a few studies have reported that SA increased resistance to decay of Valencia or Lanelate orange and grapefruit and delayed softening of kiwifruit, lipid peroxidation of Cara cara navel orange, and CI of lemon. Coatings act as a semi-permeable barrier which restricts the movement of gases and water vapor could reduce the rate of respiration and water loss from the fruit. Moreover, coating compounds might intrinsically have antioxidants and antimicrobial properties (Vieira et al., 2016) or be the carrier of those. In general, edible coatings are formed of polysaccharides, lipids, proteins, and or of different compositions. Aloe vera (AV) gel is one of these coatings that have been considered in recent years. The AV gel is mainly composed of polysaccharides and minerals, sugars, vitamins, antimicrobial and antioxidant agents, such as phenolic compounds. The AV gel coating in table grapes, nectarines and strawberry reduced respiration rates, moisture loss, softening, microbial decay and maintained the other quality characteristics and could extend the fruits shelf-life. There is no report regarding the combination effects of SA and AV gel coating on postharvest quality of citrus fruit. The aim of this study was to determine the effects of SA in combination with AV gel coating on microbial decay, fruit quality and CI of Thomson Navel oranges during storage.
