Effects of Aloe vera gel coatings on shelf life of Citrus sinensis fruits stored at ambient temperature.

Authors Adetunji C. O., Fawole O.B , Afolayan S.S, OlaleyeO.O. Adetunji J.B.

Lime (Citrus aurantiifolia) is typically a round, green, citrus fruit that contains acidic juice vesicles. It is rich in vitamin C (35% of the daily value per 100 g serving) and contains citric acid at almost twice the level of grapefruit juice and about five times higher than that in orange juice. Lime pulp and peel contain diverse phytochemicals, including polyphenols and terpenes After harvest, lime fruit turns yellow and later brown, and this is associated with loss of freshness and shelf life. This can occur within 7–10 days from harvest. Extending fruit shelf life is imperative to reduce postharvest losses, minimize supply and price volatility, and increase profits at the farmgate and downstream markets. Several techniques are available to extend fruit shelf life, but techniques that pose no hazard to people and the environment are highly desirable and are gaining more emphasis in the global drive towards sustainable development. Among safe and environment friendly postharvest techniques for horticultural produce is the use of edible coatings. Aloe vera gel (AVG) coating is an edible coating technique that has received a lot of research interest as can be seen from several reviews on its use on fruits, vegetables, and fresh-cut products Aloe vera contains 110 potentially active constituents from six different classes: chromone and its glycoside derivatives; anthraquinone and its glycoside derivatives; flavonoids; phenylpropanoids and coumarins phenylpyrone and phenol derivatives; and phytosterols. As an edible coating, AVG provides a thin film on the fruit surface which acts as a barrier against atmospheric gases and moisture, thereby reducing respiration and transpiration (water loss) and delaying postharvest deterioration of produce. AVG also inhibits fruit decay due to its antimicrobial properties. Usual responses of AVG-coated fruits include reduced loss of weight, firmness, sensory and visual qualities, ascorbic acid and titratable acidity, slowed increase in total soluble solids (TSS), reduced decay and extension of shelf life. However, effective treatment and storage conditions vary: in apple, 10–20% AVG as a 5 min dip prior to cold storage; in grapes, 20% AVG as a 5 min dip before storage at 0″C or 30″C for the ‘Thompson Seedless’ variety , 67% AVG as a 5 min dip before storage at 4″C, 85±5% RH for the ‘Askari’ variety, 5–10% AVG as a 2–3 second dip before storage at 15″C for an Indian variety, and 25% AVG spray before cold storage at 0″C±1, 90–95% RH for the ‘Flame Seedless’ red variety; in jujube fruit, 33–50% AVG (v/v) before cold storage at 4″C ; in mango, 100% AVG as a 3 min dip before ambient storage for the ‘Keitt’ variety and 50–75% AVG as a 25 min dip before storage at ambient temperature (15–22″C) or at 13″C for the ‘Ngowe’ variety; in papaya, 1.5% AVG as a 5 min dip before ambient storage for the ‘Shahi’ (BARI Papaya-1) variety and 50% AVG as a 15 min dip before ambient storage (30 ± 3″C, 42–55% RH) for an unspecified variety; and in pomegranate, 100% AVG before ambient storage. Similar responses were obtained in vegetables: in tomato, 100% AVG for the ‘Ruchi 618’ variety at the breaker stage, 100% AVG as a 2 min dip for ‘Roma’ and ‘UTC’ varieties at the fully ripe stage, and 2% AVG as a 2 min dip in mature green fruits (unspecified variety) ; in the bell pepper var. ‘Yolo Wonder’, 4–6% AVG as a 5 min dip before cold storage at 8 ± 1″C, 90–95% RH; and in cucumber, 100% AVG. From these reports, there are wide differences in the effective AVG dose and treatment duration. In general, lower doses of AVG (? 25%) are effective preservatives for thin skinned produce such as grapes, nectarines, raspberries, tomatoes and sweet cherries; moderate doses (25–50%) are effective for medium-skinned products such as peppers and mangoes; and high doses (? 50%) are required for thick-skinned fresh products such as pineapples, plums and pistachios. The incorporation of ascorbic acid, glycerol or chitosan usually improves the preservative characteristics of the coatings. In citrus, studies showed that AVG coating enhanced fruit quality and shelf life despite differences in treatment conditions. In oranges (Citrus sinensis), for example, AVG (100%) coating reduced losses in weight, firmness and total soluble solids and extended shelf life during ambient storage (27 ± 2″C, 50–60% RH) used different treatment conditions and showed that oranges treated with 30% AVG coating had lower weight loss, higher firmness, soluble solids content, titratable acidity and vitamin C content, better sensory qualities, particularly juiciness, and longer shelf life than uncoated fruit during cold storage (4 ± 1″C, 80 ± 5% RH). In mandarin (Citrus reticulata L.), 60% AVG reduced losses in weight, titratable acidity, juice content and vitamin C content and slowed the increase in soluble solids content during storage at 5″C, 85% RH relative to that without coating. To our knowledge, no study has been done on the use of AVG coating in lime fruit, particularly in Thailand. Therefore, this study explored the use of AVG coating in enhancing the quality and shelf life of lime.