Aloe vera and ascorbic acid coatings maintain postharvest quality and reduce microbial load of strawberry fruit

Highlights

• A. vera (AV) and ascorbic acid (AA) have a synergistic effect on microbial control.

• AV and AA combination preserve strawberry bioactive constituent and fruit quality.

• AV + AA, specially higher AA concentrations, effectively delayed strawberry ripening.

Abstract

Rapid loss of quality and decay causes economic loss of strawberries after harvest. The effects of an edible coating based on natural Aloe vera (AV) gel in combination with ascorbic acid (AA; 0, 1, 3 and 5% (w/v)) on postharvest quality of strawberries was studied. After treatment, fruit weight loss, firmness, titratable acidity, soluble solids content (SSC), pH value, concentrations of ascorbic acid, anthocyanin and total phenolics, total antioxidant activity, and microbial activity were evaluated at 0, 3, 6, 9, 12, 15 and 18 days of storage (1 °C, 95% relative humidity). Compared with untreated fruit, AV + AA treatments delayed weight loss, had higher SSC, vitamin C concentrations and titratable acidity. The coatings reduced total aerobic mesophilic, yeasts and molds populations. AV + 5% AA was the most effective in delaying changes in the ripening and reducing microbial populations among the treatments. These results demonstrate that AV and AA coatings have potential to maintain postharvest fruit quality of strawberry fruit.

Introduction

Strawberries (Fragaria X ananassa Duch.), one of the most popular summer fruit worldwide, are characterized by unique and highly desirable taste and flavor, and are rich in polyphenols and anthocyanin, vitamins and amino acids (Campaniello et al., 2008). However, the fruit are highly perishable resulting in a short post-harvest life due to mechanical injury, physiological deterioration, water loss, fungal decay and high respiration rate (Perkin-Veazie, 1995, Vargas et al., 2006). Cold temperatures and modified atmospheres increase the storage life of fruit (Martinez-Romero et al., 2003), but additional methods of maintaining quality are still under investigation.

Recently, applications of edible coatings have been shown to be promising as a tool to improve the quality and extend storage and shelf life of various fruit such as papaya (Tapia et al., 2008) and strawberries (Vargas et al., 2006). Coatings can act as moisture and gas semi-permeable barriers, resulting in control of microbial growth, preservation of color and texture (Bourtoom, 2008). One such product is Aloe vera (AV), a novel edible coating for fruit storage (Serrano et al., 2006, Valverde et al., 2005). AV has antifungal activity against several pathogenic fungi including Botrytis cinerea (De Rodrıguez et al., 2005). AV coatings modify the internal gas atmosphere, reduce moisture loss, softening, respiration rates, delay oxidative browning and reduce microorganism proliferation in fruit such as sweet cherries, table grapes, nectarines and papaya (Ahmed et al., 2009, Marpudi et al., 2011, Martínez-Romero et al., 2006, Valverde et al., 2005). AV coating alone or in combination with shellac, preserves physico-chemical parameters such as color and firmness in apple slices (Chauhan et al., 2011).

Ascorbic acid (AA) and its derivatives have been used in numerous studies in fruit in concentrations ranging from 0.5 to 4% (w/v). Anti-browning effects of AA have been demonstrated in several fruit fresh-cut products under a wide range of conditions (Gil et al., 1998, Tapia et al., 2008). In addition, AA as an antioxidant that reduces vitamin C lost can be added to the edible coating material. Some studies (Tajkarimi and Ibrahim, 2011) have suggested that AA in combination with lactic acid has antimicrobial effects against Listeria monocytogenes and on Escherichia coli O157:H7 in carrot juice. Antimicrobial effects of AA on fresh cut fruit such as jackfruit (Acedo et al., 2012), apple (Perez-Gago et al., 2006, Qi et al., 2011) and papaya (Tapia et al., 2008) have been reported.

The objective of this study was to evaluate the use of AV as an edible coating for strawberries in combination with AA on quality and microbial characteristic of fresh strawberry fruit during storage.