Acción Microbiana

J. Agric. Food Chem. 2005, 53, 7807−7813

7807

Novel Edible Coating Based on Aloe vera Gel To Maintain Table Grape Quality and Safety
JUAN MIGUEL VALVERDE,† DANIEL VALERO,*,† DOMINGO MARTINEZ-ROMERO,† Ä † SALVADOR CASTILLO,† AND MARIA SERRANO‡ FABIAN GUILLEN, Ä Ä Ä
Departments of Food Technology and Applied Biology, EPSO, University Miguel Hernandez, ´ Ctra. Beniel km. 3.2, 03312 Orihuela,Alicante, Spain

A novel edible coating based on Aloe vera gel obtained according to SP Patent Filed 200302937 has been used as a means of preservation to maintain the quality and safety of cv. Crimson Seedless table grapes during cold storage and subsequent shelf life. Table grapes have a crucial economic value as a dessert fruit, but once harvested show a reduction of shelf life due to arapid loss of quality. Uncoated clusters showed a rapid deterioration with an estimated shelf life period of 7 days at 1 °C plus 4 days at 20 °C, based on the fast weight loss, color changes, accelerated softening and ripening, rachis browning, and high incidence of berry decay. On the contrary, those clusters treated with A. vera gel significantly delayed the above parameters related to postharvestquality losses, and storability could be extended up to 35 days at 1 °C. Interestingly, this edible coating was able to reduce the initial microbial counts for both mesophillic aerobic and yeast and molds, which significantly increased in uncoated berries over storage. Moreover, the sensory analyses revealed beneficial effects in terms of delaying rachis browning and dehydration and maintenance ofthe visual aspect of the berry without any detrimental effect on taste, aroma, or flavors. To the authors’ knowledge, this is the first time A. vera gel has been used as an edible coating in fruits, which would be an innovative and interesting means for commercial application and an alternative to the use of postharvest chemical treatments.
KEYWORDS: Aloe vera; ripening; firmness; color;postharvest; sensory analyses; mesophillic aerobics; yeast and molds

INTRODUCTION

Aloe Vera is a tropical and subtropical plant that has been used for centuries for its medicinal and therapeutic properties (1). The two major liquid sources of A. Vera are a yellow latex (exudate) and a clear gel (mucilage), which proceeds from the large leaf parenchymatic cells (2). The predominant medical uses ofthe orally ingested gel juice are against ulcerous, gastrointestinal, kidney, and cardiovascular problems and also to reduce the cholesterol and triglyceride levels in blood. Moreover, other properties such as antiinflammatory and antibiotic activities and activities against some diseases (diabetes, cancer, allergy, AIDS) have been reported (1, 3). However, the main use of A. Vera gel is in thecosmetic industry, including treatment of burns and scars and in wound healing (4). There are some reports on the antifungal activity of A. Vera gel against several pathogenic fungi including Botrytis cinerea (5-7). Recently, there has been increasing interest for the use of A. Vera gel in the food industry as a functional ingredient food in drinks, beverages, and ice creams (8). Nevertheless, most of* Corresponding author (fax 34-96-6749677; e-mail daniel.valero@umh.es). † Department of Food Technology. ‡ Department of Applied Biology.

the so-called Aloe products may contain very small amounts of the active compounds, because the processing techniques used to obtain A. Vera gel affect the product quality and the amount of bioactive compounds in the final product. In this sense, aprocedure of extraction and processing has been developed to ensure the biological integrity, the sensorial stability, and the quality of the final product for the food industry application (9). In Spain, our group has filed a patent for the use of A. Vera gel as an edible coating for postharvest treatment on fruits and vegetables (10). Table grapes show severe problems during postharvest storage and...