Jawadul Misir*
Department of Food Engineering and Tea Technology, Shahjalal University of Science and Technology. Sylhet, Bangladesh
Fatema H. Brishti
Department of Food Engineering and Tea Technology, Shahjalal University of Science and Technology. Sylhet, Bangladesh
M. M. Hoque
Department of Food Engineering and Tea Technology, Shahjalal University of Science and Technology. Sylhet, Bangladesh
Aloe vera gel, Edible coating, Fruits, Postharvest life, Shelf life
Development of Host and Medicinal Plants
2. Aloe Vera The word Aloe derived from the word Arabic “Alloeh” or the Hebrew “Halal” meaning “bitter, shinny substance”. Aloe vera is known as “plant of immortality” by the Egyptians due to its beneficial effect on human health. It is generally presumed that the origin is Arabia, Somalia, Sudan, and Oman. At present, Aloe vera is widely distributed throughout the tropics and subtropics. Aloe vera is a perennial plant. It’s thick, thorn- edged leaves, ranging in color from gray to bright green, give aloe vera the appearance of a cactus, but, it is, in fact, a member of the lily family (Liliaceae). A typical Aloe vera plant produces two or three yellow tubular flowers, shaped much like those of the Easter Lily, and it flowers intermittently throughout the year. It’s thick leaves contain the water supply of the plant to survive long periods of drought. The leaves have a high capacity of retaining water also in very warm dry climates and therefore this plant can survive very harsh circumstances where most other vegetation disappears. There are two distinct layers of Aloe vera leaves which are clearly visible in transverse section: the green outer leaf rind and the soft, colorless, inner gel parenchyma. Aloe vera is an unique plant which is a rich source of many chemical compounds. Prof. Tom D. Rowe was probably first to take vital steps in the chemical analysis of the plant. Aloe vera now reported to contain as many as 75 nutrients and 200 active compounds including sugar, anthraquinones, saponins, vitamins, enzymes, minerals, lignin, salicylic acid and amino acids. In today’s society many people have food allergies or personal preferences that would prevent them from ingesting these items. Therefore, Aloe vera is a great dietary source to meet those amino acids needs. 5. Antimicrobial Activity of Aloe Vera Gel An antimicrobial is a substance that kills or inhibits the growth of microbes such as bacteria (antibacterial activity), fungi (antifungal activity), viruses (antiviral activity), or parasites (anti-parasitic activity). Reference found that A. vera gel has inhibited the growth of both gram positive and gram negative bacteria. Aloe gel composed of a wide range of constituents which are mainly responsible for this antimicrobial activity against various microorganisms. Anthraquinones presented antimicrobial activity against Staphylococcus aureus strains and against Escherichia coli, through inhibition of solute transport in membranes. Emodine has been reported to be effective against several gram positive bacteria (Cock, 2008). There are some reports on the antifungal activity of Aloe vera gel against several fungi including Colletotrichum sp. According to reference, Aloe vera gel showed good antibacterial activity against some food borne pathogenic microorganisms such as Bacillus cereus, Salmonella typhimurium, Escherichia coli, Klebsialla pneumonia etc. 7. Effect of Aloe Vera Gel Coating on Physico-chemical Properties of Fruit 7.1. Weight Loss Weight loss mainly occurs due to water loss by transpiration and loss of carbon reserves due to respiration. The rate at which water is lost depends on the water pressure gradient between the fruit tissue and the surrounding atmosphere. Aloe gel based edible coating act as barrier, thereby restricting water transfer and protecting fruit skin from mechanical injuries. Aloe vera gel (100%) has been used to preserve papaya fruit at room temperature 25°C-29°C and 82-84% RH. All samples demonstrated a gradual loss of weight during storage. Throughout storage, the weight loss of uncoated fruit (sample) was significantly greater than that of Aloe gel coated fruit. At the end of the storage, uncoated papaya showed 22.5 % loss in weight, whereas the weight losses of samples coated with Aloe vera gel was 7.93%. An experiment has also been carried out to maintain quality and safety of table grapes by coating with Aloe vera gel in cold storage (1°C, 95%). Weight loss increased during cold storage and it was significantly greater in control (uncoated fruits) than in Aloe-coated grapes. At the end of cold storage, control fruits lost 15.51 ± 0.32%, whereas the loss of weight in Aloe-treated grapes was 8.13 ± 0.59%. Apart from these, Aloe vera gel coating has also been effective in controlling water loss from other commodities, including pine-apple, sweet cherry, Granny Smith and Red Chief apples. This positive effect in terms of reduction of moisture loss may be due to the hygroscopic properties of Aloe gel that allow the formation of water barrier between the fruit and the surrounding environment. Thus, preventing its external transferences. Interestingly, Aloe vera gel mostly composed of polysaccharide which is highly effective as a barrier against moisture loss without incorporation of lipid.
American Journal of Food Science and Technology, 2014, Vol. 2, No. 3, 93-97 Available online at ttp://pubs.sciepub.com/ajfst/2/3/3
Journal