INHIBITORY EFFECT OF TANNIC ACID EXTRACTED FROM GRAPE SEEDS AND POMEGRANATE PEELS ON SOME MICROORGANISMS

Abstract

The study included extraction of tannic acid from grape seeds and pomegranate peels , their content of tannic acid were 4.1 and 27.6 g/100g (dry weight), respectively .The quality tests which done on extracted tannic acid from both sources showed positive results, where the increasing tannic acid concentration leads to increase killing effect on studied microorganisms especially at highest concentration (2%) .These results showed that extracted tannic acid from both sources can be used as preservation material in food processing and component of cosmetic materials and pharmacological drugs. INTRODUCTION Tannins are water soluble polyphenols that present in many different parts of plants(Akiyama et al.,2001), such as Oak tree galls, Peels of banana and pomegranate fruits, fruits of date tree and apple, seeds of coffee and grape as well as in many tropical plants (Huang et al., 1993) .Tannins also play an important role in acceptability of food products and their chemical structures are different, though they have a distinguishing astringent taste (Chung et al.,1998) .Tannins compounds classified into two groups: hydrolyzable tannins, and; non hydrolyzable tannins. The first one is ester of phenolic acids with sugars (Scalbert,1991) .Tannic acid was identified according to Deyeux and Segeux in1795 (The Birtish Pharmaceutical Codex, 1911). It is Gallotannin which is ester of gallic acid with glucose and then classified as hydrolyzable tannins (Miranda et al., 1996) .Tannins compounds were used in many industrial applications, such as juices clarification and antioxidant material when added to many food products and beverages (Khan et al., 2000), also in oil refining and in preservation of marine meat fish and in manufacture of blue ink (Huang et al., 1993) and a component of cosmetic products and pharmacological drugs due to their activity against chronic dysentery, stimulating healing and treatment cholera and its best antidote against poisonous mushrooms (Chung et al., 1993). Chung et al. (1998) and Scalbert (1991) reported that tannic acid has inhibition effect on many different species of food born bacteria like Aeromonas hydrophila, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Salmonella typhi and Enterococcus faecalis . Heil et al. (2002) observed that tannins compounds have inhibition act on some fungi. Many studies had done on extraction of some chemical compounds from plants to identify their quantity, quality properties and inhibition effect on microorganisms (Cowan, 1999), but they didn't take it in consideration to use by products of food processing like pomegranate peels and grape seeds as a source of tannic acid. The main objective of this research is to extract tannic acid from grape seeds and