Starchy Supports: Immobilization and Wine Making

Abstract

In last decades cell immobilization for alcoholic fermentation is a rapidly expanding research area and several immobilized cell systems have been proposed and studied. However, applications of this technology at industrial scale are limited. It is important the supports that will be used for immobilization in food industry to be of food grade purity in order the final product to be suitable for consumption. Therefore many research works have been published concerning the use of food grade purity supports in wine making. Some examples are the use of gluten pellets [3], dried raisin berries and grape skins [4,5], and fruits such as quince, apple, pear [6], guava [7], watermelon [8] and dried figs [9]. The use of these immobilized supports led to the production of high quality wines with improved aroma. In addition the aroma of these products, produced using fruits as immobilization supports, was characterized fruity. Nowadays another important aspect for successful industrial application of this technology that should be taken into consideration during selection of supports suitable for immobilization is that they must ideally be abundant in nature and cost effective. The use of the above mentioned supports may lead to an increase in the price of the final product something that is not preferred. Therefore in such products, like wine and beer, it is important to use as immobilization supports products abundant in nature, ease to handle and especially of low cost. A promising proposal for such supports is starchy supports. Starchy supports are mainly referred to products such as potato, corn, wheat, barley and products that derive from them. Potato The use of potato pieces as immobilization support of yeast for wine making has been investigated and the results were very promising [10]. More specifically this biocatalyst retained its operational stability for a long period and in a wide range of fermentation temperatures ranging from 25 to 2 ° C producing wines of fine clarity. Regarding the effect of the biocatalyst in the aromatic profile of the wines the SPME– GC–MS (Solid Phase Micro-Extraction – Gas Chromatography – Mass Spectroscopy) analysis showed that the immobilized cells produced wines with improved aroma compared to the wines produced by free cells. In addition the percentages of the total esters on total volatiles were increased by the drop in temperature, while percentages of alcohols were reduced. Finally a possible catalytic effect of the potato pieces in alcoholic fermentation was reported and was proved by the calculation of activation energies. The results showed that the activation energy of the immobilized cells was 44% smaller than that of free cells while the corresponding fermentation rate constant k was higher in immobilized cells.