ANALYTICAL CONTROL OF CIDER PRODUCTION BY TWO TECHNOLOGICAL METHODS

Two cider-production procedures involving direct fermentation of apple juice and a prefermentative clarification step or defecation were controlled microbiologically, while chemical monitoring of the major sugars, polyalcohols and organic acids produced during the fermentation was carried out by HPLC. The defecation process markedly slows down alcoholic fermentation and the malolactic conversion. Good correlations between the contents of D(–) lactate and volatile acidity were obtained for the ciders studied, which indicates that the increased volatile acidity of the ciders was basically a result of metabolism mediated by lactic-acid bacteria, the yield being higher in barrels where enzymatic defecation was not applied. Sucrose was rapidly hydrolysed in the first step of the fermentation process, while glucose is the preferential carbon source for the yeasts. Citric acid was produced by the yeasts in the first step of the fermentation process and was later taken up by these micro-organisms. Conversion of quinic and shikimic acids seemed to point to a signicant activity of heterofermentative lactic-acid bacteria in storage and maturation of ciders.