Microwave treatment of grapes: effect on the must and red wine polysaccharide composition

Abstract

AIM: The application of microwaves (MW) to the grape is a technique to reduce the contact time with pomace because it allows to break the cell walls of the berry. The objective of the study was to investigate the changes in the composition of polysaccharides in Cabernet-Sauvignon musts and wines made with grapes treated with microwaves.

METHODS: Red grapes were destemmed and crushed and divided into two batches. One batch was treated with MW at 700 Watts for 12 min and the other batch was not treated to be used as control. Three control microvinifications and three microvinifications treated with MW were carried out, all of them with three days of maceration. The content of each polysaccharide family in the samples was estimated as described by 1 and 2. MW improved the breakdown of cell walls of crushed grapes, thereby it significantly increased the content of polysaccharides rich in arabinose and galactose (PRAG), rhamnogalacturonans-II (RG-II), homogalacturonans (HL) and mannans/mannoproteins (MP) in musts. However, no significant differences were observed between the control and MW wines in the content of PRAG, RG-II, HL and MP. 

CONCLUSIONS

MW allowed to increase the release of polysaccharides in must, although its effectiveness was not maintained in wines