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

Belén Ayestarán¹, Leticia Martínez-Lapuente¹, Mikel Landin¹, Raquel Muñoz García², Zenaida Guadalupe¹
1Instituto de Ciencias de la Vid y el Vino (Universidad de La Rioja, Gobierno de La Rioja, CSIC), Finca de La Grajera, Ctra. Burgos 6, 26007 Logroño, España
2Facultad de Ciencias y Tecnologías Químicas (Universidad de Castilla-La Mancha), Avda. Camilo José Cela, s/n, 13071 Ciudad Real, España

Email contact: belen.ayestaran@unirioja.es

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.

References:

1 Guadalupe, Z., Martínez-Pinilla, O., Garrido, A., Carrillo, J. D., & Ayestarán, B. (2012). Quantitative determination of wine polysaccharides by gas chromatography–mass spectrometry (GC–MS) and size exclusion chromatography (SEC). Food Chemistry, 131, 367–374.

2 Ayestarán, B., Guadalupe, Z., & León, D. (2004). Quantification of major grape polysaccharides (Tempranillo v.) released by maceration enzymes during the fermentation process. Analytica Chimica Acta, 513, 29–39.