Determining the quality of fiber enriched strawberry juices by means of FTIR spectroscopy and multivariate analysis

GERBINO, ESTEBAN; GÓMEZ-ZAVAGLIA, ANDREA; CASSANI, LUCÍA; SANTOS, MAURICIO; QUINTANA, GABRIEL; MOREIRA, MARIA

Amsterdam

Congreso; 17th European Conference on the Spectroscopy of Biological Molecules (ECSBM); 2017

The European Conference on the Spectroscopy of Biological Molecules

INTRODUCTION The stability of soluble sugars present in fruit juices (i.e.: glucose, fructose, sucrose) and that of those eventually added as nutritional ingredients [fructo-oligosaccharides (FOS), inulin] are important quality factors for the food industry, as they are direct indicators of the quality and authenticity of fruit-based products, directly related with consumer expectations. For this reason, determining variations in the sugar content in fruit juices is an important indicator of adulteration or contamination, and even deterioration during storage.The aims of this study were: 1) to identify and quantify the main carbohydrates and FOS present in fiber-enriched strawberry juices preserved using non-thermal techniques both in the freshly prepared and in the stored products; 2) to develop a rapid, simple and non-destructive analytical technique to monitor the quality of juicesMATERIALS AND METHODSStrawberries (Fragaria x ananassa Duch.) were processed with a juicer. The obtained juices were divided in four groups: a)Juices without any addition (controls), b)Juices enriched only with an inulin/oligofructose mixture, c)Juices enriched with inulin/oligofructose and treated with geraniol, d)Juices enriched with inulin/oligofructose and treated with vanillin and ultrasound. All the four beverages were stored at 5 ºC for 0, 3, 7, 10 and 14 days. At each storage time, the juices were freeze-dried for further HPLC and FTIR analyses.RESULTS ANS DISCUSSION Using two different HPLC columns (Sugar Pak and Ultrahydrogel Column Linear) allowed a nice and clear separation of mono and disaccharides, FOS, inulin, pectins and citric acid present in strawberry juices. After identifying these compounds, they were quantified and used as reference method, in the PLS analysis.Principal component analysis showed different groups related to changes in the carbohydrate composition during storage and explained more than 94% of the variance.Partial least square (PLS) models were defined and independently validated to predict the concentrations of fructose, glucose, sucrose, tri, tetra and penta-FOS both in the freshly prepared and in the stored juices. The mean of predicted values fitted nicely those obtained by HPLC (R2: >0.97), thus demonstrating the reliability and robustness of the calibrated models. This supports the use of the PLS model to monitor the quality of strawberry juices in unknown samples.