Preservation of frozen strawberries enriched with Saccharomyces boulardii using gelatin-based coating

Abstract

Although freezing is considered one of the easiest ways to preserve the quality of food, it is harmful to strawberries. Thus, the objective of this study is to evaluate the conservation of frozen strawberries using gelatin as a coating and of the probiotic yeast, Saccharomyces boulardii. Strawberries were selected, sanitized and subjected to the following treatments: Treatment 1 - control 1 (strawberries stored at -18ºC); Treatment 2 - control 2 (strawberries stored at -80ºC); Treatment 3 - strawberries added with citric acid, calcium chloride and S. boulardii stored at -18ºC; Treatment 4 - strawberries with gelatin, citric acid, calcium chloride, glycerol and S. boulardii stored at -18ºC. Drip loss, soluble solids, titratable acidity, color, firmness, ascorbic acid, total phenolic compounds, monomeric anthocyanins, antioxidant activity, polyphenoloxidase activity and viability of S. boulardii were analysed. The gelatin coating added with citric acid and calcium chloride, in combination with freezing at -18ºC, reduced the drip loss, the metabolic reactions and exerted a protective effect on bioactive compounds, making it possible to use them instead of deep-freezing, mainly for agribusinesses that do not have the equipment. The use of gelatin coating on strawberries minimized the effects of freezing and promoted the protection of S. boulardii, obtaining in up to 60 days of storage the minimum viable concentration of the microorganism to exercise its functional property. On the other hand, in the absence of gelatin, S. boulardii had a negative influence on the physical-chemical parameters, in addition to showing less viability. Thus, the study demonstrated that the coating composed of gelatin, citric acid and calcium chloride can represent an interesting alternative for application on frozen strawberries enriched with S. boulardii.