Viability of probiotic bacteria in a maple sap beverage during refrigerated storage

Abstract

There is an increasing demand for non-dairy probiotic foods made from raw materials. This study assessed the ability of maple sap concentrate diluted to 2, 5, and 8 ºBx to maintain the viability of probiotic bacteria inoculated at 108 and 1010 CFU/portion of 40 mL and stored for 12 weeks at 4 °C. Three two-strain and one three-strain combinations of Lactobacillus rhamnosus R0011, Lactobacillus helveticus R0052, and Bifidobacterium animalis subsp. lactis BB12 were analyzed. Survival was monitored by selective plate counting and viability was assessed by quantitative PCR following propidium monoazide treatment (PMA-qPCR). Results showed a lower survival of mixed cultures of R0052 and BB12 inoculated at 1010 CFU/portion than survival values obtained at 108 CFU/portion. Culturable and viable counts from sap inoculated at 1010 CFU/portion were significantly lower in sap diluted at 2 ºBx for every combination, highlighting the protective role of sap components at higher total soluble solids concentration. The ability of maple sap concentrate to maintain probiotic viability was readily and accurately determined by PMA-qPCR. According to this study, concentrated maple sap was able to maintain high viable and survival counts of carefully selected probiotics, demonstrating its potential as fluid for the production of a probiotic beverage.