ACCELERATED STORAGE TESTING OF FREEZE-DRIED IMMOBILIZED LACTOBACILLUS ACIDOPHILUS-FERMENTED BANANA MEDIA

Abstract

Freeze-drying was applied as a drying method for the production of dehydrated immobilized Lactobacillus acidophilus-fermented banana medium containing high levels of probiotics and appropriate prebiotic (mainly fructooligosaccharides) contents in an attempt to develop dried synbiotic products. Ca-alginate and κ-carrageenan were used for the immobilization of L. acidophilus, and the immobilized bacteria were employed directly in the banana media fermentation. The fermented products were then freeze-dried. Results indicated that cell immobilization could provide effective protection to L. acidophilus, and reduce the damage caused by freezing and freeze-drying. Meanwhile, accelerated storage testing using temperatures of 50, 60 and 70C was applied to the dehydrated products. Gel-entrapped L. acidophilus appeared to have lower decimal reduction, and Ca-alginate immobilized cells had a better survival than κ-carrageenan. Results of accelerated storage test showed that immobilization could effectively increase the thermal resistance of entrapped microorganisms, and Ca-alginate showed a better effect than κ-carrageenan, and the beneficial effects increased with the decrease of the storage temperature. The freeze-dried products exhibited little hygroscopicity because of the consumption of monosaccharides during fermentation. Results revealed that freeze-drying could be used as a proper method for the development of dried product of immobilized L. acidophilus-fermented banana media, and accelerated storage test could be used to evaluate the storage stability of the dried products. PRACTICAL APPLICATIONS This research demonstrates the feasibility of the application of accelerated storage testing to the prediction of shelf life and storage stability of freeze-dried probiotic products manufactured by lactic acid bacteria fermentation. The Arrhenius equation was associated in this study. This will provide an efficient approach for the estimation of shelf life of probiotic products.