Vacuum Impregnation of Probiotics in Fruit Pieces and Their Survival During Refrigerated Storage

Abstract

Even though probiotics are currently available mainly in dairy products, interest in the incorporation of probiotics in other foods has been increasing. This research aimed to develop probiotic foods by fortifying the probiotics in partially-dried fruits using a vacuum impregnation technique. Fruit (guava and papaya) pieces were impregnated under a vacuum pressure of 50 mBar with three types of extracted fruit-juice solutions: 15°Bx extracted and 30°Bx extracted fruit juices containing 10¹⁰ cfu/mL of Lactobacillus casei 01 for 5, 10 and 15 min, respectively. After impregnation, the fruit samples contained amounts of the probiotics ranging from 10⁸ to 10⁹ log cfu/g. The impregnation time and the soluble-solid contents of the impregnated solution affected vacuum impregnation parameters such as the impregnated sample volume fraction (X) and the effective porosity (ε_e). No change or only a slight change in the volumetric deformation (γ) of the fruit pieces occurred after impregnation. The solublesolid contents also influenced the level of probiotics in the products. If the amount of soluble solids was either too low or too high, then the viable count of the probiotics was reduced. In order to increase the storage stability of the products, the impregnated guavas and papayas, which had been impregnated with fruit juice containing 15°Bx for 10 and 5 min, respectively, were dried at 40°C for 36 h and kept at 4°C for four weeks. The viable cell counts of L. casei 01 in both impregnated guavas and papayas were approximately 107 log cfu/g, which reached the therapeutic minimum level of dairy products.