Effect of Different Conditions of Growth and Storage on the Cell Counts of Two Lactic Acid Bacteria after Spray Drying in Orange Juice

Abstract

Consumers increasingly require innovative food products with health benefits. Thus, a dried orange juice incorporating probiotics could be a novel challenge. In this context, we investigated whether different sugars added to the culture media used for growth of two lactic acid bacteria contributed to their protection during spray drying in orange juice and subsequent storage under different conditions of temperature, light exposure and water activity. Cell viability during passage through simulated gastro-intestinal conditions was also investigated. Cells grown in culture medium containing fructose resulted in the worst survival rates during storage. High survival was observed for cells grown in the presence of lactose, followed by glucose. The survival of dried bacteria was enhanced at 4˝C, water activity of 0.03 and absence of daylight. For cells grown in standard culture medium and after 12 months of storage at 4˝C in orange juice powder (about 10 9 cfu/mL), there was a reduction of approximately 2 log-units for both lactic acid bacteria after gastro-intestinal tract passage simulation. Using the conditions of growth and storage investigated, it is possible to improve the survival rate of lactic acid bacteria and produce an orange juice powder with probiotic characteristics with shelf life of at least 12 months.

Development of milk powder containing Lactobacillus plantarum NCIMB 8826 immobilized with prebiotic hi-maize starch and survival under simulated gastric and intestinal conditions

“…The powder was collected in a pre-weighed polyethylene bag and the mass of powder was obtained. The drying yield was determined as the percentage of total solids in the liquid feed that were recovered from the collection vessel attached to the cyclone (Barbosa et al 2016). The powder from each sample was weighed and placed in aluminum bags.…”

Microorganism preservation by convective air-drying—A review

“…Spray drying is a technique of converting liquid or slurry into dry powder by rapidly injecting the atomised slurry into a current of hot air [54,87]. Spray drying employs quick heat-mass transfer and generates high-quality powder that could closely resembles the original product after rehydration [89].…”

“…Furthermore, several other factors add on to concerns regarding low survival during spray drying and low stability during storage for application for microorganisms [95]. Factors that play a big role in survival and stability include drying temperature & duration, particle size, type of species/strain to be dried, culture medium, and whether or not pre-adaptation and/or protectants are added [54,96]. Under the right condition, spray drying of lactic acid bacteria can be conducted to achieve sufficiently high retention of cell activity and viability with even comparable quality to those produced through freezedrying [87].…”

“…Convective hot air circulation oven drying is developed as an improvement from conventional thermal drying by introduction of air circulation [20]. Study conducted between convective hot air circulation oven drying and conventional thermal drying on kefir biomass reveals that the convective method gives higher drying rate, as moisture content is removed more rapidly by circulated air stream [54]. In addition, the final dry weight of kefir is the same for both methods, and consistent results were obtained at drying temperatures of 28, 33, and 38°C [31].…”

“…In freeze-drying, much higher energy needs to be supplied to induce sublimation in order to vaporise the frozen water molecules whereas convective air drying only relies on evaporation [52]. Based on study conducted by Rudy (2009), freeze drying consumes approximately 3.3 MJ/h while convective air drying consumes 3.05 MJ/h for every kg of wet starting material [53,54]. Although the energy consumptions might not seem to differ greatly, it should be noted that the analysis has not taken into account the pre-freezing process of freeze drying which could also significantly adds to the energy consumption [53].…”