Development of a functional orange juice powder by spray drying

The concept of functional food products has acquired a huge dimension with the enormous number of people concerned about consuming foods with health benefits. An innovative non-dairy functional food would be very attractive, not only to these consumers but also to specific niches in the market (e.g. lactose intolerants and vegetarians). The aim of this work was to develop a powdered functional orange juice. For this, cultures with probiotic characteristics were used and the necessary conditions to obtain the dried product by spray drying were defined. Two cultures were selected, a commercial probiotic, Lactobacillus plantarum 299v and an isolate from a food matrix, Pediococcus acidilactici HA-6111-2. Safety and the presence of some functional characteristics of P. acidilactici were investigated and compared with those of the commercial probiotic. None of the bacteria produced any of the virulence factors investigated; they did not exhibit significant resistance to antibiotics and reductions lower than one logarithmic cycle were observed after exposure to simulated gastro-intestinal tract conditions. It was also verified that both bacteria survived during the spray drying process and subsequent storage for 60 days. Powdered orange juice was initially obtained in a Büchi Mini Spray Dryer at constant feed temperature (ºC), flow rates of feed (mL/min), drying air (%) and compressed air (L/h) and varying inlet and outlet air temperatures (ºC) as well as the ratio of total soluble solids (orange juice): drying aid (10DE maltodextrin or gum Arabic). At selected inlet and outlet air temperatures of 120 ºC and 65 ºC, respectively, and ratio of soluble solids: drying aid of 0.5: 2, high drying yields and powders with low water activities (aw) were obtained. No cell inactivation was observed for each culture after incorporated into orange juice and spray dried. Their survival during storage at 4 ºC was higher than at room temperature under uncontrolled aw. Pediococcus acidilactici was more resistant than L. plantarum, especially during storage at 4 ºC, with logarithmic reductions lower than 1 log-unit during a period of at least seven months. To enhance survival of spray dried bacteria during storage, different pre-spray drying conditions were tested: i) different sugars were added to the culture media used (cell growth in the presence of lactose, followed by glucose resulted in the highest survival) and ii) cells were exposed to different sub-lethal stresses (only survival of L. plantarum cells during storage at room temperature was increased). For both cases, powders obtained were stored under different conditions of temperature, light exposure and aw. Generally, survival was enhanced at 4 °C, aw of 0.03 and absence of light. Cell viability during passage through simulated gastro-intestinal tract conditions was also investigated at the end of the storage at 4 ºC; the viability of both cultures was not enhanced by prior exposure to sub-lethal stresses. Survival of cultures in orange fruit powders obtained by spray-, freeze- and convective hot air drying was investigated during drying and subsequent storage. Cell inactivation was only observed during convective hot air drying (about 2 logarithmic cycle reduction). Minimal reductions were observed for P. acidilactici for most conditions of storage while for L. plantarum only during storage at 4 ºC. Taking into account the initial number of cells obtained after each drying process, the techniques which allowed survival of an increased number of cells after storage, were spray- and freeze drying. Better dissolution, color and vitamin C retention were also obtained when these techniques were used. Despite the scale-up and validation at industrial scale being still necessary, spray drying at pilot scale allowed producing a new functional orange juice powder with probiotic characteristics. The bacteria used demonstrated to be good candidates for the development of this product.