Production of lactic fermented beverages by using water-soluble oat extract

Fermented lactic beverages are traditionally obtained by the fermentation of milk by cultures of lactic bacteria (LAB). These beverages may present probiotic characteristics as a function of the kind of culture and quantity of viable cells that are present at the end of fermentation and during shelf life. On the other hand, the use of milk as a raw material means that such beverages can not be consumed by certain consumers (individuals that are lactose intolerant, allergic to milk protein and/or vegan consumers). Therefore, the use of different raw materials for the production of lactic fermented beverages, such as plant extracts, are an alternative to serve specific groups and also consumers that search for foods and beverages that can potentially have a healthier consumption appeal. The aim of this study was to evaluate the production of lactic fermented beverages by using water-soluble oat extract. In order to produce the extract, oat and water were mixed in the proportion 5 % w/v of oat. This mixture was then triturated in a blender for 10 minutes at 35 °C and filtered in a cotton cloth. The obtained extract was pasteurized at 85 ºC/ 5 min and cooled to 37 °C in order to carry out the inoculation of the lactic culture. A lyophilized commercial culture containing Streptococcus thermophilus, Lactobacillus acidophilus LA-5 and Bifidobacterium BB-12 of the Bio Rich® brand (made by Christian Hansen A/S of Denmark) was used, in the proportion of 400 mg/L, enough for the initial counting of 106 UFC/mL. The fermentations were carried ou in Erlenmeyer flasks of 300 mL with an extract volume of 250 mL in an oven (Orion 502, FANEM) at 37 °C for 12 hours, without stirring. Two conditions were evaluated: (i) with the original extract and (ii) with the extract with added sucrose and standardized to the initial soluble solid concentration of 5 ºBrix. Analyses of acidity (A), pH, soluble solids concentration (SS), dry extract (DE), ashes (AS) and lactic bacteria counting (LAB) were conducted. The obtained results were A = 0.15 and 0.17 % w/v; pH = 4.97 and 4.12; SS = 1.0 and 4.0 °Brix; DE = 6.15 and 8.31 % w/w; AS = 0.01 and 0.01 % w/w; LAB = 5.9 x 108 and 5.0 x 108 UFC/mL, for fermented beverages without and with initial SS adjustment, respectively. Results show that there was acidification of the medium, with pH reduction (whose initial value was of 6.60) and growth of LAB, whose value increased in 2 log UFC/mL after 12 hours of fermentation. These two parameters indicate that the LAB were capable of fermenting both the original and sucrose supplemented oat extracts, producing lactic beverages from this subtract. The reduction of pH was greater in the sucrose supplemented extract, but the growth of LAB was similar in both conditions. The final DE was greater in the supplemented extract, due to the presence of greater quantities of sugar in the medium, and AS suffered no variation during the fermentation process. The obtained beverages may be considered as probiotics according to the Brazilian legislation, as it contains microorganisms with this characteristic and the LAB countings at the end of fermentation were higher than 106 UFC/mL, the minimum necessary to confer the probiotic attribute. The study showed that the water-soluble oat extract (with and without sucrose supplement) is a viable extract to obtain probiotic lactic fermented beverages, and presents the advantage of producing a beverage with no lactose and milk proteins, supplying the demand of consumers with dietary restrictions to these nutrients.