Survival of Lactobacillus helveticus CNRZ32 in spray dried functional yogurt powder during processing and storage

Abstract

Fresh set-yogurt fortified with functional lactic acid bacteria (Lactobacillus helveticus CNRZ32) was manufactured in two sets, plain and supplemented with butter milk powder. All samples were spray dried at two specific inlet air temperatures 150 °C and 120 °C, with a fixed outlet temperature at 60 °C. The survival of L. helveticus in the yogurt powder after spray drying and during storage for several months was evaluated using bacterial count and survival percentage as two main criteria. Results indicated that L. helveticus CNRZ32 can survive for three months in the powder obtained by spray drying at 120 °C. The survival percentage at the end of that period was ~80.0% with an acceptable count of 6.0 log cfu/g. Supplementation of the fresh yogurt with butter milk powder during processing and before spray drying can prolong the survival period of L. helveticus up to four months with acceptable count and survival percentage. Evaluation of the viability of L. helveticus in the powder at its maximum storage period (four months) was performed. Results showed that a four-month stored powder can initial the formation of new fresh set-yoghurt containing L. helveticus and starter bacteria at satisfying counts above 6.0 log cfu/g without using external starter culture or new supplementation of L. helveticus. These results could have potential application in the production of L. helveticus incorporated within yogurt powder using spray drying for fortification and functionalization of innovative food and dairy products.