Designing Processing and Fermentation Conditions for Long‐Life Set Yoghurt for Made‐in‐Transit (MIT) Product

AbstractExtending yoghurt fermentations could facilitate yoghurt distribution by allowing the fermentation to occur during transportation – a concept known as “made‐in‐transit” (MIT). The objective was to determine the starter culture composition, inoculum size and fermentation temperature for extending yoghurt fermentations to 168 h. The yoghurt was processed using a milk base sterilized by ultra‐high temperature (UHT) treatment at 138C for 6 s. Factorial experiments for yoghurt processing were designed with starter culture combinations of STLB (Streptococcus thermophilus with Lactobacillus delbrueckii subsp. bulgaricus) and STLA (S. thermophilus with L. acidophilus), inoculum sizes of 2.0 and 0.2% (v/v) and fermentation temperatures of 25 or 35C. The fermentation was monitored over 168 h using pH, starter culture concentration and firmness. The combination of STLA, and a 0.2% inoculum, fermented at 25C extended the yoghurt fermentation to 168 h; however, no gel formed. The best product was produced with a STLB starter combination of 2.0% inoculum fermented at 35C for 24 h. This shows the constraints and limitations of applying the MIT concept to a fermented food.Practical ApplicationsYoghurt produced using an extended fermentation time to allow fermentation during transportation, could allow product to be shipped to distant markets and extend the shelf life in the market. A UHT‐treated milk base will be needed to ensure no growth of contaminants, and this will also help to ensure a longer product shelf life. The fermentation conditions obtained in this study provide an opportunity for extending the yoghurt market reach by up to 7 days (168 h) of transportation.