Review on factors affecting and control of post-acidification in yoghurt and related products

Background: Yoghurt and related products relish vast consumption pattern worldwide. The quality of such products depreciates during chilled-chain storage and transportation due to residual metabolic activity of viable starters leading to post-acidification, which in turn reduces product's shelf-life, decreases consumer acceptance and is even detrimental to stability of probiotics. This phenomenon is predominant in tropical and resource-poor nations, hence, there is growing interest to curb post-acidification without affecting product's quality. Scope and approach: This review summarizes recent findings on various associated factors (starter type, milk composition, processing parameters, pre- and pro-biotics and packaging material), conventional and emerging approaches spanning the domains of food processing, microbiology and preservation to combat post-acidification in yoghurt and related products. Shortcomings and future scope of strategies have also been discussed which will provide new avenues for the researchers to work forward in improving the quality and shelf-life of fermented products. Key findings and conclusions: Thermal treatment of fermented products indisputably controls post-acidification but also destroys heat labile beneficial peptides and microbes. Emerging techniques like HHP, PEF, ultrasound etc. could potentially be used for the development of mild flavor shelf-stable fermented products. However, cost-effectiveness, optimization of process parameters and specific legal requirement should be considered. Control via legally permitted preservatives or additives is feasible provided desirable sensorial attributes are not altered. Direct incorporation of bacteriocins in yoghurt is hindered by its high purification cost and stability in food matrix. Bioprotective cultures and strain improvement through random mutagenesis have been employed successfully for in-situ aversion of post-acidification.