Factors controlling the deterioration of spray dried flavourings and unsaturated lipids

Despite many years of research, the industry still struggles with improving the shelf-life of oxidizable food components (e.g. flavourings, polyunsaturated triglycerides, natural pigments, vitamins, flavourings etc.) or highly volatile components (e.g. aroma components in flavourings). Microencapsulation has been serving as an effective way to preserve flavour and other active ingredients, to control their release rate, and/or to mask their unpleasant odour or taste. Among a variety of microencapsulation methods, spray drying is the most widely used process in the food and beverage industries, due to its ease of processing and low operating cost. Unfortunately, most food encapsulating materials (hereafter called 'wall materials') are not the best barriers so the desired shelf-life of encapsulated flavourings and other active ingredients is difficult to achieve. However, significant progress has been made through research on encapsulation formulations, processes, and evaluation technologies. This review summarizes the information in the scientific literature on how to optimize both the encapsulation matrix and the process to maximize product shelf-life. This review presents literature from both the 'oil' and flavour areas. While there are some different issues in preserving highly unstable oils vs. flavourings, there is significant overlap. It is worthwhile to summarize, analyse and critique the literature in these two domains so both industries and academia can benefit from the sharing of this knowledge. First, factors that influence permeability of wall materials and microcapsules are discussed. Then, deterioration of flavourings or unsaturated lipids microencapsulated by spray drying is reviewed. The final section offers thoughts as to ways to improve upon the current practices.