The cross-over fermentation concept and its application in a novel food product: The dairy miso case study

Cross-over fermentations are processes in which a microorganism from one traditional fermentation process is introduced onto a new substrate and/or to a new partner. Here we show that Aspergillus oryzae normally used for the production of miso, a fermented soybean paste from Asia, can be applied to a traditional European fermented dairy product quark cheese, produced by fermenting milk with Lactococcus lactis. This cross-over fermentation resulted in a product with intense aroma properties, mainly due to high amounts of volatile fatty acids, ethyl esters, higher alcohols and ketones. Active metabolism of A. oryzae was required for alcohol production, whereas fat degradation occurred mainly due to enzymatic activities. Traditionally used practices in miso production, like mixing, addition of various amounts of salt and variations in fat content of the substrate altered metabolic and enzymatic properties of A. oryzae resulting in differences in final product characteristics. Aroma intensity of the product was shown by comparing volatile organic compounds with blue and white mould cheese. This study showed the potential of cross-over fermentation for novel food products. The enormous diversity of microorganisms used in traditional fermentation processes and the vast number of alternative substrates offer numerous opportunities for further novel fermented product development.