Mitigation of aokusami (beany flavour) in a novel faba bean yoghurt

University essay from SLU/Department of Molecular Sciences

Abstract: Substituting dairy products for plant-based alternatives is a more sustainable choice. Plant-based alternatives are also a viable option for those who cannot or choose not to con-sume dairy-based products. Consumer trends point towards an increased consumption of plant-based alternatives over conventional dairy products. Today there is no pulse-based yoghurt on the market which is made from Swedish-grown legumes. Many products are instead based on overseas cultivated soybeans. Faba beans have been identified as a possible alternative to soybeans, being suitable for Swedish conditions and having a relatively high protein content. Hence, faba bean yoghurt has been postulated as a novel product. However, as in many pulse-derived products there is an issue with beany flavour (aokusami) which negatively impacts consumer acceptability. Aokusami is the result of oxidation of unsatu-rated fatty acids, forming hydroperoxides which further react forming flavour compounds (e.g. hexanal). This reaction can be spontaneous (autoxidation) or enzyme-catalysed by li-pid-modifying enzymes (LME) such as lipase, lipoxygenase and peroxygenase. Mitigation of beany flavour is possible by decreasing LME activity and autoxidation. The aim of this thesis was to investigate different production methods to mitigate aokusami in faba bean yoghurt. Methods employed for aokusami mitigation were: cold soaking (4 °C) of beans; thermal treatment of dry beans by microwaving; steaming of soaked beans (100 °C); blanch-ing of soaked beans (75°C); and, hot extraction (HE) of faba bean milk (75 °C, 80 °C, 85 °C, 90 ° C). Aokusami of produced faba bean yoghurt was assessed in sensory evaluations by panellists rating the product 1-5: from most aokusami to no aokusami. It was also inves-tigated if the aokusami mitigation methods would affect the incubation time, and if it was possible to predict aokusami of faba bean yoghurt by assessing faba bean milk flavour; re-sults were deemed inconclusive. Cold soaking led to a slight reduction of aokusami in the finished product. Thermal microwave treatment displayed insufficient aokusami mitigation. Blanching, steaming and HE ≤ 80 °C resulted in moderate reduction of beany flavour. HE ≥ 85 °C produced a yoghurt with complete mitigation of aokusami. Yoghurt produced by HE ≥ 85 °C yielded a gel whereas other production methods resulted in a thickness similar to that of drinking yoghurt. To produce a satisfactory viscosity in ≥ 85 °C HE faba bean yo-ghurt, enzymatic hydrolysis of amylose and amylopectin is proposed. However, further studies of texture and mouthfeel need to be conducted before faba bean yoghurt becomes a developed product.

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