Microbiological quality and some bioactive compounds in relation to sensory profiles during germination of brown-purple-pigmented rice

Brown rice contains many nutrients such as carbohydrates, proteins and bioactive compounds such as GABA and antioxidant compounds (e.g. anthocyanins and phenolic compounds). These may increase during grain germination which in turn could affect the sensory attributes. Therefore, the present work was aimed to study the effect of different germination times (24, 36 and 48 h) on changes of the bioactive compounds, the physical parameters in colour, texture properties and sensory attributes of germinated glutinous purple brown rice, Niew Dam (NDGBR) and germinated non-glutinous purple brown rice, Hom Nil (HN-GBR). The germination of the two cultivars led to the differences in GABA, polyphenolic compound content, and DPPH radical scavenging activity. The ND-GBR yielded higher GABA and polyphenolic compounds than those found in HN-GBR. Moreover, the aerobic mesophilic bacteria and yeasts and mould were found in the early phase of germination, but the lactic acid bacteria (LAB) were found in the late phase of the course. The physical properties including colour, textural properties and sensory characteristics were examined. The cooked HN-GBR was more polished than the cooked ND-GBR with longer time of germination. The samples had positive a* values and negative b* values. The cooked ND-GBR was harder but had higher chewiness than the cooked HN-GBR. The result indicated that the germination of rice could improve the softness of the GBR texture. These interactions provided the unique characteristics in sensory profiles. It was found that HN-GBR provided high endurance rice bran and fermented odour. Meanwhile, the deeply purple-coloured, rubbery and gluey-like attributes, oiliness and brittleness are unique attributes for ND-GBR. Furthermore, the stickiness, the steamed banana leaf-like odour and the glossiness and less sweetness were dominantly in longer germinating time of ND-GBR.