Relationships of sensory profile with instrumental measurement and consumer acceptance of Thai unpolished pigmented rice

Since being recognized for its health benefits, consumption of unpolished pigmented rice has increased markedly. The objective of this study is to investigate the sensory profile and the relationship between physical/chemical properties and consumer acceptance of 12 Thai unpolished pigmented rice samples (5 non-glutinous black rices, 3 non-glutinous red rices and 4 glutinous black rices). Descriptive analysis evaluated by 10 trained panellists showed that glutinous rice had higher intensities of sticky and smooth textures, mixed berry/popcorn odour and flavour as well as appearance characteristics including adhesion, plumpness, glossiness, darkness but lower intensities of hardness and husk flavour than non-glutinous rice (p<0.05). Physical property analysis revealed that both instrumental hardness of non-glutinous black rice and colour (L* , a*, b*) of non-glutinous red rice were higher than those of glutinous black rice (p<0.05). However, glutinous black rice obtained higher values of size, weight, elongation index (EI), total anthocyanin content and total phenolic content than other rice samples (p<0.05). Multi Factor Analysis (MFA) demonstrated the relationship on the first three principal components (PCs1-3) with 79.61% of total variance. Appearance attributes (darkness, plumpness, adhesion, glossiness), sticky and smooth textures, sweet flavour, mixed berry/popcorn odour and flavour as well as physical properties (width, thickness, EI, weight, stickiness, hardness and colour) and some chemical properties (total anthocyanin content, total phenolic content, amylose content) were highly correlated on PC1 and associated with glutinous black rice. While musty and soil odours as well as husk flavour were associated with the red rice group. The results of the acceptance test showed that Thai consumers preferred unpolished pigmented rice with low intensities of hardness, glossiness, adhesion, plumpness and bursting as well as low values of width, thickness, weight and EI which were mainly found in MNS, HNU, RB, HNP and HNL.