Developing final product specifications for long-grain parboiled rice (Oryza sativa L.) based on South African consumer preference

Thesis (MScFoodSc) -- Stellenbosch University, 2014.

ENGLISH ABSTRACT: The objective of this study was to determine the sensory and physicochemical characteristics of long grain parboiled rice that drive consumer liking, in order to generate a product specification that could ultimately be used for setting up a protocol, of processing parameters for long grain parboiled rice. A trained panel applied descriptive sensory analysis (DSA) to characterise the sensory attributes of 12 imported, commercially produced long grain, parboiled, rice samples. The rice samples were differentiated in both its raw and cooked format, by characterising its appearance, aroma, flavour and textural attributes. A consumer panel, comprising of 75 target consumers, rated preference for eight of the parboiled rice samples, in both its raw and cooked format, on a 9-point hedonic scale. Consumers, screened for the task, represented the key rice consuming ethnic groups from three major provinces within South Africa. In-depth consumer opinions and attitudes towards long grain parboiled rice were also examined, using the focus group technique. Physicochemical analysis were performed on all the rice samples, including colour measurement of both raw and cooked rice samples; firmness and stickiness measurement, viscosity measurement, degree of gelatinisation and the protein and amylose content of the samples. Analysis of variance (ANOVA) was conducted on the sensory and physicochemical data, as well as the consumer liking data. Multivariate analyses were performed on the sensory and consumer data, to determine whether relationships existed between the sensory and physicochemical sample attributes and consumer liking. Partial least squares regression (PLS) was performed, in an attempt to relate consumer degree of liking data, and the sensory and physicochemical data.

AFRIKAANSE OPSOMMING: The preferred raw rice samples were characterised mainly by the primary attribute of appearance, as having high whiteness intensity. The preferred cooked rice samples were mainly characterised by the primary attributes of appearance, (high whiteness intensity and swollen/plump appearance), and texture (slight stickiness in mouth, starchy mouthfeel after 5 chews and slight grain-to-grain stickiness). Sensory attributes of high firmness and springy/rubbery, and oily aroma mainly characterised the cooked samples that were not preferred. From a sensory perspective, the whiteness intensity, therefore, drives raw rice liking, whereas cooked rice liking is driven by a high degree of swollen/plump appearance, high whiteness intensity, and a relative amount of stickiness in mouth, starchy mouthfeel after 5 chews and grain-to-grain stickiness. Results show that consumers are not similar in their sensory requirements; attitudes and behaviour towards long grain parboiled rice therefore, differ. The physicochemical drivers, associated with both the raw and cooked preferred rice samples, were colour, degree of gelatinisation and viscosity properties. Based on the consumer preference for specific sensory characteristics of long grain parboiled rice, together with analytical measurements, consumer sensory demands can be translated into final product specifications. These specifications, in turn, can then be used as a first step toward setting up processing parameters, to ultimately achieve the desired quality of long grain parboiled rice.

Masters