Sorghum-soya biscuits: effect of repeated exposure on consumers’ acceptability

Abstract

The imbalance between the demand and supply of wheat in Africa has created a need for utilisation of climate smart African cereal grains such as sorghum in the production of a variety of products. However, sorghum as an ingredient is unfamiliar in the South African commercial biscuit market hence thorough consumer acceptability research before any product launch is vital. Traditional consumer sensory research methods to determine consumer acceptability of novel foods might not be sufficient because the measurements are usually limited to immediate impressions. Therefore, a better prediction of acceptability of novel foods such as sorghum biscuits is expected when employing repeated exposure consumer tests. The first part of the study was done to develop suitable wheat only (control), sorghum only, sorghum-soya and wheat-soya biscuits and characterise the physical, textural properties of these biscuits prior to consumer testing. Adjustments of the formulations, dough handling and baking parameters were necessary to cope with the different properties of the respective flours and doughs. In terms of the physical characteristics, wheat only biscuits were heavier and thicker than the sorghum-soya biscuits. This could be ascribed to the elasticity of the wheat dough which caused the dough to spring back after sheeting resulting in biscuits that are thick and heavy. Wheat biscuits were also found to be harder than sorghum-based and wheat-soya biscuits. Biscuits containing sorghum or soya flour were darker (lower L* value) and with more redness (higher a* value) than the wheat-based biscuits. Increased redness in sorghum biscuits was due to the red-pericarp layer of the red non-tannin sorghum flour that was used for preparation of the biscuits. The darkness in sorghum-based biscuits is attributable to the dark brown colour of sorghum flour. The increased yellowness (b*) in wheat-based biscuits attributed to the wheat endosperm which has a pale yellow colour. The second objective of this research was to determine the hedonic adjustment potential of the novel sorghum biscuits through conducting repeated exposure testing of biscuits by young adults. Four biscuit formulations used as test material were 100 % sorghum, 100 % wheat, 70:30 sorghum-soya and 70:30 wheat-soya on a flour component base. Participants (n = 155) were randomly allocated to five experimental groups of 31 each. One group did not receive biscuits to consumer for 20 days and this group was called the non-exposure group. The participants in the remaining four groups were given 20 biscuits (1 biscuit type per group) to taste and evaluate, one biscuit per day, for 20 days. All participants however evaluated all four biscuit formulations during the pre-exposure, post-exposure and follow-up test sessions. 100 % sorghum and sorghum-soya biscuits were regarded as unfamiliar or novel biscuits. For the group that was repeatedly exposed to sorghum-soya biscuits for 20 days, significant increases in liking of sorghum-soya biscuits during the 20-day exposure phase were observed when results of the pre-exposure session were compared to that of the 20-day exposure phase. Results also showed that there was a decrease in liking of 100 % wheat biscuits on day 1 of the 20-day exposure phase for the group that was repeatedly exposed to 100 % wheat biscuits for 20 days when the pre-exposure results were compared to that of the 20-day exposure phase. The decrease in liking for 100 % wheat biscuits is probably due to the fact that, wheat biscuits were indeed not complex to consumers hence exposure to a non-complex stimuli led to boredom and product boredom has been attributed to the decrease in liking of food products during repeated exposure. On the contrary, results obtained from the sorghum-soya group might be due to the fact that the sorghum-soya biscuits were too complex for consumers but over time the complexity or novelty factor gradually reduced which caused an increase in appreciation of sorghum-soya biscuits. The non-exposure group rated wheat-soya biscuits higher than the group that was exposed to wheat-soya biscuits for 20 days. These results could have happened because of product irritation which occurred to the group that was exposed to wheat-soya biscuits for 20 days. Although 50 % of participants showed high neophobic tendencies, food neophobia propensities did not have an effect on liking of all biscuit formulations. This is might have occurred because, 82 % of the participants indicated that they were familiar with sorghum thus their neophobic tendencies did not have an effect on liking of sorghum-soya or 100 % sorghum biscuits. Findings from this study demonstrate that repeated exposure can be used as a strategy for predicting long-term preferences and potential acceptance of sorghum-soya biscuits. Results also demonstrated that exposure to familiar products can lead to product boredom which causes a decrease in liking.