Effect of Matcha green tea powder in shortbread biscuits on consumer acceptability and acute metabolic response

Matcha green tea powder (MGTP) is made by finely grounding green tea leaves and is increasingly used to flavour food products. The aim of this thesis was to produce a shortbread biscuit product containing MGTP and to evaluate its consumer acceptability and the effect of its consumption on postprandial blood glucose, triglyceride, and satiety responses. In the first instance, the phytochemical composition of the MGTP was determined and compared to green tea extract powder (GTEP), another popular product, which is prepared by solvent extraction. HPLC analysis revealed that MGTP had higher total catechin content and lower caffeine content than GTEP. MGTP was incorporated into shortbread biscuits at 2, 4, 6 g per 100 g of flour. The effect of baking, storage, and the addition of sodium bicarbonate on the catechin stability was evaluated. Percentage of total catechin remaining in biscuits ranged from 81-89% when compared to catechin content in dough. Epimerization of epigallocatechin gallate (EGCG) to gallocatechin gallate (GCG) occurred during baking. Moreover, over one month storage, epigallocatechin (EGC) loss (30-50% loss) was significant and contributed to the significant loss of total catechins. Next, the sensory evaluation of shortbread biscuits formulated with three levels of MGTP (2, 4, 6 g per 100 g of flour) and three levels of sugar (25, 30, 35 g per 100 g of flour) was conducted through acceptability test with a 9-hedonic point scale. The biscuits that contained 2 g of MGTP and 25 g of sugar per 100 g of flour showed the highest acceptability, whereas the biscuit that contained 6 g of MGTP and 25 g of sugar per 100 g of flour received the lowest acceptability. The result indicated that consumers preferred the biscuits with low content of MGTP. Finally, a pilot study investigated the effect of MGTP, either incorporated into shortbread biscuits (6 g per 100 g of flour) or consumed as a drink (3 g dissolved in water) with a plain biscuit, on the postprandial glucose, triglyceride and satiety responses in healthy human subjects. The pilot study revealed that among Asian participants, the triglyceride response after consuming biscuits that incorporated with MGTP was significantly lowered, when compared with plain biscuits and plain biscuit with green tea drink meal. The result shows a possibility that a shortbread biscuits’ matrix may enhance the triglyceride lowering effect of MGTP. Moreover, the sensory evaluation result indicated that familiarity of MGTP could increase the acceptability of shortbread biscuits incorporated with MGTP. Hence, this research shows that biscuits with MGTP has a potential to be put in the healthy food market