Antioxidant properties of both fresh and convection oven-dried guavas (Psidium guajava L.) were determined. Guava slices of 1.0 cm wide, 3.0 cm long and 0.5cm thick (20 g) were subjected to convection drying at 40°C for 9, 12 and 14 hours, respectively, and their water activity, total phenolic content (TPC) and antioxidant activities were measured. Guavas that had been subjected to drying for 9, 12 and 14 hours were shown to achieve the water activity of 0.36-0.49. Ascorbic Acid Equivalent Antioxidant Capacity (AEAC) of guava was found to decrease for all the drying durations. Convection oven-drying of guava for 12 and 14 hours showed a significant decrease in TPC (p < 0.01) and Ferric Reducing Power Assay (FRP) (p < 0.01). Nine hours of convection oven-drying was shown to retain most of the TPC, AEAC and FRP of guava.
This study aims to determine the effect of tapioca and potato starch added at 3, 6 or 9%w/w
on the physical properties of Spanish mackerel (Scomberomoru guttatus) fish balls. Water
holding capacity, gel strength and four attributes of texture profile analysis, namely hardness,
springiness, cohesiveness and chewiness increased with increasing starch concentration for
both fish balls added with tapioca or potato starch after 6th freeze-thaw cycles. Both tapioca
or potato starch-added samples showed decrease in drip loss and colour with increasing starch
concentration up to 9% (w/w) after 6th freeze-thaw cycles. Drip loss and colour of fish balls
made from the two types of starch decreased with increasing starch concentration. Overall,
gel strength, drip loss, and color of fish balls added with starch showed no significant changes
(p≥0.05) after 6th freeze-thaw cycle. The results suggested that starch plays an important role
in improving freeze-thaw stability of fish balls.