Texture and water activity of dried durian chips
Table 3 shows the texture and water activity of the dried durian chips in each drying treatment. The texture was considered in terms of hardness and crispiness as indicators of quality of the dried durian chips. The crispiness was presented with an umber of peaks and initial slope. A higher number of peaks and initial slopes means more crispiness. The results show that the hardness of the dried durian chips from MWVC and MWHA drying was lower than from the HA drying method,while the number of peaks and initial slopes were higher. High microwave power also helped decrease the hardness and increase the number of peaks and initial slopes in the MWVC and MWHA methods. The texture, however, did not significantly change with the vacuum level between the MWVC and MWHA methods. This is because of the porous structure created in the combined microwave drying and high percentage of void area fraction at high microwave power.
The water activity of the dried durian chips under all experimental conditions was lower than the value of 0.4, which is safe from microbial damage (see Table 3).