Effect of food ingredient on microwave freeze drying of instant vegetable soup

The objective of this work was to study the effect of three different food ingredients viz. NaCl content (1–15 g/100 g water), sucrose content (5–25 g/100 g water) and sodium glutamate content (0.5–10 g/100 g water) on microwave freeze drying (MFD) of instant vegetable soup. Response surface methodology (RSM) was employed to optimize their addition levels in instant vegetable soup for MFD. Finally, a comparison of MFD for instant vegetable soup with and without added ingredients was carried out. The results showed that NaCl content and sucrose content had significant influence on drying time and sensory quality, while sodium glutamate content had insignificant effect. The optimum ingredients of the instant vegetable soup for MFD were: NaCl content of 3.2–5.3 g/100 g water, sucrose content of 2–6.8 g/100 g water and sodium glutamate content of below 4.5 g/100 g water. Comparing with MFD vegetable soup without ingredients, condiments addition could increase drying rate and shorten drying time.