Effect of microwave-vacuum drying on the physicochemical properties of a functional tomato snack bar

Tomato is an indispensable ingredient of the Mediterranean diet. Reformulation of traditional Mediterranean products to increase the adherence of consumers is becoming popular. In this study, a tomato snack bar enriched with olive powder and pea protein was developed by using microwave-vacuum drying. Formulations also included tomato powder (TP) and low-methoxylated pectin (LMP) as a structuring agent.

The moisture content of microwave-vacuum-dried samples varied in the range 13.6-19.8% and water activity (a_w ) values were ~0.6. LMP and TP concentrations affected the color of microwave-vacuum-dried samples. However, the color mainly changed in conventionally dried samples due to browning. In microwave-vacuum-dried samples, lycopene content decreased with increasing LMP, but increased with increasing TP. Textural properties of microwave-vacuum-dried snack bars increased with increasing LMP and TP.

Both texture and Fourier transform infrared spectroscopy results indicated that there was a network formation due to the contribution of protein and pectin; however, the type of interaction was highly dependent on the drying mechanism. Nuclear magnetic resonance relaxometry data showed that microwave-vacuum-dried samples had a more uniform water distribution. Besides its time and energy efficiency, microwave-vacuum drying improved the color and textural properties of tomato snack bars compared to conventionally dried ones. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.