Effect of microwave-vacuum drying on the physicochemical properties of a functional tomato snack bar
Tomato is one of the indispensable ingredients of the Mediterranean diet. Reformulation of traditional Mediterranean products to increase the adherence of the consumers is getting 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 the tomato powder (TP) and low methoxylated pectin (LMP) as a structuring agent.
The moisture content (MC) of the microwave-vacuum-dried samples varied in the range 13.6%-19.8% and water activity (aw) values were ~0.6. The LMP and TP concentration 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 FTIR 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. NMR 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.