Modelling and optimization of the processing of a healthy snack bar made of grape and tomato pomaces

A snack made of 36% by-products of grape and tomato pomaces was developed, also including other ingredients such as oats, chia, quinoa, honey, and peanut butter. The recipe was defined as tasty and healthy by a focus group. The snack was produced by using forced air at three different drying temperatures (50 °C, 60 °C and 70 °C). The Newton, Page, Henderson & Pabis, and Midil-li-Kucuk models fit the drying curves well. The average values for the Newton’s model drying constants were: k50= 2.71x10-1 ± 3x10-3 min-1; k60= 2. 76x10-1 ± 4x10-3 min-1 and k70= 3.91x10-1 ± 8x10-3 min-1; at 50 °C, 60 °C and 70 °C, respectively. The product’s quality was assessed over storage, regarding water activity and texture (hardness, springiness, cohesiveness, chewiness and resilience). The three tested processing temperatures did not influence the final product’s quality differently. Since there are no significant differences between initial and final water activity and texture attributes for any temperature, and they were mainly unaltered over storage, the snack bar was considered stable during this period. This new snack which includes by-products from the food industry reduces food waste and contributes to a circular economy model, simultaneously presenting environmental and economic advantages.