Time and energy reduction on grape dehydration by applying dipping solution on freeze drying process

Abstract

To preserve freshness and nutritional quality of fruits and vegetables is required large energy expenditure due to most storage techniques require low temperatures, making the product diffi cult to transport and store. Purpose: To reduce energy expenditure, dehydration processes are being improving by pretreatments and changing frozen stage. Method: Alkaline emulsion pretreatment was introduced to freeze-drying method to reduce the drying time of grapes and obtain signifi cant energy savings. Results: Dehydration process for untreated fresh grape samples was 22 hours, using industrial freeze-drying equipment. It was obtained a high quality product with range 3 % to 7% of fi nal humidity, without losing natural characteristics and organoleptic properties of the grapes. Conclusions: it was found by modifying standard equipment frozen method, using dry ice (CO 2) and applied coconut oil alkaline emulsion pretreatment, a 54% energy saving. Even more the dehydration process decreased the microbial load in the fruit. A product with low number of microorganisms may be consumed by patients with low defenses as cereals, nutritional bars, salads, yogurts, etc. Finally, if all enterprises involved in this fi eld take into account these fi ndings and improve constantly their process they will stop emitting several kg of CO2 into the atmosphere.

Simulation of a single spherical droplet drying considering shrinking and temperature profiles: first drying stage

“…In general, drying occurs in a convective manner by the effective contact between solid particles (including droplets of suspension) and a low humidity gas which is usually heated. For food materials, moisture must be reduced to less than 10% to avoid microbial growth that can negatively affect the quality of the dried product (Yilmaz et al 2019, González-Toxqui et al 2020. In spray drying -commonly used in the drying of food, dairy products, inorganic chemicals, ceramic powders and nanoparticles -atomization is the most important step that defines the properties of liquid droplets after spraying, resulting in several forms of the dry product from fine powders to granules (Campos et al 2021).…”