Foam-Mat Freeze Drying of Kiwiberry (Actinidia arguta) Pulp: Drying Kinetics, Main Properties and Microstructure

Abstract

Featured Application: Consumers are becoming more conscious of how their eating habits influence their health, and they are more inclined to incorporate fruits and vegetables into their regular meals. In addition, they are exploring for novel raw materials with potential health benefits. Kiwiberry fruits include bioactive components such as vitamin C, carotenoids, chlorophylls, anthocyanins and phenolic acids, which contribute to their antioxidant activity. They also include lots of dietary fiber. However, they are seasonal and have a short shelf life. As a result, it is essential to adopt processing methods that ensure their availability at all times. To do this, they can be processed into a variety of products, including jams, juices, dry snacks and food powders, which can be used as components in a variety of other food and pharmaceutical items. The kiwiberry is an interesting source of bioactive compounds (micronutrients, polyphenols vitamins and pectins) and enzyme actinidine but has limited durability. The aim of this study was to determine the impact of shelf temperature (10 °C, 25 °C and 40 °C) during freeze drying on the foam-mat kiwiberry pulp drying process and the quality of the obtained material based on analyses such as moisture content, water activity, hygroscopicity, solubility, microstructure and spectral measurement using the FTIR method. The use of higher shelf temperatures during freeze drying positively influenced the drying process, reducing its duration by up to 40.7%. The shelf temperature caused changes in the dry matter content (97.2–99.6%), water activity (0.159–0.221), structure and hygroscopic properties (1.41–4.41 g water/100 g d.m.) of the kiwiberry foam mats. Foam-mat drying at 40 °C exhibited a significantly lower water activity, total porosity and hygroscopicity, providing properties favorable for good microbiological and functional stability during storage. Furthermore, this temperature applied during freeze drying resulted in an increase in the solubility of the obtained material, which indicates its possible use in the matrix of other food products.