WITHDRAWN: The effect of different pre-treatments on qualitative properties of freeze-dried Feijoa fruit

Combined Hot Air, Microwave, and Infrared Drying of Hawthorn Fruit: Effects of Ultrasonic Pretreatment on Drying Time, Energy, Qualitative, and Bioactive Compounds' Properties

The present study aimed to examine the effect of ultrasonic pretreatment and hot air, microwave–hot-air, infrared–hot air, and freeze-drying on the drying time, specific energy (SE), qualitative properties (i.e., color, shrinkage, and rehydration ratio), and bioactive compounds’ properties (i.e., antioxidant activity, phenolic, and flavonoid contents) of hawthorn fruit. Drying of hawthorn was conducted from 45 min for the ultrasonic + microwave–hot-air drying to 1280 min for the freeze-drying method. The lowest amount of SE was obtained using the ultrasonic-microwave–hot-air drying method, which was 47.57 MJ/kg. The lowest values in color changes (12.25) and shrinkage (17.21%) were recorded for the freeze-drying method, while the highest amounts for these traits were 45.57% and 66.75% in the HA drying, respectively. In general, the use of different drying methods reduces the antioxidant capacity (AC), total phenolic content (TPC), and total flavonoid content (TFC) during processing compared to fresh samples. The highest values for AC, TPC, TFC, and the rehydration ratio were 30.69%, 73.07 mg-GAE/gdw, 65.93 mg-QE/gdw, and 2.02 for the freeze-drying method, respectively.

The effect of pre-treatment methods on the quality of dehydrated candied Japanese quince fruits during storage

Candied quince is one of the most popular processing products of Japanese quince (Chaenomeles japonica) in Latvia. During the storage of dehydrated fruit, the colour turns darker, thus negatively influence the overall quality and consumers' acceptability of the product. The aim of the present study was to evaluate the effectiveness of different anti-browning agents in combination with fruit blanching and soaking as a type of pre-treatment to preserve the colour of candied quince during 8-months storage. The fruit were harvested at various maturity stage (i.e. unripe, semi ripe and ripe) with the following pre-treatment using three anti-browning agents (l-cysteine, NATRApHASE^®ABAF and Natureseal^® AS1). Hunter L (whiteness/darkness), a (redness/greenness) and b (yellowness/blueness) values were used to measure change in colour. These values were also used for calculation of the total colour change (ΔE*). Considering blanching and soaking as a type of treatment. Best results were obtained with blanching treatment. L* values decreased significantly after dehydration, showing that the samples became darker, during the further 8-months storage, L* values increased, positively influencing the colour of the tested fruit. The data obtained using the Analytic Hierarchy Process Analysis revealed that 0.3% l-cysteine was the best for effective prevention of colour change during long-term storage among the tested agents.