Impact of different thermal preservation technologies on the quality of apple-based smoothies

- Smoothies compared to typical juices are rich in soluble and insoluble fiber.
- Addition of juices from valuable fruits can enhance health value of apple products.
- Investigated pasteurization methods are comparable in respect to smoothie quality.

Increased awareness of the importance of health promoting compounds in processed fruit products has led to the creation of novel products, such as smoothies, containing the majority of phenolics and fibre from fruits. It is important to evaluate the impact of traditional and modern thermal preservation methods on the quality of these novel products. Thermal treatment technologies (microwave flow, flow and batch pasteurization) were tested on apple-based smoothies of different composition: apple smoothies containing rosehip juice or wild blueberry juice. Smoothies with rosehip juice exhibited a higher total phenolics content than those with the addition of blueberry juice, but the differences were insignificant. Anthocyanins content measured in the smoothies with blueberry juice strongly depended on the preservation method used; the highest anthocyanins content was found in microwave preserved smoothies. Ascorbic acid content in the juices was the highest in flow-pasteurized juices (29 mg/100 g), while microwave treatment caused a significant decrease (20 mg/100 g). The effect of thermal processing on viscosity was also observed; microwave flow-pasteurized smoothies were characterized by higher viscosity and total pectins than those preserved by the other methods. This suggests that the preservation process interacts with microstructure and can affect smoothie quality during its shelf-life.