Impact of processing on nutritional and functional properties of strawberry

Abstract

The market of processed fruits has grown rapidly in recent decades as a result of changes in consumer preferences and attitudes. Strawberry is one of most preferred fruits to incorporate in milk based products or other derived-products. Strawberry antioxidant capacity is affected by the different post-harvest features, such as processing and storage conditions (e.g., time, temperature). Although reducing quality, these processing conditions are required for safety, quality and economic reasons. In order to assure microbial stability some thermal processing techniques can be applied. These techniques as well storage conditions after processing can affect the phytochemicals composition and nutritional quality of fruit by promoting changes resulting from cell wall and membrane disruption and chemical reactions. Thermal processing of fruits involves heating to temperatures ranging from 50 to 150 ºC, depending on pH of the product and desired shelf-life. Such treatments may cause undesirable biochemical changes that affect the sensory and nutritional quality of the final product. Antioxidants play a key role in the prevention of oxidative stress-related diseases, and the reduction of chronic diseases has been associated to diets rich in plant foods, particularly fruits. Strawberries are a good source of ascorbic acid, anthocyanins and flavonols, and among the fruits, they possess one of the highest antioxidant activities. Among the phytochemicals, phenols, have received a great deal of attention because of their antioxidant activity, which help to neutralise free radicals. Strawberries are a good source of polyphenols such as tannins, ellagic acid and anthocyanins. Thermal treatment is one of the most important factors affecting the stability of phenolic compounds. During processing and subsequent storage, phenolic content and antioxidant activity is changed mainly associated to thermal degradation of anthocyanins, but also due to chemical reactions occurring during storage of processed fruit promoted by temperature but also by other factors such as oxygen present in air, acidity of the medium, presence of enzymes or metals. The aim of this chapter, therefore, is to review the impact of different thermal techniques and associated storage conditions (e.g., time and temperature) of processed strawberry on nutritional and functional characteristics of strawberries, and establish their role on the quality of fruit.