Changes of quality and free radical scavenging activity of strawberry and raspberry frozen under different conditions

Abstract

The effects of different freezing methods and long‐term frozen storage on quality of strawberry and raspberry were investigated, that is, the retention of initial property and free radical scavenging (AO) activity after individual quick freezing (IQF) and conventional (discontinuous) freezing. The physicochemical properties, vitamin C, and AO activity were more affected by long‐term frozen storage than by freezing itself; however, their better retention was obtained after IQF. Moreover, AO activity was found to be higher in frozen samples compared to fresh fruits, but significant decrease was detected after 8 months of frozen storage. Despite the significantly higher initial content of vitamin C in strawberry, it demonstrated a lower AO activity than raspberry. Sensory attributes were significantly affected by freezing; the most considerable changes were recorded on their texture/firmness, especially after conventional (slow) freezing. Therefore, IQF can generally be suggested as a more suitable method of preserving these delicate fruits than slow freezing. Practical applications Nowadays, consumers are increasingly interested in foods that possess not only good nutritional value but also health‐promoting property. Berries are known as rich sources of micronutrients and antioxidant compounds, but consumption of fresh strawberry and raspberry fruits may be limited because of seasonal and market availability; therefore, they must be preserved commonly by freezing. Frozen food industry is of crucial importance for developing countries, in which the fast freezing industry is rapidly developed. Investigation of the effect of industrial freezing and frozen storage on retention of the quality‐related property and antioxidant activity is important for providing the best quality for consumers and health benefits, as well as international fruit trade. In addition, the results obtained in this study could provide best practice and guidance for the frozen fruit industry.

Quality Characteristics of Raspberry Fruits from Dormancy Plants and Their Feasibility as Food Ingredients

“…The Versailles fruits seem to be appropriate for conferring acidity and sweetness if used in juices, when compared to the Pacific Deluxe fruits. Despite this variability, the physicochemical parameter values, except for those of the total solids of Pacific Deluxe, were within the range reported for the other R. idaeus species collected at commercial maturity: pH of 2.9 to 4.2, total solids of 5.5 to 12.6 • Brix, titratable acidity of 0.8 to 1.9 of CAE/100 mL of juice, and moisture of 82.0 to 90.3% [12,13,17,[30][31][32]. These results allowed the inference that fruits from the dormancy state have similar physicochemical attributes to those of the commercially available fruits.…”

Nanocellulose as a Novel Cryoprotectant to Improve the Quality of Frozen Sour Cherries

“…Ice crystal formation during freezing can damage cell walls and membranes, causing lower hardness and higher drip loss (Li et al, 2020). Anthocyanin pigments are responsible for the color characteristics of berries, and the color difference in sour cherries was probably due to the replacement of anthocyanin pigments during freezing (Stevanović et al, 2022). This is supported by the fact that there is a significant correlation between color difference and total monomeric anthocyanin content (r = − 0.387).…”

Recent developments in freezing of fruits and vegetables: Striving for controlled ice nucleation and crystallization with enhanced freezing rates

“…Application of individual quick freezing (IQF) (−35°C) and conventional freezing (−28°C) resulted in insignificant changes in the ascorbic acid content of whole strawberries and raspberries. Moreover, a 3.45% increase in the antioxidant activity of the raspberries at −30°C was observed after freezing (Mullen et al., 2002), which may be attributed to freezing associated cellular disruption leading to easier antioxidant extraction after freezing (Stevanović et al., 2022).…”