Influence of citric acid – Ca lactate combination
Since pH has a profound effect on anthocyanin stability and color expression and Ca plays a major role in maintaining the texture of strawberries. For achieving high quality frozen strawberries, a combination of 0.4% citric acid with different levels of Ca lactate dips was used for prefreezing treatments. The experimental results are presented in Table 3. Generally, slight differences are observed between citric acid – Ca lactate combination treatments frozen directly and after cooling for overnight. Adhering 0.4% citric acid in Ca lactate dips prefreezing treatments lead to relative improvement in quality indices, where drip loss reduced by 61–132% relative to untreated and by around 12–19% compared to Ca lactate treatments and by around 44–105% for 0.4% citric acid treatment while firmness raised by around 34–69%, 14–18% and 39–64% for untreated, Ca lactate and 0.4% citric acid treatments, respectively. A considerable reduction in browning index was also observed. The retention of both ascorbic acid and anthocyanin content was noticeably increased by 46–57% and 34–37% compared to untreated and by around 25–27% and 21–31% relative to Ca lactate treatments and by around 21–37% and 3–8% for 0.04% citric acid treatment, respectively. In a study on improving quality of home frozen strawberries, Hudson et al. (1975) added calcium lactate, ascorbic acid, citric acid and tartaric acid alone or in combination to a 60 (w/V) sugar syrup held in storage for up to 3 months. Citric acid gave the best color and overall rating whereas calcium lactate and ascorbic acid improved firmness, suggesting that combinations might be best (see Fig. 2).