3. Results and discussion
3.1. Ascorbic acid
The effect of storage time on ascorbic acid content is presented in the Fig. 1. Comparison of average ascorbic acid contents at a storage temperature showed significant decreases of 64.5%, 10.7% and 8.9% in ascorbic acid at −12, −18 and −24 °C, respectively (Table 1). The major loss of ascorbic acid occurred during the first 15 days of storage at −12 °C (31.4%). This result confirms those of Ibanez, Foin, Cornillon, and Reid (1996), that showed that the sharpest decrease of ascorbic acid occurred in the first 15 days of storage. The most likely cause for this behaviour is freeze-concentration, i.e., the increase in concentration of solutes that occurs in the unfrozen phase during freezing (Thomson & Fennema, 1971).