where Cvit and Cvito are the concentrations of vitamin C at time
t and zero, respectively, and kvit is the apparent reaction rate
of vitamin C loss. Cvito for frozen strawberry was measuredto be 29.25
±5.18 mg/100 g (average value±standard deviation,number of replicates = 48). According to Eq. (1), values forapparent reaction rates of vitamin C loss, kvit, were calculated
(Table 1). After the freezing process, during the subsequentisothermal frozen storage, strawberries exhibited a significantloss of vitamin C at all temperatures studied (Fig. 1a).
Compared to other published work, the vitamin C content for frozen strawberries in this study showed a better retention.For example, Mallet (1993) measured no retention of vitamin
C (100% loss) after 30 days of storage time at−5 ◦C. In our case,37.6% retention was observed at the same time. The estimated rates of vitamin C loss kvit were lower for the osmotically pretreated samples (OPrT) (Table 1). For all series of samples,it can be deduced that below
−12 ◦C, vitamin C is remarkably stable in the modified matrix of pre-treated samples. For
example, the values of kvit for osmo-dehydrofrozen strawberries with glucose or HDM at storage temperature−16 ◦Cwas approximately 3 times less than the kvit values for conventionally
frozen strawberries (Table 1). The respective kvit values for osmo-dehydrofrozen strawberries with oligofructose at−16 ◦C were lower; 3 times less than kvit values for
osmo-dehydrofrozen strawberries treated with the conventional glucose as well as the non-conventional HDM. The equivalent effect of three different OPrT treatments (Table 1)
was sustained by the Duncan HSD test conducted (a = 0.05),
where the corresponding P value was estimated to be above0.001.