Quality indices of Jew's mallow and spinach during frozen storage

In this study, Jew's mallow and spinach were heat treated and kept frozen, at -18 degrees C, for 3 months. Analysis of some chemical components and enzymatic activities as well as a sensory evaluation were undertaken. At the end of the storage period, blanched spinach showed no PPO (polyphenyloxidase) activity at all, but still contained PO (peroxydase) and LO (lipoxygenase) activities. The untreated spinach stored under the same conditions showed high activities of PO, PPO and LO. The heat treated mallow still contained high enzyme activities which decreased slowly during frozen storage. Statistical analysis of the chemical composition and the sensory evaluation results indicated that heat treatments of mallow caused significant differences in total solids, pH, chlorophyll a and total chlorophyll, while frozen storage, of samples of the same treatment for 3 months caused no significant differences in moisture, ash, oxalic acid, pH, chlorophyll a and total chlorophyll. No significant differences could be noticed in the overall acceptability between mallow samples mixed with hot water and those mixed with a hot 0.1% MgCO3 solution. Significant differences were found between the heat treated and the untreated mallow. Changes of the chemical composition and the overall acceptability of blanched spinach during frozen storage showed almost the same trend noticed for the Jew's mallow.