The Effect of Post-Harvest Treatment and Storage Conditions on Vitamin C Content in Two Leafy Parsley Cultivars

Abstract

The objective of the study was to determine the content of vitamin C (L-ascorbic acid) in two leafy parsley (Petroselinum crispum Mill. Fuss) cultivars subjected to different post-harvest treatments. Ascorbic acid (AA), due to its instability, is one of the indicators of leafy vegetable freshness and quality. High content of this compound in vegetables is desired because of its bioactive properties. The cultivars differ in morphology of usable parts: 'Rialto' has flat lamina and 'Petra' triple-curled lamina. The plant material was obtained in 2015 and 2016 from experimental field in Warsaw-Wilanów. The leaves were washed directly after harvest: a) in tap water or b) in tap water with ozone added. Two methods of postharvest storage were applied: A) at the cold store and B) under simulated retail conditions. In the case of cold store method (A), the plants were tied in tufts and stored at the temperature of 0 °C and RH 90 % for 7, 14, 28 days in two variants: 1) in containers, where leaves petioles were immersed in water, and 2) in special bulk modified atmosphere packaging (MAP), dedicated to fresh herbs (Stepac, Israel). In the case of storage under simulated retail conditions (B), the leaves were kept for 48 hours at 10 °C, RH 30-40 % in two variants: 1) tufts wrapped in perforated PE film with petioles immersed in water, and 2) packed to retail MAPs, dedicated to leafy herbs (Stepac, Israel). Concentration of L-ascorbic acid in the leaves was determined spectrophotometrically, with the method based on reaction of Folin's phenol reagent in low pH. Fresh and stored 'Rialto' leaves were characterised by a higher concentration of AA than 'Petra' leaves (110 and 44 mg g -1 f.w., respectively). Significant decrease of AA after ozone treatment was observed only for 'Rialto' directly after harvest. Storage length had significant influence on the content of AA in both cultivars. Decrease of AA content was observed during storage period. Average concentration of AA after 7 days of storage was 85 and 44 mg g -1 f.w. for 'Rialto' and 'Petra', respectively. After 28 days of storage the concentration was 54% lower for 'Rialto' and 36% lower for 'Petra', compared to the initial content. Leaves after simulated retail conditions showed slightly lower AA content than those stored for 7 days in the cold room. Retail MAPs guaranteed significantly higher preservation of AA in both cultivars than wrapping in film with immersing in water. Washing in ozone-added water showed influence only on AA content in 'Rialto' leaves wrapped in film -they showed lower concentration of AA under simulated retail conditions. Our study showed that the content of AA in parsley leaves was cultivar dependent. Ozone treatment did not have negative effect on AA during the storage. Storage duration, rather than packaging methods, plays a key role in preservation of high content of AA. However, method of packaging is important under retail conditions, where temperature is higher and RH is much lower, than at a cold room.