Preservation of kale (brassica oleracea var. Acephala), by lactic fermentation and solar drying

Abstract

The study herein was carried out to assess the effect of lactic fermentation and solar drying in the preservation of kale (Brassica oleraceae var. acephala), which is commonly known as "sukuma wiki". This is a vegetable conventionally consumed by all income bracket earners in the country. The approach was to make the vegetable available all-year-round using a cheap technology, to take advantage of the abundance of the vegetable during the wet season and compensate for its scarcity in the dry season. The study used the conventional method for preservation, namely, blanching followed by drying as the control. The experimental method was adapted from the sauerkraut fermentation in cabbages, followed by solar drying. The fermentation process was monitored In terms of titratable acidity and pH. Other qualitative determinations of the final products from both the experiment and control were: moisture content and nutrient content using beta-carotene and ascorbic acid, plus calcium and iron as indicators. The eating quality was evaluated by sensory tests using trained panelists. The finished products were also studied for their keeping quality under different temperatures and humidity combinations in terms of changes of nutritional indicators, and sensory attributes. The results showed that the fermentation pattern of cabbage and that of kale were similar. Final titratable acidity attained in cabbage, however, was 1.58% lactic acid equivalent compared to 1.2% in kales, which was significantly higher. The final pH of cabbage stabilized at 3.4, from an initial pH of 6.5, while that of kale stabilized at 4.0, from an initial pH of 5.6. Crude protein composition of the kale decreased significantly (p-; 0.05) after fermentation. Total ash also increased significantly after fermentation, mainly due to addition of sodium chloride. During the storage period of six months, the fermented samples were able to retain significantly higher amounts of beta-carotene and ascorbic acid as compared to the blanched samples at 5% significance level. The chlorophyll levels were, however, significantly higher in the blanched samples as compared to the fermented samples at all storage conditions. On performing sensory evaluation, there were detectable differences in flavour and general acceptability, with the fermented sample scoring higher. The results, therefore, showed the possibility of adopting a combination of lactic fermentation and solar drying as a means of preserving kale and coming up with a product of superior quality in terms of taste and better nutrient retention capacities.