EFFECT OF PRESERVATION METHODS AND STORAGE ON NUTRITIONAL QUALITY AND SENSORY PROPERTIES LEAFY VEGETABLES CONSUMED IN NIGERIA

Sobowale, S.S^1*, Olatidoye, O.P², Olorode, O.O¹ and Sokeye, O.K³

¹Department of Food Science and Technology, Moshood Abiola polytechnic, Nigeria

²Department of Food Science and Technology, Igbinedion University Okada, Nigeria

³Department of Food Technology, Federal polytechnic, Ilaro, Nigeria.

E-mail: waledoye@yahoo.com

ABSTRACT

In Nigeria, leafy vegetables are preserved by sun-drying and used like freshly harvested vegetables in soups. An experiment to investigate the effect of different drying methods on the nutritional quality and sensory qualities of leafy vegetable (Celosia argentea, fluted pumpkin leaf (Telfaria accidentalis) andwaterleaf (Talinum triangulare) was conducted. The leafy vegetables were washed, shredded, weighed and divided into four equal parts. one part (1kg) was subjected to sun drying for 5 hrs daily for 2 days, while the other three parts(1kg each) was subjected to blanching, cooking and  oven drying at a temperature of 45⁰C until constant was attained. The dried leafy vegetables (sun-dried and oven-dried) were milled into coarse using hand milling machine. Samples (250g each) of fresh (raw), sun-dried, oven-dried, blanched and cooked vegetables were used separately to prepared soup for 5min in soups.  K, Fe, Na, Mg and Ca were the predominant mineral elements analyzed. Sun drying caused significant (P ≤ 0.05) reductions in the K, Na, Ca, Mg, Zn, Fe, and P contents of the vegetables and accounted for 44.8-47.1% loss of vitamin C while oven drying accounted for 36.8–39.6% respectively.   Among the treatments, cooking accounted for 64.3–67.5% loss of vitamin C while blanching and sun drying accounted for 44.8-47.1% and 36.8–39.6% respectively. Panelists rated the soups significantly (P≤ 0.05) higher for colour, taste, texture, flavour and overall acceptability. Fresh fluted pumpkin soup was rated significantly (P≤ 0.05) higher for colour, taste, texture and flavour characteristics, while fresh water leaf vegetable soup was highly rated for taste, flavour and overall acceptability. When compared with other dried vegetable soups, dried water leaf vegetable soup had the highest score for flavour and taste while dried fluted pumpkin soup had the highest score for colour and overall acceptability.  Generally, panelists preferred the fresh to dried vegetable soups.

Keywords: Sun-dried, Oven-dried, Blanching, Cooking, Nutritional quality, sensory properties,                 Leafy-vegetables