Effect of drying method on the functional properties of some local spices

Abstract

Introduction Spices are a large group of natural ingredients such as dried seeds, fruits, roots, rhizomes, barks, leaves, flowers and other vegetative substances used in a very small quantity as food additives either as color, aroma, flavor or preservative [1]. They are mainly used to improve the palatability/taste and the visual appearance of diets. Most Spices contain phenolic compound that is responsible for their medicinal, antioxidant and preservative properties [2]. The three spices studied include ginger leaf, curry leaf and scent leaf dried using traditional sundried method and oven dried method. The objective of this study is to determine the antioxidant properties of the selected spice. Materials and Method

The spices (ginger, curry and scent leaf) were purchased from a local market in Minna, Niger State. The spices were sundried 5 h daily for 2 consecutive days and turned over at 1 h interval to achieve uniform drying. After sun drying, the sample was milled to powder form. The second sample was oven dried at a temperature of 50ºc for 5 h and turned over periodically to aid uniform drying and milled to powder form. The results obtained from analysis of the antioxidant properties were subjected to one-way ANOVA and the means were separated by Duncan Multiple Range Test using SPSS version 20.

Results and Discussion The result of functional properties of the spices is shown in table 1. The bulk density was in the range of 0.27 to 0.44 g/g. There was no significant difference (p<0.05) in the bulk density of the samples except ginger that shows a variation between the sun dried and oven dried sample.Water absorption capacity ranged from 2.05 to 3.95 g/g. There was significant difference (p<0.05) in the of the ginger and scent leaf except for cury leaf that shows no significant difference between the oven dried and the sundried sample. Oil absorption capacity ranged from 2.45 to 3.95 g/g. There was no significant difference (p<0.05) in the values across the sample. Emulsion capacity was in the range of 46.56 to 55.47 %. No significant difference (p<0.05) observed in the emulsion capacity of the samples. Drying of spices can be done with different method, natural and hot air drying method is widely used [3]. The slight difference recorded between the bulk density of oven dried and sun dried sample could be attributed to variation in drying process. Bulk density is an important functional property that has an implication in packaging and transportation of food materials. Lower bulk density of a given product exhibit better packaging properties than product with high bulk density [4]. The significance difference observed in the water absorption capacity of the samples is in line with the findings of Diaz-maroto [5] who reported changes in the physical, chemical and nutritional properties of spices during drying. Water absorption capacity is the ability of a food material to absorb water [6]. Oil absorption capacity of a product helps the product to retain flavour and improve mouth feel [6]. Some difference observed in the functional properties of the spices shows that method of drying affect the functionality of the spices in the food system. Table 1: Functional properties of the spices Samples BD (g/ml) WAC (g/g) OAC(g/g) EC (%) Scent leaf SD 0.31 ± 0.00cd 3.95 ± 0.07a 3.50 ± 0.00ab 51.02 ± 0.47ab Scent leaf OD 0.32 ± 0.01c 3.50 ± 0.00b 3.55 ± 0.07a 50.00 ± 0.00ab Ginger SD 0.44 ± 0.01a 2.05 ± 0.07e 2.60 ± 0.14c 50.00 ± 00ab Ginger OD 0.37 ± 0.00b 2.55 ± 0.07d 2.45 ± 0.07d 55.47±1.10a Curry leaf SD 0.30 ± 0.00d 2.90 ± 0.14c 3.60 ± 0.00a 46.56 ±0.58c Curry leaf OD 0.27 ± 0.03d 3.00 ± 0.00c 3.50 ± 0.00ab 47.59 ± 0.42c Values are means ± standard deviation of duplicate determination. Values in the same row with different superscript are significantly different (p ≤0.05).

Conclusion

Sun drying and oven drying method are effective in the processing of spices and also affect the functionality of the spices in food system. However, oven dried samples were found to exhibit a better properties in most of the parameter investigated. Therefore, the use of oven drying method in the drying of spices is hereby recommended due to its control temperature of drying and also reduce incidence of contamination of the spices when exposed to open environment for sun drying. Reference 1. Birt, D. A. (2006). Phytochemicals and cancer prevention: from epidemiology to mechanism of action. Journal of the American Dietetic Association 106: 20 – 24. 2. Burt, S. (2004). Essential oils: Their antibacterial properties and potential applications in foods – A review. International Journal of Food Microbiology 94(3): 223–253. 3. Soysal, Y. and Öztekin, S. (2001). Sorption isosteric heat for some medicinal and aromaticplants. Journal of Agricultural Engineering Research, 78, 159-166. 4. Fagbemi T.N. and oshodi A.A. chemical composition and functional properties of full fat fluted pumpkin seed flour (Telferia occidentalis), Nigeria Food Journal , 9,26-(1991). 5. Diaz-Maroto, M. C., Perez-Coello, M. S. and Cabezudo, M. D. (2002). Effect of different drying methods on the volatile components of parsley (Patroselinum crispum L.). European Food Research and Technology, 215, 227230 6. Osundahunsi, O. F., Fagbemi T. N., Kesselman, E. and Shimoni, E. (2003). Comparison of the physicochemical properties and pasting characteristics of flour and starch from red and white sweet potato cultivars. Journal of Agricultural and Food Chemistry, 51:2232– 2236.