EFFECT OF GINGER (Zingiber officinale) AND TURMERIC (Curcuma longa) AS NATURAL PRESERVATIVES ON THE PROXIMATE COMPOSITION OF SMOKED-DRIED Clarias gariepinus and Chrysichthys nigrodigitatus PROCESSED WITH RICE HUSK BRIQUETTES

Abstract

Fish is an important source of high-quality protein, essential amino acids, vitamins, and minerals for human
nutrition. However, fish is highly perishable, particularly in tropical environments where high temperatures
accelerate microbial activity and biochemical deterioration. This study evaluated the influence of natural spice
preservatives on the proximate composition of smoked-dried Clarias gariepinus and Chrysichthys nigrodigitatus
processed using rice husk briquettes. Fresh fish samples were treated with ginger (Zingiber officinale), turmeric
(Curcuma longa), a combination of both spices, and an untreated control. Mineral analysis showed increased
calcium, phosphorus, iron, zinc, and potassium in treated samples, while vitamin retention, particularly vitamins
A, D, and E, was higher in spice-treated fish due to the antioxidant activities of curcumin and gingerol compounds.
Fish were immersed in spice solutions (20 g L⁻¹) for 15 minutes prior to smoking in a traditional drum kiln using
rice husk briquettes as fuel. The smoked fish were stored at ambient temperature for three months. Proximate
composition (moisture, crude protein, lipid, and ash) was determined using standard analytical methods. Data
were analyzed using analysis of variance (ANOVA) at a 5% significance level. Results indicated that spice
treatments significantly improved nutrient retention and reduced moisture content during storage (p < 0.05). The
combined ginger–turmeric treatment produced the highest protein retention and the lowest moisture content in
both species. Clarias gariepinus exhibited slightly higher protein content compared with Chrysichthys
nigrodigitatus. The findings demonstrate that natural spices combined with rice husk briquette smoking enhance
the nutritional quality and stability of smoked fish. The adoption of natural preservatives and sustainable biomass
fuels may contribute to improved fish preservation and reduced post-harvest losses in tropical fisheries.