Volume 5 • Issue 1 • 1000341 J Nutr Food Sci, an open access journal ISSN: 2155-9600 Open Access Research Article Teklu and Lema, J Nutr Food Sci 2015, 5:1 DOI: 10.4172/2155-9600.1000341 Journal of Nutrition & Food Sciences J o u r n a l o f N u t r i t i o n & Fo o d S c i e n c e s ISSN: 2155-9600 *Corresponding authors: Demeke Teklu, Oromia agricultural research institute, Zeway, Oromia, Ethiopia, Tel: +251913038068; E-mail: demeketeklu@yahoo.com Received November 18, 2014; Accepted December 24, 2014; Published December 29, 2014 Citation: Teklu D, Lema A (2015) Optimization of Time and Temperature for Smoking of Nile Tilapia for a Better Preservation of Protein and Gross Energy Value. J Nutr Food Sci 5: 341. doi:10.4172/2155-9600.1000341 Copyright: © 2015 Teklu D, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Optimization of Time and Temperature for Smoking of Nile Tilapia for a Better Preservation of Protein and Gross Energy Value Demeke Teklu* and Alemu Lema Oromia agricultural research institute, Zeway, Oromia, Ethiopia Abstract This experiment was conducted to optimize temperature and time for hot smoking of Nile Tilapia in order to get the most nutritive quality. Three levels of smoking temperature (80 ± 3°C, 90 ± 3°C and 100 ± 3°C) and time (2:00, 2:30 and 3:00 hours) were used. Accordingly, Face centered central composite design using Design expert (version 7.0.0., Stat-Ease, Minneapolis, MN) was used to optimize and evaluate main effects, interaction effects and quadratic effects of smoking temperature and time on gross energy value and overall sensory acceptability. A Multiple Linear Regressions Analysis (MLRA) was performed to determine all the coeffcients of constant, linear, quadratic and interaction terms using least square minimization to ft the intended model to the collected data. The lack of ft test was used to evaluate the ftness of the generated model using coeffcient of determination (R 2 ). The adequacy of the model was justifed through Analysis of Variance (ANOVA).The result show that all the built polynomial equations were found to be statistically non-signifcant as determined by ANOVA, lack of ft is non- signifcant and the model is less adequate to suffciently describe the experimental data. The numerical optimization using desirability approach of all combination resulted in smoking temperatures and times were found to be optimum to produce good gross energy value and sensory acceptability of smoked fsh. From model summary statistics, a negative predicted R 2 implies the overall/grand mean is a better predictor of gross energy value and overall sensory acceptability than the current model. Accordingly, Nile Tilapia (Oreochromis niloticus) smoked at 80 ± 3°C for 2:00 and 80 ± 3°C for 3:00 hour possessed the highest gross energy value (kcal) for non-dried and pre-dried respectively and fsh smoked at 100 ± 3°C for 2 and 3 hours and 90 ± 3°C for 2 and 3 hours possessed highest overall sensory acceptability for non-dried and pre-dried respectively. Keywords: Nile tilapia; Optimization; Smoking; Temperature; Time Introduction Fish is an important source of food and income to many people in the developing world. Te high moisture content of fsh renders it extremely perishable. It has been estimated that in the high ambient temperatures of the tropics, fsh spoils within 12-20 hours of being caught depending on species and size [1]. As fsh is rich in protein with an amino acid composition very well suited to human dietary requirements comparing favorably with eggs, milk and meat, there shall be appropriate method to preserve those mentioned nutrients. Smoking of fsh have developed over many centuries, largely to suit the prevailing climate and is a good method of drying and preserving fsh where there is no cold facility for fresh fsh handling. Smoke curing of fsh is an ancient traditional method aimed at preserving fsh by exposure to heat and smoke. Te components of wood smoke deposited on fsh are not only imparting good favor and color, but also increases stability due to their bactericidal and antioxidant properties [2]. Te reason for smoking fsh are varied, the process has proved to prolong its shelf life, enhance favor and increase utilization in soups and sauces, reduce wastage times of bumper catches, store for the lean season and increase protein availability to people throughout the year [3]. However, it requires skill and experience to produce a high quality end product that will keep long shelf life as well as high nutrient quality resemble to the natural one. Hot smoking of fsh involves temperature of more than 80 0 C and the fsh is cooked during processing. Excessive heat treatment is known to impair the nutritional value of fsh protein as a result of variety of chemical reactions [4-8] demonstrated that traditionally prepared hot smoking fsh can sufer appreciable protein damage, fnding a loss of lysine availability in traditionally smoked Tilapia nilotica in Uganda. Te exposure of wet fsh to high temperature is the most likely cause of protein damage. Smoking at 85°C lowered lysine availability and net protein utilization (NPU) [8], however heating dry fsh up to 105°C without an appreciable decrease in NPU. Similarly a temperature of 110 o C did not appear to cause any nutritive damage to dry fsh protein concentration (FPC) even afer four hours exposure [9]. Obileye and Spinelli [10] smoke Tilapia afer drying it at 30°C for two hours to moisture content of 40% before hot smoking. Such treatment causes only minor losses (>20%) in lysine availability, and most of this resulted from the initial drying stage rather than subsequent hot smoking. Tus, in dried fsh the protein may be less sensitive to heat damage, but more evidence is required before defnite conclusions can be drawn as to the relationship between the temperature and time of treatment, moisture content of fsh and the degree of protein damage [11]. Smoking is a method of preserving fsh which involves some processes of cooking, drying and preservative value of the smoke [3]. Smoking is a traditional fsh preservation method of considerable economic importance worldwide. Te smoke is produced by the process of incomplete combustion of wood in order to impart characteristic favor and color to the fsh. In addition, smoking increases shelf life of fsh as a result of the combined efect of dehydration, antimicrobial