Quality changes of freeze dried catfish surimi and predicting of shelf life
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Indonesian fish consumption rate in 2012 reached 30.17 kg/capita/year, but still lower than Singapore fish consumption levels of 48.1 kg/capita/year, even Malaysia reached the high level of fish consumption up to 56.61 kg/capita/year. Catfish as surimi raw material has a tremendous opportunity to be developed in order to utilize oversized catfish as an alternative efficiency in trade. Catfish easily cultivated and affordable for the grassroots level. Selling price of catfish is determined by its size, because it was adapted to the target market. Catfish with the normal size (7-10 fishes/kg) did not encounter sales problems due to high market demand. The problem faced is marketing catfish that weighs more than the consumption size (oversize) that accounted for 10% in each production cycle. The aforemention problems can occur lossing for farmers due to the many oversized catfish that will not sold. Therefore one of the proposed solutions is utilization of catfish in the manufacture of surimi as intermediate raw materials. Research and study of surimi has evolved, but the major problems are the sustainability and continuity of raw materials. Catfish as a aquaculture commodity is expected to be the solution. Surimi products have increased demand in several countries, including in Asia and Europe region. Further processing of surimi into powder form to be one of the important studies in recent years, surimi drying installations are considered to reduce the cost of freezing during storing and transporting. This study aims to determine the best concentration of NaHCO3 duration of soaking, surimi washing frequency and the best dryoprotectant, to evaluate quality changes of dried surimi and to estimate its shelf life. This research is expected to be useful as an initial step oversized catfish used as raw material for surimi products (intermediate product). This study provides an alternative technology in the manufacture of surimi and surimi industry to increase the potential raw material through using inexpensive types of fish that have not been used optimally. This study is conducted into two step mainly the process on making dried catfish surimi and surimi shelf life estimation. The first step research consisted of defatting process, selecting of surimi washing frequency, determination of dryoprotectant, as well as the comparison of the physicochemical properties of wet surimi and dried surimi. Lipid concentration is a key in the process of deffating, the best determination washing frequency is measured through whiteness value, WHC, gel strength, salt soluble protein content, pH value and sensory parameters (folding test and teeth cutting test) analysis. The second step is determination of the best dryoprotectant, the treatments given are trehalose 6%, carrageenan 2%, and mixture dryoprotectant (4% sorbitol, 4% sucrose and 0.5% phosphate). Some test were performed in order to measure and to find out the best dryoprotectant such as yield, water holding capacity, gel strength, salt soluble proteins, density, rehydration ratio, emulsion and foaming properties and the microstructure. The final step were comparison of fish meat, 8 wet surimi, dried surimi and kamaboko through measuring of SEM (microstruture) testing, yield, proximate, water holding capacity, gel strength, measurement of pH, gel strength and sensory testing (folding test and teeth cutting test). In the last part of the study is to estimate the self life of dried surimi using critical water methode with the Labuza model in determining of dried surimi moisture sorption isotherm (MSI) curve. The result in defatting step shows that soaking in NaHCO3 0.75% for 10 minutes was selected treatment, contained fat of 1.52%. One washing cycle surimi was the best treatment, with the whiteness valuev of 57.21%, water holding capacity of 73.28%, salts soluble protein of 7.17%, pH of 6.69, the gel strength of 482.3 g/cm2, and 4.84 in folding test and 8.26 in cutting test. Determination of best dryoprotectant shows trehalose was chosen treatment for being able to maintain the physicochemical properties of surimi during the drying process. Dried surimi had characteristic of water holding capacity 8.01 mL/g, gel strength 826.3 g/cm2, salt soluble protein 18.98%, density 12.12 g/100 mL, rehydration ration 3.81, emulsion capacity 69.3%, emulsion stability 59.3%, foaming capacity 25.33%, and 9.40% for foaming stability. Microstructure of surimi added by trehalose showed compact tissue than surimi with other dryoprotectant and the tissue consisted no damaged and cloted properly. Dried surimi has deteriorated physical and chemical properties, especially the teeth cutting test and folding test value. Estimation of shelf life of dried surimi, consists of several steps. Initial moisture content of surimi powder ranged from 7-12%. Determined the critical moisture content of the linearity between moiture content and water activity of surimi powder, from the experiment equation y = 4.250x - 4.078 with a value of R² = 0.914 and critical moisture content of the product, with x = 0.80 was equal to 0.2098 gH2O/g solid. Moisture sorption isotherm models of surimi powder produced quite smooth and sigmoid curve. The choosen model was Me = log (log (ln (1/aw)) + 1.893) /-2.209 (Hasley Formula) with a value of MRD 2.31. Shelf life estimation of surimi powder at 70% RH with oriented poly prophlene (OPP), high density polyethylene (HDPE), and retort pouch (PET 12/Aluvo 7/LLDPE 40) packaging were 6.1 months, 4.5 months and 22.6 months, respectively.
- MT - Fisheries