Orientador: Prof. Dr. Ricardo Pereira Ribeiro

 Data da Defesa: 21/02/2020


INTRODUCTION: Three genera of the Cichlidae family are prominent in fish farming: Oreochromis (Günther, 1889), Sarotherodon (Rüppell, 1852) and Tilapia (Smith, 1840). According to the FAO (2018), the genus Oreochromis stands out, of which more than 90% of the total produced is represented by the Nile tilapia (Oreochromis niloticus, L.). In 2018, Nile tilapia were the second most exploited species of fish aquaculture worldwide, only behind carp species, totaling 4.5 million metric tons, besides the almost 800 thousand metric tons coming from capture (FAO, 2020). In Brazil, fish farming grew 4.9%, while tilapia production increased 7.96%, representing 57% of the total species produced in 2019, the 4th largest producer in the world. (BFFA, 2020). The state of Paraná in the southern region of Brazil was the second largest producer, with production close to 105 thousand metric tons in 2017, a 19.7% increase compared to the production in 2016. The development of fish hydrolysate started in the 1940s in Canada. This product is used to modify the functional properties of food as a source of small peptides and amino acids or as a supplement in biscuits, hamburgers and nuggets, among others, and it is largely used in animal feed as a protein source. The product can be obtained using three main methods: alkaline, acidic, or enzymatic hydrolysis. The last one is used with proteolytic enzymes to make protein soluble (Silva et al., 2014). With the use of enzymes, the industry can have better control over the final product and its characteristics, such as the type of used enzymes responsible for determining the size of the peptide residues (Bhat et al., 2015).

OBJECTIVES:. Taking into consideration that Nile tilapia are the main aquaculture species produced in Brazil, of which filleting yield is quite low, about 33% (Silva et al., 2014) which generates a large amount of slaughter waste, and aiming at a better industrial utilization of protein content from the slaughtered animals, the objective of this work was to enzymatically obtain a powdered tilapia protein hydrolysate (spray-dried and freeze-dried), as well as to evaluate thermal stability, and to perform a chemical-physical characterization of the final product, seeking to show the processing industry of tilapia, a product alternative, which can be used as a supplement food or nutraceutical. Apply it to food products by checking consumer acceptance. Fish protein added foods were, cereal bar, cheese bread and chocolate flavored cake mix.

MATERIAL AND METHODS: Filleting residues and the MSM were obtained in a tilapia slaughterhouse registered in the Federal Inspection Service, located in the western Paraná. The process consisted of mixing the MSM with water at a 1:1 ratio, followed by adding 1% of the enzyme. It had a hydrolysis time of 120 min, and the enzyme inactivation was at 90 oC for 10 min, followed by centrifugation at 3,000 rpm for 10 min using a benchtop centrifuge. After the enzymatic process, the obtained supernatant material containing the hydrolyzed protein was submitted to two different drying processes: (1) a spray dryer (model LM 1.0, Labmaq, Ribeirão Preto, BRA) with

inlet air at 120 C, a feed rate of 0.5 L h-1 and an inlet air flow of 3.5 m3 min-1 and (2) lyophilization, where the frozen material (at -32 C) was introduced into a vacuum chamber (FreeZone Freeze Dryer System, Labconco, Kansas City, USA), with absolute pressure of less than 0.5 mBar, exchanging heat at 40 C for 36 h. Moisture, ash and crude protein contents were determined according to the procedure described by the AOAC (1990) and the total lipids extracted by the method described by Bligh and Dyer (1959), with some modifications. To determine the amino acid profile, the high-performance liquid chromatography (1290 Infinity UHPLC, Agilent Technologies, Santa Clara, USA). FTIR analyses were conducted using a FT spectrophotometer (model Frontier Spectrum 100, PerkinElmer Inc., Waltham, USA). Differential scanning calorimetry (DTA) and thermogravimetric (TG) analyzes were determined on STA 6000 equipment (Simultaneous Thermal Analyzer, PerkinElmer Inc., Waltham, USA). A brand colorimeter (model CR 400, Konica Minolta®, Chiyoda, JPN) with illuminant D65 and a 10o viewing angle was used to measure the color. The pH measurements were carried out at room temperature using a precision pH meter (model pH21, Hanna® Instruments, Póvoa de Varzim, POR). Water activity (Aw) was evaluated at 25 oC in the Aw determinant (model Aqualab 4TE, Decagon, Pulmann, USA). The hydrolysate powder was evaluated microbiologically for coagulase-positive Staphylococcus (UFC g-1), Salmonella sp. and coliform counts at 45 oC, according Brazilian regulation (Brazil, 2001). Foods had fish protein, cereal bar, cheese bread and chocolate cake mix, these were subjected to microbiological analysis, chemical composition, color, water activity, texture analysis and triangular sensory test.

RESULTS AND DISCUSSION: The analytical results of the chemical composition are presented. It can be verified that the hydrolysis was efficient. The raw material for hydrolysate production contained approximately 12.2% of protein, after washed, pressed and the excessive blood and lipids removed, it increased to 19.99%. The process shows a gain of 38.96% of protein. The increase of the protein content in the washed and pressed sample is due to the partial removal of the lipids, as described by Kristinsson and Rasco (2000). In spray-dried and freeze-dried samples, the protein content obtained was 87.5% and 89.8%, respectively. The lipids remaining in the dry samples and also in the raw material were analyzed, the fatty acid profile was performed, the fatty acids found in higher concentrations were palmitic acid (16:0), oleic acid (18:1, n-9) and linoleic acid (18:2, n-6). The aminogram of the obtained hydrolysates, as well as the MSM used as a raw material to obtain them. An increase in the amino acid contents of the hydrolysates can be verified, except for taurine and phenylalanine. The presence and value of the amino acids in both products indicate that the treatments applied do not affect the quality of the final product. Among the 21 amino acids, 19 were investigated and found in the hydrolysates, and the 9 essential amino acids were also present, ensuring the good nutritional value of the obtained hydrolysate. The protein samples of lyophilized and spraydried hydrolysates showed similar thermal behavior. Both samples presented a mass loss of 26% at 200 oC, and the onset of degradation was observed at 290oC. These results demonstrate that the protein hydrolysates, regardless of the type of drying, presented good thermal stability, and their application may be suggested in the manufacture of products subjected to heat treatments at temperatures below 290oC. The addition of proteins increased the nutritional content of the products, but left as the samples with greater luminosity, that is, more clearly when compared to the control, since there is no variant. The syringe trend analysis incorporates a stronger force in the cereal bars with a fish protein, unlike what happened with the cake and the cheese loaf. Microbiological tests were satisfactory in all cases <10 UFC/g and absense of Salmonella test. In the triangular sensory test only one cereal bar was considered different by the tasters.

CONCLUSIONS: The hydrolysate obtained by enzymatic hydrolysis showed high protein content, and it can be used for the enrichment of food products or as an alternative protein source. The obtained products are a source of all the essential amino acids, and the application of enzymatic hydrolysis is favored from the nutritional and technological point of view. The thermal analysis proved that the powders obtained are stable at high temperatures, initiating the degradation at 290 oC, which allows us to use then in food products that undergo heat treatment. As the amount of waste generated by the fishing industry is high, there is a possibility of production and application of protein hydrolyzate, since of the three elaborated products, two of them did not have their characteristics affected by the addition of protein hydrolyzate and obtained good acceptance by the fishery. consumers, which were the chocolate cake and the cheese bread.

KEYWORDS: fish by-product, hydrolyzation, amino acids, protein structure



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