Digestibility is part of the sample consumed and not released into the feces. This study discusses about the protein digestibility of tambaqui fish (Colossoma macropomum) at different ages and sizes in vitro. Protein digestibility is the ability of the organisms to break down proteins into simple molecular compounds. At the initial stage, all samples used were dried, then distilled water at pH 8 added, and later the mixture was homogenized for three minutes. After the mixture was homogeneous, enzymes and distilled water were added. Samples were then centrifuged and the absorbance of the sample was measured using absorption spectrophotometry. The results obtained during the observations showed that the digestibility of proteins in the casein showed a value of 100%, small pomfret fish for 28.37%, pomfret fish at 58.42%, and large pomfret fish amount to 88.39%. This shows the larger size of the fish, then the digestibility of protein will be higher. In addition, the lower the pH, the protein digestibility will be higher for hydrolysis of proteins requires an acidic environment of pH conditions.

The study was conducted to obtain an optimal combination of time and temperature of the drying process of indigenous cocktail yeast mold culture using RSM. The cocktail yeast mold culture was dried using an oven. The cocktail cultures contain Penicillium citrinum, Aspergillus niger, Acremonium strictum, and Candida famata, namely AC (Amylolytic Culture). The Response Surface Methods (RSM) with Design-Expert® 7.00 software, namely Mixture design with D-optimal was performed. The drying time was between 24- 48 hrs and the drying temperature was between 40-50oC. The total of 16 formulas of the combination of drying time and temperature for processing the dried cultures were produced by RSM. The response chosen was total viability of mold and yeast, water content, water activity, and pH. The result of optimization and verification was obtained by the model: pH (AC) = -0.058A - 1.56 x 10-003B + 7.13, where A = drying temperature ( oC), B = drying time (hr). The AC optimization was achieved at a combination of drying temperatures and time of 50oC for 48 hrs. Desirability values were 0.729. The optimum formula for AC has viability of total yeast mold of 7.39 x 106 CFU/g, moisture content of 5.62%, aw 0.303, and pH 4.18.

Fish Protein Hydrolysates (FPH) is the mixed products of polypeptide, dipeptides, and amino acid. It can be produced from materials that contained of protein by acid reaction, base reaction or enzymatic hydrolysis. The objectives of this study were to study the production of FPH from fish carp meat at post rigor phase and viscera by enzymatic hydrolysis, to determine the specific activity of papain enzyme, and to determine the solubility of FPH. Capacity of fish hydrolyzing can be identified by analyzing the content of dissolved total nitrogen (NTT) compared with nitrogen total ingredient (NTB) in order to get the value of total soluble nitrogen/total nitrogen material (NTT/NTB). The hydrolysis processes were carried out in 0,26% (w/v) papain, 60 οC for 3 hours. The result showed that the specific activity of papain enzyme was about 3.28 U/mg. Solubility of FPH by comparing NTT/NTB was about 0.29% (fish meat) and 0.40% (fish viscera). Proximate test of protein content of fish meat was 18.34 ± 0.04 (g/100 g); while viscera was about 0.95±0.04 (g/100 g). The result indicated that product waste of fish carp had potential as a major of source of FPH.

Peptones are produced from products with high protein content. Recently, peptone produced from fishery by-products were sought as a source of bacteria substrate. In this study, the enzymatic hydrolysis of peptone production of Yellowstrip scad fish at the end post-rigour phase was optimized. Peptones produced were physicochemically characterised and tested for microbial growth application. Proximate composition, peptone characterisation and amino acid analysis were conducted following AOAC methods. The pH value of the peptones was measured using a pH-meter and the microbial growth was monitored via measuring the optical density (OD) of the cultures. The outcome of the research showed that the best enzymatic hydrolysis was 0.20% (w/v) papain carried out for 6 hours. The results showed that the Yellowstripe scad fish peptones (YSFP) had a high protein level (77.46%) and contained essential amino acids such as histidine (4.12%), isoleucine (0.96%), leucine (2.42%), lysine (2.25%), methionine (3.07%), phenylalanine (1.68%), threonine (1.06%), valine (2.61%), and arginine (2.85%). The end post-rigour phase YSFP has a solubility of 97.08%; total nitrogen of 12.39%; α-amino nitrogen of 1.03 g/100 g; α-amino nitrogen per total nitrogen of 8.31 and salinity of 4.19%. Bacillus spp., Staphylococcus aureus and Escherichia coli was observed to have better growth performances on the YSFP than bacto peptone.

Red tilapia is a good commodity to be developed because it has a high nutritional value composition, with a protein content 17.8%, fat 2.8%, and others composition. The fillet of red tilapia fish is easy to spoil, because of S. aureus, Salmonella sp., and other microbes. Many methods are used to save and preserve the quality of fillet, such fillet preparation through good sanitation practices, cooling process, but the effort were not optimal. The objectives of this study were to 1) evaluate the potency of antibacterial produced by Lactobacillus acidophilus and Bifidobacteria biffidum to inhibit the growth of spoilage bacteria that contaminated the red tilapia fillet; 2) evaluate the effect of antibacterial compounds produced by Lactobacillus acidophilus and Bifidobacteria biffidum of inhibiting the setback fillet quality, 3) determine the shelf life of red tilapia fillet at room temperature. Antibacterial activity test is done by using the well diffusion method; the rate of deterioration of quality of fish tests done by observing the organoleptic parameters, pH measurement test, total volatile base method. Total number of bacteria were performed by Standard Plate Count (SPC) test. The LAB’s are able to inhibit the growth of spoilage bacteria Pseudomonas aeruginosa about 8.67-9.00 mm and Listeria monocytogenes about 8.33-9.00 mm through the well diffusion method. pH values about 5.71-5.74, TVB values about 1,26-21.43 with SPC test about 1.39-4.83 CFU/mL. The antibacterial compounds could inhibit  the rate of deterioration of quality red tilapia fillets until 14 hours.