Effects of enzyme concentration, temperature, pH and time on the degree of hydrolysis of protein extract from viscera of tuna (Euthynnus affinis) by using alcalase

Protein from viscera of tuna was extracted by using water at ratio of viscera to water of 1:1 (w/v) and freeze-dried. The protein was found to be high in glycine (9.6%), arginine (9.2%), alanine (7.0%), lysine (7.2%) and leucine (7.0%). A study was then carried out to determine the effect of alcalase concentration, temperature, pH and incubation time on degree of hydrolysis (DH) during hydrolysis by using single factor experiment. The hydrolysis of viscera protein extract (VPE) was carried out at concentrations of 1.0, 1.5 and 2.0%. The DH of hydrolysates was significantly (p<0.05) increased when enzyme concentration was increased from 1.0% to 1.5% but became constant at concentration exceeding 1.5%. An enzyme concentration at 1.5% was subsequently used in the study of the effect of the other parameters. It was found that the value of the DH also increased when the temperature was increased from 30 to 40°C. However, the hydrolysis at higher temperature (60°C) produced lower DH. Prolonging the time of incubation from 60 min up to 240 min significantly (p< 0.05) increased the DH. As for pH, there were no significant effects observed

Rheological properties of different degree of pregelatinized rice flour batter

The effect of using rice flour at different degree of gelatinization on rheological properties of a batter system was studied. Rice flour was gelatinized by heated for 20, 40, 60 and 90 min. The treated rice flour was used to prepare batters by stirring it for 2 min. The batter were subjected to determination of apparent viscosity, consistency and flow behavior index and storage modulus G’. The results showed that degree of gelatinization, DG of rice flour increased with the increased heating period up to 60 min. All rice flour batter shown shear thinning behavior since the viscosity decreased with increasing shear rate. The behavior was proven by the value of consistency coefficient, K more than 0 and flow behavior index, n less than 1. Rice flour batter heated in a longer period has higher viscosity and could be attributed by lower water content. The storage modulus, G’ of heated rice flour were lower than G’ of commercial and unheated rice flour. This result was probably because of the lower amylose and protein content in the modified starch pastes

Volatile compounds and lactic acid bacteria in spontaneous fermented sourdough

The aim of this study is to identify the predominating lactic acid bacteria (LAB) in a spontaneous fermented wheat sourdough. At the same time, an investigation towards volatile compounds that were produced was also carried out. Lactobacillus plantarum has been identified as the dominant species of lactobacilli with characters of a facultative heterofermentative strain. The generated volatile compounds that were produced during spontaneous fermentation were isolated by solvent extraction method, analysed by gas chromatography (GC), and identified by mass spectrophotometer (MS). Butyric acid has been found to be the main volatile compound with relative abundance of 6.75% and acetic acid at relative abundance of 3.60%. Esters that were formed at relatively low amount were butyl formate (1.23%) and cis 3 hexenyl propionate (0.05%). Butanol was also found at low amount with relative abundance of 0.60%. The carbohydrate metabolism of Lactobacillus plantarum may contributed to the production of acetic acid in this study via further catabolism activity on lactic acid that was produced. However, butyric acid was not the major product via fermentation by LAB but mostly carried out by the genus Clostridium via carbohydrate metabolism which needs further investigatio

Process development for the production of protein hydrolysate from cockle (Anadara granosa) meat wash water

A study was carried out to determine the process parameters and optimization for the hydrolysis of protein precipitate from cockle (Anadara granosa) meat wash water. Precipitation of the protein in the wash water was done using pH manipulation (pH3-8). The precipitate was hydrolyzed using hydrochloric acid (HCl) and optimized for HCl volume, HCl concentration and hydrolysis time using response surface methodology (RSM) based on a central composite rotatable design. Based on the results, hydrolysis of cockle meat wash water precipitate was carried out by precipitation of the wash water at pH4. Optimum condition for the hydrolysis of 2.0 g of cockle meat wash water precipitate was 25 mL of 1 N HCl for 10 h which resulted in nitrogen content (NC) of 0.7% and degree of hydrolysis (DH) of 55%. NC and DH were significantly influenced only by the hydrolysis time

Kesan fermentasi terhadap ciri fizikokimia dan aktiviti antioksida ekstrak mengkudu (Morinda citrifolia L.)

Penyelidikan ini dijalankan untuk mengkaji kesan fermentasi terhadap ciri fizikokimia dan aktiviti antioksida ekstrak mengkudu. Analisis yang dilakukan adalah untuk menentukan nilai pH, keasidan tertitrat, jumlah pepejal terlarut (°Briks), jumlah kandungan fenolik (TPC) dan kuasa penyingkiran radikal bebas (DPPH) melibatkan fermentasi jangka pendek (0, 1 dan 2 minggu) dan jangka panjang (4, 6, 8, 10 dan 12 minggu). Bagi fermentasi jangka pendek, keputusan kajian menunjukkan nilai pH dan kuasa penyingkiran radikal bebas (DPPH) mengalami penurunan yang signifikan (p<0.05) berbanding ekstrak mengkudu segar. Nilai pH, kandungan fenolik jumlah (TPC) dan kuasa penyingkiran radikal bebas (DPPH) menurun secara signifikan (p<0.05) manakala keasidan tertitrat meningkat secara signifikan (p<0.05) bagi fermentasi jangka panjang. Keputusan kajian ini menunjukkan bahawa pH, keasidan tertitrat, jumlah kandungan fenolik dan aktiviti antioksida ekstrak mengkudu mengalami perubahan yang signifikan semasa fermentasi dijalankan. Hanya jumlah pepejal terlarut menunjukkan perubahan yang tidak signifikan (p<0.05) setelah menjalani fermentasi. Berdasarkan keputusan yang diperoleh, fermentasi buah mengkudu didapati tidak menghasilkan kesan yang positif kepada aktiviti antioksida dan jumlah kandungan fenolik bagi ekstrak buah mengkudu dengan fermentasi menghasilkan pengurangan aktiviti antioksida dan jumlah kandungan fenolik yang ketara