Thuan-Chew Tan

Composition, physicochemical properties and thermal inactivation kinetics of polyphenol oxidase and peroxidase from coconut (Cocos nucifera) water obtained from immature, mature and overly-mature coconut

Composition, physicochemical properties and enzyme inactivation kinetics of coconut water were compared between immature (IMC), mature (MC) and overly-mature coconuts (OMC). Among the samples studied, pH, turbidity and mineral contents for OMC water was the highest, whereas water volume, titratable acidity, total soluble solids and total phenolics content for OMC water were the lowest. Maturity was found to affect sugar contents. Sucrose content was found to increase with maturity, and the reverse trend was observed for fructose and glucose. Enzyme activity assessment showed that polyphenol oxidase (PPO) in all samples was more heat resistant than peroxidase (POD). Compared to IMC and MC, PPO and POD from OMC water showed the lowest thermal resistance, with D83.3°C=243.9s (z=27.9°C), and D83.3°C=129.9s (z=19.5°C), respectively.

Frozen storage stability of beef patties incorporated with extracts from ulam raja leaves (Cosmos caudatus)

In Malaysia, fresh ulam raja leaves (Cosmos caudatus) are eaten raw with rice. In this study, beef patties incorporated with extracts of ulam raja (UREX) and commercial green tea extract (GTE) added individually at 200 and 500 mg/kg were stored at -18°C for up to 10 weeks. Lipid oxidation, cooking yield, physicochemical properties, textural properties, proximate composition and sensory characteristics of the beef patties were compared between those incorporated with UREX, GTE and the control (pure beef patty). Incorporation of UREX or GTE at 500 mg/kg into beef patties reduced the extent of lipid oxidation significantly (P<0.05). UREX showed a strong lipid oxidation inhibitory effect, comparable with GTE. In addition, a significant improvement (P<0.05) in cooking yield and textural properties was also recorded. However, incorporation of UREX and GTE into beef patties showed no significant influence (P>0.05) on the colour, pH, proximate composition and overall sensory acceptability of the patties.

Assessment of the ribose-induced Maillard reaction as a means of gelatine powder identification and quality control

The addition of ribose to bovine or porcine gelatine solutions followed by heating at 95 °C yielded brown solutions with different pH, colour (CIE L(*) and b(*)) and absorbance (A(420*) values. These differences were used for gelatine powder identification, differentiation and quality control. Differentiation analysis of the Maillard reaction parameters was conducted using cluster analysis (CA) and confidence intervals (CI). The potential use of the method as a quality control procedure was evaluated by using statistical process control (SPC). CA revealed that the two types of gelatine could be classified into two different groups. CI (95% confidence) revealed that the absorbance and colour values could be used as indicators for differentiation between the two types of gelatine because the intervals between the Maillard reaction parameters of the samples were far apart. The methodology demonstrated good reproducibility because it behaved predictably based on the X¯-S charts generated from the SPC charts.

Total phenolic content and antioxidant activity of Ulam raja (Cosmos caudatus) and quantification of its selected marker compounds: Effect of extraction

ABSTRACT The effect of heating time (30, 45, and 60 min) and temperature (45, 65, and 85°C) on the extraction yield (total soluble solids) of Ulam raja (Cosmos caudatus) was studied using face-centered composite design-response surface methodology. Total phenolic content and antioxidant activity (TEACDPPH) of samples obtained by aqueous extraction under different temperature and time were determined using Folin–Ciocalteau and 2,2-diphenyl-1-picrylhydrazyl scavenging activity assays, respectively. The yield, total phenolic content, and TEACDPPH of Ulam raja extracts ranged as 3.0–4.2 °Brix, 36.09–37.76 mg gallic acid equivalent/g, and 121.17–146.84 µmol Trolox equivalent/g of plant material on dry basis, respectively. Yield and TEACDPPH of samples were significantly influenced (p < 0.05) by the extraction conditions. Meanwhile, no significant effect (p > 0.05) on total phenolic content was observed. Extraction of Ulam raja at 85°C for 30 min resulted in higher yield and TEACDPPH of the extract. The chromatographic and spectral data confirmed the presence of several flavonoids in the lyophilized Ulam raja extract, i.e., quercitrin, catechin, and rutin, and their quantities were also reported as 36.9, 25.0, and 8.2 mg/g of Ulam raja extract, respectively.

The use of selected hydrocolloids to enhance cooking quality and hardness of zero‐salt noodles

The effects of table salt (TS) and hydrocolloids on water-holding capacity, optimum cooking time, cooking qualities, pH and textural properties of noodles were investigated. TS, xanthan gum (XG), carrageenan (CRG), Arabic gum (AG) and locust bean gum (LBG) were added at 0.5%, 1.0%, 1.5% and 2.0% of flour weight. XG, CRG and LBG contributed to significantly (P < 0.05) higher water-holding capacity of dough and firmer texture, but significantly (P < 0.05) lower cooking loss than zero-salt noodles (ZSNs) and white-salted noodles (WSNs). Hydrocolloids contributed in shorter optimum cooking time than ZSNs. Springiness of noodles was not significantly (P > 0.05) affected by increment of TS and hydrocolloids. TS1.5, ZSN-XG1.5, ZSN-XG2.0 and ZSN-CRG1.5 had significantly (P < 0.05) higher cooking yield than ZSNs. The increment of TS and hydrocolloids had significantly (P < 0.05) increased the pH values of noodles. ZSN-XG2.0, ZSN-CRG1.5 and ZSN-LBG1.5 may be useful to enhance ZSNs due to the better noodles qualities than ZSNs.