Hasanah Mohd Ghazali

Enzymatic Transesterification of Palm Olein with Nonspecific and 1,3-Specific Lipases

The enzymatic transesterification of palm olein was conducted in a low-moisture medium with nonspecific and 1,3-specific lipases from microbial sources. The enzymes were first immobilized on Celite, lyophilized for 4 h and then added to a reaction medium that consisted of 10% (wt/vol) palm olein in water-saturated hexane. The catalytic performance of the enzymes was evaluated by determining the changes in triglyceride (TG) composition and concentrations by reverse-phase high-performance liquid chromatography (HPLC) and the formation of free fatty acids by titration. Studies with lipase fromCandida rugosa showed that the degree of hydrolysis was reduced by drying the immobilized preparation and that the best drying time was 4 h. In all cases, the transesterification process resulted in the formation of PPP, a TG initially undetected in the oil, and increases in the concentrations of OOO (1.3–2.1-fold), OOL (1.7–4.5-fold), and OLL (1.7–4.3-fold), where P, O, and L are palmitic, oleic, and linoleic acids, respectively. SOS (where S is stearic acid), another TG not detected in the oil, was synthesized byRhizomucor miehei andPseudomonas lipases, with the latter producing more of this TG. There was a corresponding decrease in the concentrations of POP, PLP, POO, and POL. PPP concentration ranged from 1.9% (w/w) forMucor javanicus lipase to 6.2% (w/w) forPseudomonas lipase after 24 h. The greatest degree and fastest rate of change were caused byPseudomonas lipase, followed by the enzymes fromR. miehei andAspergillus niger. The effects of transesterification and hydrolysis of palm olein by the various lipases resulted in changes in the overall degree of saturation of the triglyceride components. There seems to be no clear correlation between the enzyme positional specificity and the products formed. Possible mechanisms for the formation of PPP, OOL, OLL, OOO, and SOS are discussed.

Physico‐chemical characteristics of roselle (Hibiscus sabdariffa L.)

The physico‐chemical characteristics of roselle from Malaysia were studied. The parameters analysed included size, weight, pH, titratable acidity, soluble solids, anthocyanin contents, organic acids and sugars. Succinic and oxalic acids were the predominant organic acids found in roselle while glucose was the major sugar present. The present study was also conducted to determine and quantify the most biologically effective natural antioxidants present in roselle. Ascorbic acid, β‐carotene and lycopene, were separated, identified and quantified by HPLC. The amounts of ascorbic acid, β‐carotene and lycopene contents were 141.09mg/100g, 1.88mg/100g and 164.34μg/100g, respectively. The individual anthocyanin in roselle was characterised by TLC and HPLC. Delphinidin‐3‐sambubioside and cyanidin‐3‐sambubioside were the main anthocyanin present in roselle.

Naringin content in local citrus fruits.

Abstract The content of bitter component (naringin) from the skin, juice and seed of musk lime, mexican lime, rough lime, pummelo and mandarin orange was determined by the high-performance liquid chromatographic (HPLC) method. Naringin could only be found in pummelo and rough lime but could not be detected in musk lime, mexican lime and mandarin orange. The skin of pummelo contained a higher amount of naringin (3910 μg/g fresh weight) than the juice (220·0 μg/g fresh weight) whereas the amounts of naringin obtained from the skin, juice and seed of rough lime were 517·2 μg/g, 98·4 μg/g and 29·2 μg/g fresh weight, respectively. Sensory analysis further confirmed that the juices extracted from pummelo and rough lime were bitter while those extracted from musk lime, mexican lime and mandarin orange were not bitter. The correlation coefficient (r) for bitterness using both techniques (sensory and HPLC) was 0·97.

Optimisation of ultrasound-assisted extraction of oil from papaya seed by response surface methodology: Oil recovery, radical scavenging antioxidant activity, and oxidation stability

The present study aimed to investigate the effects of ultrasound-assisted extraction (UAE) condition on the yield, antioxidant activity and stability of the oil from papaya seed. The studied ultrasound variables were time, temperature, ultrasound power and solvent to sample ratio. The main goal was to optimise UAE condition providing the highest recovery of papaya seed oil with the most desirable antioxidant activity and stability. The interaction of ultrasound variables had the most and least significant effects on the antioxidant activity and stability, respectively. Ultrasound-assisted extraction provided a relatively high oil recovery (∼ 73%) from papaya seed. The strongest antioxidant activity was achieved by the extraction at the elevated temperature using low solvent to sample ratio. The optimum ultrasound extraction was set at the elevated temperature (62.5 °C) for 38.5 min at high ultrasound power (700 W) using medium solvent to sample ratio (∼ 7:1 v/w). The optimum point was practically validated.

Effect of pH on phosphorylation of sago starch

Sago starch, in a semidry state was phosphorylated with 2% sodium trimetaphosphate (STMP), 5% sodium tripolyphosphate (STPP) singly, and in combination at pH levels between 6 and 11. As the reaction pH was increased from 6 to 11, the degree of phosphorylation was observed to decrease from 0.186 to 0.083% P with STPP, except at pH 9 where the degree of phosphorylation was increased to 0.224% P. In the case of STMP, the degree of phosphorylation increased from 0.066 to 0.119% P as reaction pH was increased from 6 to 10. In the reactions using a mixture of STPP and STMP, the P content decreased from 0.320 to 0.115% when a similar range of pH was employed. At the reaction pH of 9, a starch phosphate obtained using STPP exhibited low hot paste viscosity but high cold paste viscosity and shear stability when cooked at 95°C. Treatment of sago starch with a mixture of STPP and STMP yielded the best starch phosphate at the reaction pH of 9.5 which showed lower hot paste viscosity and much higher cold paste viscosity than that of sago starch phosphates prepared at pH 9 using STPP. Paste clarity measurements of the phosphorylated starches indicated that cross-linking accelerated rapidly above pH 8 with STMP, above pH 9 with STPP, and above pH 6 with a mixture of the two.

Use of enzymatic transesterified palm stearin-sunflower oil blends in the preparation of table margarine formulation

Abstract Palm stearin–sunflower oil (PS:SO) blends, formulated by mixing 40 to 80% palm stearin in increments of 10% (w/w), were subjected to transesterification catalysed by lipases from Pseudomonas sp. and Rhizomucor miehei (Lipozyme 1M 60). The physical properties of the transesterified products were evaluated by slip melting point (SMP), differential scanning calorimetry (DSC), solid fat content (SFC) and X-ray difflaction (XRD) analyses. SMP results indicate that Pseudomonas lipase caused a bigger drop in SMP (33%) in the PS–SO (40:60) blend than the R. miehei -lipase-catalysed reaction blend (13%). The Pseudomonas -catalyzed blends of PS-SO, at 40:60 and 50:50 ratios, showed complete melting at 37 and 40°C, respectively, while the R. miehei -catalyzed PS–SO blend at 40:60 ratio had a residual SFC of 3.9% at 40°C. Pseudomonas lipase also successfully changed the polymorphic form(s) in the unreacted PS–SO mixture from a predominantly β form to a predominantly β ′ form in the transesterified blends. However, no changes in polymorphic forms were observed after transesterification with R. miehei lipase (as against to the unreacted PS–SO blends). These results suggest that the Pseudomonas lipase caused a greater randomization and diversification of fatty acids, particularly palmitic acids, in palm stearin with the unsaturated fatty acids from sunflower oil than did R. miehei lipase. Based on the physical characteristics, the Pseudomonas -catalyzed 40:60 and 50:50 PS:SO blends would be the two most suitable blends to be used as table margarine formulations.

Compositional and thermal analysis of RBD palm oil adulterated with lipase-catalyzed interesterified lard

Abstract A study was conducted to determine the presence of enzymatically-randomized lard (ERLD) as an adulterant in RBD palm oil using three different analytical techniques, namely gas liquid chromatography (GLC), reversed phase high performance liquid chromatography (RP–HPLC) and differential scanning calorimetry (DSC). Lard extracted from the adipose tissues of pig was enzymatically interesterified using non-specific lipase from Pseudomonas sp. Compositional and thermal characteristics of ERLD were compared with those of genuine lard (GLD). RBD palm oil samples, adulterated separately with various levels of GLD and ERLD, were analyzed using GLC, HPLC and DSC. Neither GLC nor HPLC showed any characteristic adulteration peaks to enable RBD palm oil, adulterated with either GLD or ERLD, to be distinguished from those adulterated with chicken fat (CF). However, DSC provided a better means for identification of lard, with a detection limit of 1%.

Mycelium-bound lipase from a locally isolated strain of Aspergillus flavus link: Pattern and factors involved in its production

Aspergillus flavus produces a lipase (EC 3.1.1.3) which is partly bound to the mycelium during growth. The production of the mycelium-bound lipase is concomitant with growth, and declines when growth ceases. Maximum productivity of the enzyme is obtained when the culture is incubated at 30°C, an initial culture pH of 6·5 and with 2% (w/v) each of corn oil and yeast extract as carbon and organic nitrogen source. Yeast extract affects not only the production of lipase but also the secretion of proteases into the culture medium. Production of the latter enzymes, which inactivate the free lipase, is enhanced by adding yeast extract (1–2%, w/v) to the culture medium. However, at 5% (w/v) yeast extract concentration, proteolytic activity is not detected and consequently, the activity of free lipase may easily be measured. Free lipase activity can easily be detected when 0·001 mol dm−3 EDTA is added to the culture medium. The presence of the chelating agent enhances the production and maintains the stability of the extracted mycelium-bound lipase.

Recent advances in food biopeptides: Production, biological functionalities and therapeutic applications

The growing momentum of several common life-style diseases such as myocardial infarction, cardiovascular disorders, stroke, hypertension, diabetes, and atherosclerosis has become a serious global concern. Recent developments in the field of proteomics offering promising solutions to solving such health problems stimulates the uses of biopeptides as one of the therapeutic agents to alleviate disease-related risk factors. Functional peptides are typically produced from protein via enzymatic hydrolysis under in vitro or in vivo conditions using different kinds of proteolytic enzymes. An array of biological activities, including antioxidative, antihypertensive, antidiabetic and immunomodulating has been ascribed to different types of biopeptides derived from various food sources. In fact, biopeptides are nutritionally and functionally important for regulating some physiological functions in the body; however, these are yet to be extensively addressed with regard to their production through advance strategies, mechanisms of action and multiple biological functionalities. This review mainly focuses on recent biotechnological advances that are being made in the field of production in addition to covering the mode of action and biological activities, medicinal health functions and therapeutic applications of biopeptides. State-of-the-art strategies that can ameliorate the efficacy, bioavailability, and functionality of biopeptides along with their future prospects are likewise discussed.

Modelling the effect of water activity and temperature on growth rate and aflatoxin production by two isolates of Aspergillus flavus on paddy.

Aims:  This study was conducted to characterize the growth of and aflatoxin production by Aspergillus flavus on paddy and to develop kinetic models describing the growth rate as a function of water activity (aw) and temperature.