Yaakob B. Che Man

Effect of rosemary and sage extracts on frying performance of refined, bleached and deodorized (RBD) palm olein during deep-fat frying

The effects of two natural antioxidants, rosemary and sage extracts, on physico-chemical changes of refined, bleached and deodorized (RBD) palm during deep-fat frying and on sensory acceptability of potato crisps were studied. Results showed that the two antioxidants significantly (P<0.05) retarded the oil deterioration during 6-day frying. The two antioxidants were proven to lower the rate of oxidation of oils during frying. It was also shown that, during frying, the quality of oils gradually decreased. Sensory evaluation indicated that, except for crispiness scores, both rosemary and sage extracts could improve acceptability of fried potato crisps. However, no sample was unacceptable by panellists even up to day 6. In general, sage extract was as effective as rosemary extract in maintaining the quality of oils during frying.

Effects of isolation technique and conditions on the extractability, physicochemical and functional properties of pigeonpea (Cajanus cajan) and cowpea (Vigna unguiculata) protein isolates. I. Physicochemical properties

Physicochemical properties of pigeonpea and cowpea protein isolates were determined as a function of extraction technique and pH of the extracting medium. Protein extractability by the isoelectric point precipitation (IP) technique was positively correlated within the pH of the NaOH solution used in the pH range 8.5–12.5. The micellization (MP) technique extracted significantly (P<0.05) less protein than the IP technique when extraction pH of the NaOH was 9.5 or higher, and 10.5 or higher from cowpea and pigeonpea, respectively. The subunit composition and electrical mobility of the isolates were not affected by extraction technique and pH conditions. However, it was observed that the IP isolate extracted at pH 12.5 had the lowest proportion of hydrophilic amino acids, suggesting that the pH of the extracting medium exerted a major influence on the hydrophilicity of the isolates. Pigeonpea MP isolate exhibited significantly (P<0.05) higher exposed hydrophobicity than the IP isolates except for those extracted at pH 9.5 and 10.5. However, the cowpea MP isolate exhibited significantly lower exposed hydrophobicity than the IP isolate extracted at pH 8.5 but this was higher than the rest of the IP isolates. For IP isolates, an inverse relationship was apparent between the extraction pH and hydrophobicity. The MP isolates from both legume seeds were significantly lighter in colour than the corresponding IP isolates and, for the latter, the lightness value (L) was inversely correlated with extraction pH. Differential scanning calorimetry showed that the MP isolates exhibited higher transition enthalpy (ΔH) than the IP. For the IP isolates, ΔH decreased with increasing extraction pH.

Halal authenticity issues in meat and meat products.

In the recent years, Muslims have become increasingly concerned about the meat they eat. Proper product description is very crucial for consumers to make informed choices and to ensure fair trade, particularly in the ever growing halal food market. Globally, Muslim consumers are concerned about a number of issues concerning meat and meat products such as pork substitution, undeclared blood plasma, use of prohibited ingredients, pork intestine casings and non-halal methods of slaughter. Analytical techniques which are appropriate and specific have been developed to deal with particular issues. The most suitable technique for any particular sample is often determined by the nature of the sample itself. This paper sets out to identify what makes meat halal, highlight the halal authenticity issues that occur in meat and meat products and provide an overview of the possible analytical methods for halal authentication of meat and meat products.

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.

The use of Fourier transform mid infrared (FT-MIR) spectroscopy for detection and quantification of adulteration in virgin coconut oil

Currently, the authentication of virgin coconut oil (VCO) has become very important due to the possible adulteration of VCO with cheaper plant oils such as corn (CO) and sunflower (SFO) oils. Methods involving Fourier transform mid infrared (FT-MIR) spectroscopy combined with chemometrics techniques (partial least square (PLS) and discriminant analysis (DA)) were developed for quantification and classification of CO and SFO in VCO. MIR spectra of oil samples were recorded at frequency regions of 4000-650cm-1 on horizontal attenuated total reflectance (HATR) attachment of FTIR. DA can successfully classify VCO and that adulterated with CO and SFO using 10 principal components. Furthermore, PLS model correlates the actual and FTIR estimated values of oil adulterants (CO and SFO) with coefficient of determination (R2) of 0.999.

Use of natural antioxidants in refined palm olein during repeated deep-fat frying

An optimization study on the use of oleoresin rosemary extract, sage extract and citric acid added into refined, bleached and deodorized (RBD) palm olein before deep-fat frying of potato chips was performed using a constrained mixture design. Results revealed that the use of these natural antioxidants could improve the sensory acceptability of potato chips during a 5-day repeated deep-fat frying. All three antioxidants significantly (P<0.05) improved the sensory characteristics, including appearance, taste, crispiness, odor and overall acceptability. After day 5 of frying, the most acceptable fried potato chips were those fried in oil containing a combination of 0.059% oleoresin rosemary extract, 0.063% sage extract and 0.028% citric acid. The natural antioxidants significantly (P<0.05) lowered the rate of oxidation of oil during deep-fat frying and contributed to measured sensory acceptability of fried potato chips.

Influence of altered solvent environment on the functionality of pigeonpea (Cajanus cajan) and cowpea (Vigna unguiculata) protein isolates

Functional properties of pigeonpea and cowpea isolates were determined as a function of pH and NaCl concentrations. At low pH, nitrogen solubility decreased with increasing NaCl concentration whereas, at high pH, it increased. Addition of NaCl to the solvent medium resulted in a marginal improvement and a significant improvement, in the emulsifying activity and emulsion stability of pigeonpea isolate, respectively. The above treatment decreased these properties for the cowpea isolate. Varying both the pH and NaCl concentrations resulted in significant improvements in the emulsifying properties of the isolates relative to the control treatment. NaCl concentrations higher than 0.1 M significantly (P<0.05) increased the expansion of pigeon and cowpea protein–stabilized foams but reduced foam stability, and adjusting pH from 2 to 8 improved foam expansion but decreased foam stability. Varying both the pH and salt concentration had similar effects on the foaming properties of the isolates. The least gelation concentration (LGC) of the isolates decreased with increasing salt concentration. Adjusting the pH to values away from the apparent isoelectric point, elicited similar responses in LGC. In 0.5 M NaCl solution, adjusting the pH to 2, 6 and 8 resulted in significant reductions in LGC relative to the distilled water protein suspensions.

FTIR spectroscopy combined with chemometrics for analysis of lard adulteration in some vegetable oils

This study was aimed to develop a fast technique of Fourier transform infrared (FTIR) spectroscopy for detection and quantification of lard adulteration in some vegetable oils, namely canola oil (Ca‒O), corn oil (CO), extra virgin olive oil (EVOO), soybean oil (SO), and sunflower oil (SFO). The FTIR spectra associated with Ca‒O, CO, EVOO, SO, and SFO as well as their blends with lard were scanned, interpreted, and identified. The chemometrics of partial least square (PLS) and discriminant analysis (DA) at fingerprint regions of 1500–1000 cm−1 was used for quantifying and classifying of lard in the mixture with vegetable oils, respectively. PLS calibration can be successfully used for quantification of lard in the mixture with vegetable oils, either using normal spectra or its first derivatives. Furthermore, DA based on Mahalanobis distance can classify lard in vegetable oils. El objetivo de este estudio fue desarrollar una técnica rápida de espectroscopia de infrarrojos por transformada Fourier (FTIR) para la detección y cuantificación de adulteración con grasa de cerdo de algunos aceites vegetales, principalmente aceite de colza (Ca‒o), aceite de maíz (CO), aceite de oliva virgen extra (EVOO), aceite de soja (SO) y aceite de girasol (SFO). El espectrograma FTIR asociado con Ca‒O, CO, EVOO, SO y SFO, así como sus mezclas con grasa de cerdo, fueron escaneadas, interpretadas e identificadas. El análisis quimiométrico de mínimos cuadrados parciales (PLS) y análisis discriminantes (DA) en la región de 1500–1000 cm−1 se usaron para cuantificar y clasificar la grasa de cerdo en la mezcla con aceites vegetales, respectivamente. La calibración PLS puede ser usada satisfactoriamente para la cuantificación de grasa de cerdo en la mezcla con aceites vegetales, bien usando un espectro normal o sus primeras derivadas. Además, DA basados en la distancia Mahalanobis pueden clasificar la grasa de cerdo en aceites vegetales.

Substrate preference of mycelium-bound lipase from a strain of Aspergillus Flavus Link

Aspergillus flavus mycelium-bound lipase demonstrates high preference towards short chain triacylglycerols and discriminates against triunsaturated triacylglycerols e.g. triolein. The great discriminating power of its lipase against triolein was shown in comparison with its ability to catalyse the hydrolysis of shorter chain triacylglycerols e.g. tricaprin and less was shown when hydrolysing tripalmitin. A similar phenomenon was noted when the mycelium-bound lipase was used to catalyse the reaction of coconut oil with palmitic acid or oleic acid in n-hexane. The relative percentages of octanoic acid and decanoic acid of coconut oil remaining after 20 h reaction were much less than those of the medium, long and unsaturated chain fatty acids suggesting that short chain fatty acids are preferred. The lipase hydrolyses coconut oil faster than palm olein followed by corn oil, rapeseed oil, soy bean oil and cottonseed oil. This indicates that A. flavus lipase has preference for oils containing saturated fatty acids rather than unsaturated fatty acids.

Differential scanning calorimetry: gelatinisation of sago starch in the presence of sucrose and sodium chloride

The effect of sucrose and sodium chloride (NaCl) on sago starch gelatinisation was investigated by differential scanning calorimetry (DSC). The gelatinisation of starch in the presence of low levels of water and high levels of sucrose was studied. The gelatinisation temperature was found to increase in the presence of sucrose, whereas the gelatinisation enthalpy was unaffected. The gelatinisation temperature range was not as broad in the presence of sucrose as without sucrose. Furthermore, the shape of the gelatinisation endotherm was changed by the addition of sucrose. The double endotherm obtained in limited water–starch systems was changed into a single endotherm, similar to the endotherm obtained in excess water–starch systems at higher temperature. DSC was also used to examine the effects of water and NaCl content on the phase transitions of sago starch. Samples were adjusted to starch–water weight ratios of 2:3 and 3:2 in NaCl concentrations from 1 to 5 M. The gelatinisation temperature of sago starch increased and then decreased as the NaCl concentration increased. NaCl created similar effects on the endotherms with excess water content and on the first endotherm with limited water content. © 1999 Society of Chemical Industry