S. Jinap

Glutamate. Its applications in food and contribution to health

This article reviews application of glutamate in food and its benefits and role as one of the common food ingredients used. Monosodium glutamate is one of the most abundant naturally occurring amino acids which frequently added as a flavor enhancer. It produced a unique taste that cannot be provided by other basic taste (saltiness, sourness, sweetness and bitterness), referred to as a fifth taste (umami). Glutamate serves some functions in the body as well, serving as an energy source for certain tissues and as a substrate for glutathione synthesis. Glutamate has the potential to enhance food intake in older individuals and dietary free glutamate evoked a visceral sensation from the stomach, intestine and portal vein. Small quantities of glutamate used in combination with a reduced amount of table salt during food preparation allow for far less salt to be used during and after cooking. Because glutamate is one of the most intensely studied food ingredients in the food supply and has been found safe, the Joint Expert Committee on Food Additives of the United Nations Food and Agriculture Organization and World Health Organization placed it in the safest category for food additives. Despite a widespread belief that glutamate can elicit asthma, migraine headache and Chinese Restaurant Syndrome (CRS), there are no consistent clinical data to support this claim. In addition, findings from the literature indicate that there is no consistent evidence to suggest that individuals may be uniquely sensitive to glutamate.

Effect of roasting time and temperature on volatile component profiles during nib roasting of cocoa beans (Theobroma cacao)

The e†ect of nib roasting time and temperature on volatile component proÐles was studied using response surface methodology (RSM) which consisted two independent variables : time (5È65 min) and temperature (110È170¡C). A steam distillation extraction (SDE) method was used to extract and gas chromatographÈmass spectrometry equipped with an ICIS data system was used to identify the volatile compounds. Tetramethylpyrazine, trimethylpyrazine, phenethyl acetate, isoamyl acetate, 3-methylbutyl acetate, phenylacetaldehyde, benzaldehyde and 2-phenylethanol were present in all treatments. Pyrazine formation increased as roasting time and temperature were increased. The number of pyrazines increased from 4 to 11 and 25, respectively, when roasting, time was increased from 5 to 35 and 65 min at 140¡C. The unit area of esters increased (up to 1700È1800) when the roasting time was increased from 15 to 65 min (at 110È 120¡C). However, the unit area of carbonyls linearly decreased with an increasing roasting temperature at shorter time (5È25 min). The unit area of phenols was enormously reduced at the highest roasting temperature (160È170¡C) with longest roasting time (45È65 min) while that of alcohol slightly decreased as roasting time and temperature were increased. 1998 SCI. ( J Sci Food Agric 77, 441È448 (1998)

A REVIEW ON MYCOTOXINS IN FOOD AND FEED: MALAYSIA CASE STUDY

 Fungi are distributed worldwide and can be found in various foods and feedstuffs from almost every part of the world. Mycotoxins are secondary metabolites produced by some fungal species and may impose food safety risks to human health. Among all mycotoxins, aflatoxins (AFs), ochratoxin A (OTA), trichothecenes, deoxynivalenol (DON and T-2 toxin), zearalenone (ZEN), and fumonisins (FMN) have received much attention due to high frequency and severe health effects in humans and animals. Malaysia has heavy rainfall throughout the year, high temperatures (28 to 31 °C), and high relative humidity (70% to 80% during wet seasons). Stored crops under such conditions can easily be contaminated by mycotoxin-producing fungi. The most important mycotoxins in Malaysian foods are AFs, OTA, DON, ZEN, and FMN that can be found in peanuts, cereal grains, cocoa beans, and spices. AFs have been reported to occur in several cereal grains, feeds, nuts, and nut products consumed in Malaysia. Spices, oilseeds, milk, eggs, and herbal medicines have been reported to be contaminated with AFs (lower than the Malaysian acceptable level of 35 ng/g for total AFs). OTA, a possible human carcinogen, was reported in cereal grains, nuts, and spices in Malaysian market. ZEN was detected in Malaysian rice, oat, barley, maize meal, and wheat at different levels. DON contamination, although at low levels, was reported in rice, maize, barley, oat, wheat, and wheat-based products in Malaysia. FMN was reported in feed and some cereal grains consumed in Malaysia. Since some food commodities are more susceptible than others to fungal growth and mycotoxin contamination, more stringent prevention and control methods are required.

Simultaneous detection of 12 mycotoxins in cereals using RP-HPLC-PDA-FLD with PHRED and a post-column derivatization system

A new method for the simultaneous quantification of 12 mycotoxins was developed and optimized using reverse phase high performance liquid chromatography (RP-HPLC) with a photodiode array (PDA) and fluorescence detector (FLD), a photochemical reactor for enhanced detection (PHRED) and post-column derivatization. The mycotoxins included aflatoxins (AFB1, AFB2, AFG1, and AFG2), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisins (FB1, FB2, and FB3), T-2 and HT-2 toxins. A double sample extraction with a phosphate-buffered saline solution (PBS) and methanol was used for co-extraction of mycotoxins, and a multifunctional immunoaffinity column was used for cleanup. Optimum conditions for separation of the mycotoxins were obtained to separate 12 mycotoxins in FLD and PDA chromatograms with a high resolution. The method gave recoveries in the range 72–111% when applied to spiked corn samples. The limits of detection (LOD) were 0.025 ng/g for AFB1 and AFG1, 0.012 ng/g for AFB2 and AFG2, 0.2 ng/g for OTA, 1.5 ng/g for ZEA, 6.2 ng/g for FB1, FB3 and HT-2 toxin, 9.4 ng/g for FB2 and T-2 toxin, and 18.7 ng/g for DON. In addition, the limits of quantification (LOQ) ranged from 0.04 ng/g for AFB2 and AFG2 to 62 ng/g for DON. The method was successfully applied to the determination of these mycotoxins in 45 cereal samples obtained from the Malaysian market. The results indicated that the method can be applied for the multi-mycotoxin determination of cereals.

Comparative study of the oxidative and physical stability of liposomal and nanoliposomal polyunsaturated fatty acids prepared with conventional and Mozafari methods

The relative oxidative stability of freshly prepared and stored liposomal and nanoliposomal systems of docosahexaenoic acid (DHA, 22:6 n-3) and eicosapentaenoic acid (EPA, 20:5 n-3) were investigated. The effects of organic solvents on the oxidative stability of liposomal polyunsaturated fatty acids (PUFAs) produced by two methods, the Bangham thin-film hydration (conventional rotary evaporation method and using organic solvents) and Mozafari (direct hydration and without using organic solvents) methods, were compared. The highest physicochemical stability was observed in PUFA liposomes prepared by the Mozafari method, followed by conventional liposomes and bulk PUFAs. There was no significant change in physicochemical stability during 10 months of cold storage (4°C) in the dark. Moreover, the comparison between liposomes (>200 nm) and nanoliposomes (50-200 nm) revealed that the surface charge, physical stability and oxidative stability of liposomal PUFAs increased as the size of the liposomes decreased. The differences in the oxidative stability of PUFAs may be due to the protective effects of aqueous systems, which indicate the advantage of using non-organic solvent (water and CO(2)) techniques in liposome manufacturing.

Validation of the procedure for the simultaneous determination of aflatoxins ochratoxin A and zearalenone in cereals using HPLC-FLD

Method validation for quantitative analysis of aflatoxins (AFs), ochratoxin A (OTA) and zearalenone (ZEA) in cereals using HPLC with fluorescence detector (FLD) is described. Mycotoxins were extracted with methanol : water (80 : 20) and purified with a multifunctional AOZ immunoaffinity column before HPLC analysis. The validation of the analytical method was performed to establish the following parameters: specificity, selectivity, linearity, limits of detection (LOD) and quantification (LOQ), accuracy, precision (within- and between-day variability), stability, robustness, measurement of performance, and measurement of uncertainty. Calibration curves were linear (r > 0.999) over the concentration range, from the LOQ to 26, 40 and 400 ng/g for AFs, OTA and ZEA, respectively. LOD and LOQ were 0.0125 and 0.05 ng/g for aflatoxin B1 (AFB1) and G1 (AFG1), 0.0037 and 0.015 ng/g for aflatoxin B2 (AFB2) and G2 (AFG2), as well as 0.05 and 0.2 ng/g for OTA and 0.5 and 2 ng/g for ZEA, respectively. The mean recovery values were 77–104% for different concentrations of AFs, OTA and ZEA in spiked cereal samples. Both intra- and inter-day accuracy and precision were within acceptable limits. This method was successfully applied for the simultaneous determination of mycotoxins for 60 cereal samples collected from Malaysian markets. Fifty per cent of the cereal samples were contaminated with at least one of these mycotoxins, at a level greater than the LOD. Only one wheat sample and two rice samples were contaminated with levels greater than the European Union regulatory limits for AFs and OTA (4 and 5 ng/g). The means and ranges of mycotoxins obtained for the cereal samples were 0.4 ng/g and 0.01–5.9 ng/g for total AFs; 0.18 ng/g and 0.03–5.3 ng/g for OTA; and 2.8 ng/g and 2.4–73.1 ng/g for ZEA, respectively. The results indicate that the method is suitable for the simultaneous determination of AFs, OTA and ZEA in cereals and is suitable for routine analysis.

Assessment of aflatoxins, ochratoxin A and zearalenone in breakfast cereals

Aflatoxins (AFs), ochratoxin A (OTA) and zearalenone (ZEN) were analysed in 237 breakfast cereal samples collected from central areas of Punjab, Pakistan. According to the results, 41% of the samples were found contaminated with AFs, out of which 16% and 8% samples were found to be above the European Union (EU) maximum content for AFB1 and total AFs, respectively. About 48% samples were found contaminated with OTA and 30% samples were found to be above the EU maximum content. The results have shown that 53% samples of breakfast cereals were found contaminated with ZEN and 8% samples were found to be above the permissible limit of EU. The highest mean level of AFB1 and total AFs were found in semolina i.e. 3.60 and 4.55 μg/kg, respectively. Similarly, semolina was the highest contaminated breakfast cereal for OTA (3.90 μg/kg), while cornflakes (brand B) was found highest contaminated with ZEN (13.45 μg/kg).

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.

Effects of microwave heating on the quality characteristics and thermal properties of RBD palm olein

Abstract In the present work, the influence of microwave power (low-, medium- and high-power settings) and heating time on lipid deterioration produced during the microwave heating of RBD palm olein (RBDPO O ) was evaluated. The changes in thermal profiles by differential scanning calorimetry (DSC) were studied in comparison to the changes in chemical parameters. The DSC method was based on the cooling and melting curves of oils at a scanning rate of 5 °C/min. The chemical evaluation of the oils was based on free fatty acid content, C18:2/C16:0 ratio, peroxide, iodine, and anisidine values. The DSC results were explained on the basis of the endo- or exothermic peak temperatures. A statistical comparative study was carried out on the DSC and chemical parameters. The results indicate that there is a good correlation between the DSC and chemical methods. Based on the results obtained, the DSC appears to be a useful instrumental method in monitoring the oxidation of microwave heated oils, and it may have the potential to replace the time- and chemical-consuming standard chemical methods.

Vicilin-class globulins and their degradation during cocoa fermentation

Cocoa beans were fermented for 144 h using shallow wooden boxes at ambient temperature. Two major polypeptides were found to consist of the storage protein and an albumin fraction. The storage protein comprises two vicilin fractions with molecular weights of 47.1 and 39.2 kDa, and the albumin fraction has a molecular weight of 21.1 kDa. The degradation of vicilin fractions during the course of fermentation was visually detected by sodium docecyl sulphate-polyacrylamide gel electrophoresis. The albumin fraction was found to be the most resistant to proteolysis during fermentation. At the end of fermentation, the 39.2 kDa polypeptide was completely degraded but the 47.1 kDa polypeptide was still present at low intensity. The protein concentrations of 47.1 and 39.2 kDa polypeptides decreased from 1.74 to 0.03 μg and from 0.93 to 0.02 μg, respectively. The protein concentration of 46 and 46.5 kDa polypeptides increased from 0.06 to 0.34 μg and from 0.03 to 0.23 μg, respectively. This could be due to the result of the degradation products of the 47.1 kDa polypeptide.