Associate Professor Minh Nguyen

Barramundi (Lates calcarifer) muscle with brine 2% in Stand-up-retort pouches was treated at different temperatures from 90°C to 120°C at 600¿MPa, 5¿min. Samples retorted with Fo =¿3.38¿min were used as control. Texture attributes such as hardness and springiness of the high pressure thermal sterilized (HPTS) barramundi samples were increased compared to the retorted samples. Color, TBA, and pH values were similar for all treatments, except for a significant increase in pH of samples treated at 90°C, 600¿MPa, 5¿min after 3¿months of storage, indicating microbial spoilage. Textural sensory quality of HPTS products was also better than retorted products. High pressure thermal sterilization (HPTS) at 600¿MPa and 110°C or 120°C for 5¿min resulted in shelf-stable barramundi products. Overall, HTPS could be a feasible option for the production of sterilized fish product with better texture compared to conventional retorted fish product. Practical applications: High pressure and thermal sterilization (HPTS) of food products is emerging as an innovative method with many advantages. HPTS could result in better nutrition and sensory quality of sterilized food products as lower thermal load applied to the product and less unwanted food processing contaminants such as furan are also produced in food products. However, the application of HPTS on food products, especially, seafood products is still in early stage and limited. The result of this study could be used to develop a scale-up process for sterilized barramundi products in the food industry.

Gac (Momordica cochinchinensis) is commercially used for production of Gac oil. Gac pulp, which accounts for 40-50% of fruit weight, is major by-product. This study aimed to optimise extraction conditions including pH, temperature, time, ratio and ultrasonic power for recovery of pectin from Gac pulp, and compare its properties using ultrasound-assisted extraction (UAE) and acidic hot water extraction (AHWE) techniques, the typical advanced and conventional techniques for pectin extraction. Response surface methodology with Box-Behnken design was applied for both techniques. The results showed that pH was the most influential factor. Optimal AHWE conditions were identified at 90°C for 100 min with solvent to sample ratio of 50 mL/g and pH of 1.5, while optimal UAE conditions were 35 min, pH of 1.5, and ultrasonic power of 200 W. The recovery yield of pectin from UAE (53.80% ± 6.04) was significantly higher than that of AHWE (42.97%± 5.08). Pectin obtained from two techniques were low methoxyl pectin (DE < 50%) with good solubility, potent free radical scavenging capacity, and similar structure. As UAE has advantages of short extraction time, more efficient recovery of pectin with better properties, UAE is recommended for recovery of pectin from Gac pulp for further applications.

Gac fruits were evaluated during storage to observe detailed changes in aril quality (lycopene, ß-carotene and oil concentration). The relationships of these qualities with fruit firmness, skin colour and the total soluble solids (TSS) of aril were also explored to identify any potential indicators of aril quality. Mature fruit were manually picked and sorted for size from two field crops in Vietnam and a greenhouse crop in Australia. They were stored in plastic containers at ambient conditions until the fruit was considered unsalable (7 days at 30°C in Vietnam and 21 days at 21°C in Australia). Storage for a week generally improved aril quality in terms of increasing the concentrations of lycopene (up to 4.3 mg g-1 dry weight), ß-carotene (up to 1.5 mg g-1 dry weight) and oil (up to 0.4 g g-1 dry weight) and these were strongly correlated with firmness (lycopene -0.923, ß-carotene -0.754, oil -0.764, p < 0.01) and TSS (lycopene -0.747, ß-carotene -0.664, oil -0.672, p < 0.01). However, quality declined with further storage. Skin colour did not relate well to aril quality but fruit firmness and aril TSS are candidates in the development of simple indices for the quality management of commercial Gac fruit.

The effects of high pressure processing (HPP) on barramundi muscle at 0.1 MPa (control), 150 MPa, 200 MPa, 250 MPa and 300 MPa at 11 ± 2 °C for 3 min were studied before and after immediate blast freezing and storage at -18 °C for up to 18 weeks. Physicochemical measurements including colour, texture profile, drip loss, pH, free fatty acids and thiobarbituric acid (TBA) values were carried out. HPP at 200 MPa significantly increased hardness and delayed lipid oxidation during frozen storage (for up to 18 weeks) without resulting in a cooked appearance of barramundi muscle. However, drip loss of barramundi muscle pressurised at 200 MPa was similar to control samples and during frozen storage. Application of pressures higher than 250 MPa for 3 min resulted in the loss of visual freshness and increased drip loss of barramundi muscle. Thus, application of HPP at an appropriate level (150-200 MPa) before freezing could improve the quality of frozen barramundi muscle.

This study investigated the effects of different storage conditions, temperatures of -20, 10, room temperature (RT), 40 and 63 °C for up to 12 months in the presence or absence of air and light, on the stability of an encapsulated gac (Momordica cochinchinensis) oil powder. A stability trial of the encapsulated oil powder incorporated into yoghurt, pasteurised milk and cake mix stored at 4 ± 0.5 °C and RT for different storage times was also carried out. The results showed that a progressive degradation of colour, ß-carotene and lycopene, and a progressive increase in surface oil content and peroxide value (PV) occurred in the encapsulated powders with increasing storage temperatures and storage times. However, the degradation was much less when the encapsulated powder was stored at low temperature in the absence of air and light. The degradation of ß-carotene and lycopene in all samples during storage fitted a first-order reaction. The sorption curves of the encapsulated powders at 10, 30 and 40 °C were fitted with BET and GAB models. The results also showed that the encapsulated gac oil powder could be successfully incorporated into food products in terms of retention of colour, ß-carotene and lycopene, and low PV.

Summary: Gac (Momordica cochinchinensis Spreng.) is a tropical vine originating from South and South-East Asia. Gac fruit has traditionally been used in Asia to provide red colour for cuisines and enhance visional health. Recently, Gac fruit has emerged as a potential source of carotenoids, especially lycopene and ß-carotene. Carotenoids and other identified bioactives from this fruit including phenolics, flavonoids and trypsin inhibitors are associated with many beneficial bioactivities such as antioxidant, anticancer and provitamin A activities. In addition to the traditional utilisation, commercial products like Gac powder and Gac oil have been manufactured as natural colourants and medicinal supplements. This paper is a review of the scientific literature on the nutritional composition, biological activities and processing of Gac fruit.

The objective of this study was to optimise the spray drying conditions for the encapsulation of Gac oil using response surface methodology. Results indicated that the corresponding response surface model was sufficient to describe and predict encapsulation efficiencies (EEs) in terms of the oil, ß-carotene, lycopene, encapsulation yield (EY), moisture content (MC), water solubility index (WSI) and peroxide value (PV) with R2 of 0.92, 0.91, 0.89, 0.85, 0.89, 0.98 and 0.97, respectively. Under optimal conditions (inlet and outlet temperatures of 154 and 80°C), the response variables including the EEs of the oil, ß-carotene, lycopene, EY, MC, WSI and PV were predicted and validated as 87.22%, 82.76%, 84.29%, 52.78%, 4.90%, 90.29% and 4.06meq/kg, respectively. Furthermore, physicochemical, reconstitution and colour properties of the optimally encapsulated powder were also determined. It was concluded that this powder containing high content of unsaturated fatty acids, ß-carotene and lycopene, and having the attractive red-yellow colour can be used as nutrient supplement and natural food colourant. © 2014 Elsevier B.V.

The objective of this study was to optimize the wall material concentration and the oil load on the encapsulation of Gac oil using spray drying by response surface methodology. Results showed that the quadratic polynomial model was sufficient to describe and predict encapsulation efficiencies in terms of oil, ß-carotene, lycopene, peroxide value (PV), moisture content (MC), and total color difference (¿ E) with R 2 values of 0.96, 0.95, 0.86, 0.89, 0.88, and 0.87, respectively. Under optimum conditions (wall concentration of 29.5 % and oil load of 0.2), the encapsulation efficiencies for oil, ß-carotene, lycopene, PV, MC, and ¿ E were predicted and confirmed as 92 %, 80 %, 74 %, 3.91 meq/kg, 4.14 % and 12.38, respectively. The physical properties of the encapsulated oil powders obtained by different formulations were also determined. It was concluded that the protein-polysaccharide matrix as the wall material was effectively used for spray-drying encapsulation of Gac oil. © 2014 Copyright Taylor and Francis Group, LLC.

The aims of this study were to develop optimal conditions for decaffeination and spray drying procedures to produce decaffeinated and high caffeine powders from green tea (Camellia sinensis). Blanching the tea leaves with water at 100. °C for 4. min at a water-to-tea ratio of 20:1. mL/g removed 83% of the caffeine while retaining 94% of the catechins. The optimal spray drying conditions, which gave the highest yield of green tea powder and the highest concentrations of the naturally occurring epistructured catechins were found to be 180. °C for the inlet temperature and 115. °C for the outlet temperature. Using these optimal conditions, a decaffeinated green tea powder (7 mg/g caffeine) and a high caffeine powder (95. mg/g) were produced. These two green tea powders had excellent physical properties and could be used as instant teas by consumers or utilized in the food, cosmetic and nutraceutical industries. © 2012 Elsevier B.V.

The effects of Gac oil extraction conditions including microwave power, microwave time, steaming time and hydraulic pressure on extraction efficiency (EE), and b-carotene and lycopene contents were studied. It was found that the EE, and b-carotene and lycopene contents could be enhanced by suitable extraction conditions. Microwave drying was found to be better than air drying for pretreatment. Moisture content after drying and steaming between 8% and 11% (wt/wt) were best for pressing. Results showed that the most suitable conditions for Gac oil extraction from 900 g samples were microwave power of 630 W, microwave time of 65 min, steaming time of 20 min and hydraulic pressure of 170 kg/cm2. Under these conditions, the highest EE of 93% was achieved while Gac oil contained the highest content of b-carotene and lycopene at 140 and 414 mg/100 mL, respectively. Crown Copyright © 2012 Published by Elsevier Ltd. All rights reserved.

The effect of l-ascorbic acid (l-AA) on free sulfhydryl concentration (SH) was evaluated in soy-wheat composite dough from 100-500 (g/kg) soy flour substitution for wheat flour. Raw soy flour (RSF) and physically modified soy flours (PMSF1 and PMSF2) were used for the preparation of the composite dough with wheat flour. The two physically modified soy flours were prepared by steam flushing (PMSF2) and water boiling (PMSF1) of raw soy beans before flour preparation. Using a timer, dough blends were manually mixed (at approximately 60 rpm) to dough development time after which, dough was sampled for the estimation of free SH groups. l-AA (0.05% w/w) was mixed with the dough after dough development and the dough was sampled after 1 h of resting the dough. The results showed that l-AA (0.05% w/w) acted as a reducing agent by increasing SH levels in all soy-wheat dough blends (P < 0.05). After 1 h of resting, soy-wheat composite dough without l-AA had lower concentrations of SH than that with l-AA. A positive correlation was shown between soy flour concentrations and SH concentration before and after dough resting. A negative correlation existed between l-AA consumption and SH concentration for RSF-wheat, PMSF1-wheat and PMSF2-wheat doughs. The results indicated that soy flour weakened wheat flour dough by increasing SH concentration and that l-AA could have a synergistic effect on the reduction of gluten proteins and thus weakening the dough. © 2005.

Direct contact membrane distillation (DCMD) was operated at low temperatures from 25 to 40°C to suit the purpose of thermally concentrating sensitive liquid foods, especially fruit juices to high solid content concentrate with most of the quality attributes preserved. A lab scale DCMD unit has been set up at the Centre for Plant and Food Science, University of Western Sydney. Hollow fibre modules (HFM) using five types of fibres of polyvinylidene fluoride (PVDF) and Halar material, with mass transfer areas ranging from 281 to 573 cm2 were employed. Experiments for concentration of glucose solutions from 30 to 60% (w/w) were carried out. Results indicated that not only the operating conditions were important, but also the membrane properties. It was found that Halar fibres were performing 2-3 times better than PVDF fibres in term of removing water from the feed, and 3-4 times better in term of energy saving. Results also showed that an increase of the feed inlet temperature from 25 to 40°C improved the mass flux up to 6 times and energy efficiency (EE) up to 2.5 times depending on the feed concentration. With flux up to 2.88 kg m-2 h-1 for PVDF and 5.83 kg m-2 h-1 for Halar fibres when concentrating 30% glucose solution at 40°C, DCMD appeared to be an attractive concentration technique, when product quality is the priority. However, with EE from as low as 2.1-14.9%, PVDF fibres employed in the study seemed not to be very suitable for DCMD liquid food concentration under low temperature condition. DCMD in Halar fibres with EE up to 45.6% still encounters the challenge of energy and could only be cost competitive to osmotic distillation and evaporative concentration when cheaper energy sources or heat recovery measures are employed. © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

Farinograph and extensograph were used to study the effect of l-ascorbic acid and physical modification of soy flour on rheological properties of soy-wheat composite dough at various ratios up to 50% soy flour. Soy-wheat composite dough made from physically modified soy flour (PMSF) exhibited higher resistance to extension (Rm), greater tolerance to mixing, better mixing stability, higher water uptake and water absorption than the soy-wheat composite dough from raw soy flour (RSF). l-Ascorbic acid at 250 and 500 ppm improved Rm, (P < 0.05) of the dough made from the RSF and PMSF at 50% soy flour substitution for wheat. The same concentration of l-ascorbic acid decreased extensibility of the soy-wheat dough after 135 min of resting in both models (P < 0.05). © 2005 Elsevier Ltd. All rights reserved.

This paper quantifies the characteristics of concentration and temperature polarisations in osmotic distillation of glucose solutions in hollow fibre module using PVDF fibres, being PV375 and PV660 for low and high feed concentration range respectively. Concentration polarisation on the brine side was found to be more severe than on the feed side with concentration differences being up to 3.17% on the brine side and 1.43% on the feed side. Temperature polarisation, however, was more intensive on the brine side for lower feed concentration range, but less intensive when dealing with higher feed concentration. Under the reported experimental conditions, the temperature differences across the membrane were up to 1.53°C in module PV375, and 1.33°C in module PV660. Overall, concentration and temperature polarisations were found to contribute up to 18% to OD flux reduction. © 2004 Elsevier Ltd. All rights reserved.

The water activity (aw) of glucose and calcium chloride solutions in the intermediate concentration range and at temperatures between 20 and 35 °C was determined. It was found that the aw measured at 25 °C was in accordance with previous studies and fitted the Norrish's model well. However, temperature was found to have a more pronounced effect on aw of solutions at higher concentrations. A polynomial equation for hE/R was developed to correlate the effect of temperature on aw for various concentrations of the two solutions as follows: hE/R = -446.52C3 + 349.34C2 - 120.92C for glucose, and hE/R = -9561.7C3 + 2853.8C2 - 422.4C for calcium chloride solution. © 2002 Elsevier Science Ltd. All rights reserved.

Lact. acidophilus and Bifidobacterium were isolated from yoghurt samples. The isolates were tested for their acid and bile salt tolerance under in vitro conditions. The susceptible isolates viz., La.3 (Lact. acidophilus) and Bi. 1 (Bifidobacterium) were encapsulated by using 2% alginate. The encapsulation enhanced the survival of Lact. acidophilus by 15.9% and Bifidobacterium sp. by 16.6%.

Cottage cheese whey has been a problem waste as it is dilute, salty and acidic. The use of nanofiltration has been applied to cottage cheese whey to concentrate its solids content four fold, while removing about three-quarters of the sodium and potassium salts and some acid. This desalted nanoconcentrated whey was found to be quite stable under refrigeration for up to 6 weeks. It could then be considered as a recovered by-product for use as an ingredient in dairy and other food products. A preliminary process economics case study was carried out for a plant producing 30,000 l/day of cottage cheese whey. The capital cost required was estimated as $700,000. The payback period was calculated to be less than 10 months. © 2003 Elsevier Science Ltd. All rights reserved.

Process measurements made in chemical plants often do not satisfy material and energy balances due to random or possibly gross errors in the measuring device readings. Data reconciliation is a method of adjusting process measurements in a weighted least squares sense in order to satisfy the process constraints as well as minimize the difference between the process variable and the measurement of the process variable. Steady state simulation packages equipped with optimization routines can be used effectively to perform data reconciliation and parameter estimation using existing built-in models which automatically satisfy mass and energy balance constraints. The time required to develop a data reconciliation problem can be significantly reduced by using these packages without sacrificing the quality of the results. Data reconciliation was performed on data from a pilot plant Agitated Thin Film Evaporator (ATFE) for concentrating sugar syrup using the AspenPlus simulation system. An AspenPlus simulation of the ATFE was developed using the built-in rigorous heat exchanger model, Heatx, and the rigorous two phase flash model, Flash2. The optimization was carried out using the built-in SQP, (Sequential Quadratic Programme), optimization routine. Data reconciliation improved the fit between the experimental data and the simulation model from between 30% and 98% as well as guaranteeing that the adjusted process measurements satisfy the mass and energy balances. The time required to develop the AspenPlus simulation and data reconciliation was about 1 h whereas a first principles simulation model developed using the programming language such as Fortran or C would take much longer to develop.

Optical and structural properties of melamine-formaldehyde (MF) aerogels have been studied by transmittance spectroscopy. By combining the two-phase model with Rayleigh model, the correlation length of the void phase and the mean particle size of MF aerogels prepared from aqueous melamine-formaldehyde solutions at concentration in weight of 10% and 12%, and pH of 2.3, 2.0, 1.8, and 1.5, were estimated. Correlation of the correlation length, the particle size and the visible integrated transmittance on the concentration and the pH has been established. Optical transparency of the dried MF aerogels depends strongly on the concentration of the precursor and the gelation temperature than the solution pH. © 1998 Elsevier Science B.V. All rights reserved.