Published: 2015-11-30

Agro-ecological dynamics in the coastal areas of the vi-etnamese Mekong Delta in the context of climate change (A case study in Bac Lieu province)

Van Pham Dang Tri, Phan Hoang Vu, Pham Thanh Vu, Nguyen Hieu Trung
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Agro-ecological zoning is considered to be a suitable base for agricultural land use planning to especially meet local natural resources and socio-economic settings. The aim of this study was to evaluate historical trend (from 2000 to 2010) and predict changes in the agro-ecological zones of the Bac Lieu province in the context of sea level rise (+17cm) in combination with historical records of upstream discharge (since 1998). The Participatory Rural Appraisal approach and household interviews were used to collect primary along with secondary data collected at different governmental departments and the numerical modelling results. The results showed that existing agro-ecological zones were well-reflected by the existing farming systems in the study area. The defined agro-ecological zones of Bac Lieu province in the future would include stable freshwater areas and changing brackish and saline-influenced areas according to the changes of upstream discharge.

Livestock production systems adapting to the global cri-ses in tropical developing countries - a review

Nguyen Van Thu
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Food crisis has caused recently severe problems in many countries of the world due to an increasing human population and worsening economic development, and global climate change has made these problems even more serious. Large-scale animal production systems have been established in tropical developing countries to satisfy the animal protein demands of human nutrition (e.g., industrial chicken and pork, feedlot beef cattle, concentrate feeding of dairy cattle), but have caused unacceptable harm to the environment (e.g., high levels of nitrogen and phosphorus entering rivers, and greenhouse gas emissions). As the human population increases, there is a greater risk of protein malnutrition, as well as the risk of environmental pollution resulting from natural disasters. Consequently, the reorientation of animal production systems has become a pressing and high-priority issue in tropical developing countries. In many parts of the world, there are currently constraints on livestock production; however, promising and sustainable models of animal production exist that are based on the utilization of renewable plant biomass as feed for livestock production, while saving grains for human consumption. In addition, diversification of the animal species farmed aids in mitigating greenhouse gas emissions, while adapting to climate change. Utilization of animal production models based on appropriately sustainable farming systems ensures the better use of locally available feeds, while increasing renewable energy production. The sensible selection of livestock production models for sustainable development in tropical developing countries could be beneficial for many producers and for our planet in term of socio-economics and the environment.

The effects of probiotic supplementation on growth performance of weaning pigs in the Mekong Delta of Vietnam

Le Thi Men
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The experiment was conducted at the farm in Cho Lach district, Ben Tre province to assess the supply of probiotic products on performance of [Duroc x (Yorkshire-Landrace) - DYL] 108 piglets (12 herds) after weaning. Piglets were weaned at 28 days of age and the experimental period was lasted 5 weeks. The initial live weight of pigs was about 8 kg and final live weight of 26 kg. The experimental design was 3 treatments and 12 blocks (12 herds); each herd was divided into 3 groups randomly allocated into 3 treatments. It included 2 treatments supplied probiotic products (PRO: containing Bacillussubtilis, Lactobacillus spp; PRO-ANT: PRO + neomycine sulphate) vs to the CONTROL (none supply bio-product). Results showed that live weight of pig and growth parameters (weight gain, average daily gain) of pigs which supplied bio-products were significantly (P

Preparation of fungal alcoholic starter using rice malt as substrate

Huynh Xuan Phong, Nguyen Minh Doi, Ngo Thi Phuong Dung
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In this study, rice malt was used as the substrate to culture Saccharomyces cerevisiae for the preparation of defined fungal alcoholic starter. Defined mould starter using Amylomyces rouxii was prepared on the substrate of maize powder and rice husk. The different ratios of rice powder and rice malt were examined: A1 (rice malt only), A2 (1:0.5), A3 (1:1), A4 (1:2), and A5 (1:3). The results showed that the treatment of only rice malt gave the highest ethanol concentration (11.30% v/v) and the yeast population at 8.13 log CFU/g. The mould starter (8.74 log CFU/g) was added into the yeast starter at different ratios (0.5%, 1.0%, 1.5% and 2.0% w/w) for testing the fermentation capacity. Maximum ethanol concentration was 13.67% v/v when the defined fungal starter supplemented with 1% of mould starter and the incubation time for solid-state fermentation was 2 days, and 4 days for alcoholic fermentation stage. The yield of pilot-scale production (8 kg of rice) was found at 1.23 liters of rice white distilled spirit (ethanol concentration was 30% v/v) per one kilogram of rice. Aldehyde concentration of final distilled product was 33.8 mg/L and the quality score was obtained at 14.2/20 by sensory evaluation. This research was indicated the promising application of defined fungal alcoholic starter in local rice white distilled spirit manufactures.

The effect of preparation conditions on the properties of gelatin film from horse mackerel (Trachurus japonicus) scale

Le Thi Minh Thuy, NGUYEN TAN DAT, Nguyen Do Quynh, Kazufumi Osako
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The effects of protein and glycerol concentrations on properties of gelatin film from horse mackerel (Trachurus japonicus) scale were studied. Increasing protein concentration leaded to increasing mechanical properties of gelatin film, while tensile strength (TS) decreased and elongation at break (EAB) increased with increase of glycerol content. Horse mackerel scale gelatin film showed the greatly lower water vapor permeability (WVP) comparable with that of mammalian, cold- and warm-water fish, possibly due to its containing a higher level of hydrophobic amino acid content. Gelatin films from different preparation conditions showed excellent UV barrier properties at wavelength of 200 nm, although the films were transparent at visible wavelength. It appeared that gelatin film derived from horse mackerel scale can be applied as food packaging material due to its low WVP value and excellent UV barrier properties.

FPGA implementation of lifting scheme daubechies discrete wavelet transform for real-time signal compression

Truong Phong Tuyen
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In recent years, rapid development of multimedia applications leads to the requirement of huge data storage and high-speed data transfer capacity so that data compression emerges as an attractive topic. However, it is hard to compress sudden-changing signals, especially in high-speed and real-time processing. This paper proposes a hardware solution for real-time signal compression based on Daubechies wavelet transform (Db WT). The set of Db WT factors has been modified into integer number in order to be suitable for hardware implementation. The experiments were conducted on FPGA prototype implementation of real-time speech compression for evaluating the proposed approach.

The relationship of bitumen content, aggregate surface area, and extraction time using asphalt ignition furnace

Tran Trang Nhat
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Aggregates make up between 80% and 90% of total volume or 94% to 95% of the mass of hot mix asphalt (HMA). For this reason, aggregate properties are very important. It directly affects the workability of the HMA. One of the properties of aggregate is coated surface area.  The main objective of this study was to search the relationship of the surface area of aggregate, bitumen content, and extraction time in order to find the coated surface area of aggregate to be correlative with the optimum bitumen content. Three types of aggregate grading including dense grading, open grading, and gap grading that designed as ACW14, PA, and SMA14 were tested in accordance with the JKR Specification. A total of 45 specimens were prepared using Marshall Mix design method with three types of grading: ACW14 (dense graded), SMA14 (gap graded), and PA (open graded) in order to determine the optimum bitumen content (OBC). The second phase was to determine the coated surface area of aggregate by using the surface area factor. 45 samples were prepared and subjected to extraction of the bitumen content using NCAT ignition furnace to determine the time to remove bitumen from the aggregate in different types of mixes. Based on the results, it was observed that the bitumen content was significantly affected by the aggregate surface area while the aggregate surface area was influenced by the fine aggregate. Moreover, all of the observed parameters fitted highly to the linear relationship. Thus, it can be concluded that the bitumen content, aggregate surface area and the characteristics of bitumen have an influence on the extraction time.

Vulnerability assessment in the coastal plain of the Vietnamese Mekong Delta

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The coastal plain is considered to be one of the most vulnerable areas in the Vietnamese Mekong Delta due to negative impacts of surface water resources changes driven by regional and local climate change and sea level rise. In addition, the vulnerability is also exaggerated due to low adaptive capacity of local residents. In this study, components of vulnerability index (including exposure, sensitivity and adaptive capacity of local residents under negative impacts of both flood and saline intrusion) are calculated in details according to actual conditions of the study area. High vulnerability index would be shifted from coastal areas (at the time being) to zones further inland and along the main rivers (in the future) as local residents were not well-prepared for physical changes. Furthermore, sensitivity analysis was done to understand the reliability of assigned weight for each parameter. 

Lecturers’ perceptions about employing critical thinking in educating geography pedagogy students at Can Tho University, Vietnam

Trinh Chi Tham
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This study investigates the lecturers’ perceptions about employing critical thinking in educating geography pedagogy students at Cantho University (CTU), Vietnam due to interviewing seven lecturers. The study findings have shown that the participants had very positive perceptions about employing critical thinking in educating the geography pedagogy students at CTU and these perceptions related to culture and tradition, teaching and learning habits, the student ability of solving problem, the interaction between the lecturers and students and amongst the students, the collaboration and cooperation among the students, the teacher preparation and supports, and the university/school facilities. In addition, the results of this study have also reported the lecturers’ feedback or solutions on how to employ critical thinking in educating the geography pedagogy learners better. Due to the participants’ perceptions and the feedback that they have made, it seemed that their most concern was around cultural and traditional values in the Vietnamese education system.

An investigation into the levels of feedback and reflec-tion during pre-service teachers’ micro-teaching practices

Vo Huy Binh, Nguyen Thi Hong Nam
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Both feedback and reflection were well-investigated in many studies available in literature; however, the relationship between the two, especially that in micro-teaching practices of pre-service teachers (PreTs) has remained underexplored. This paper reports the results of an investigation into the levels of feedback and reflection during micro-teaching practices.  Five subject-specific teacher educators (TEds) and PreTs at a university of teacher education, in the Mekong Delta participated in the study. Research instruments included observation and interviews. Data of minutes of micro-teaching observation and interviews was qualitatively analyzed. The research indicated two findings: (1) feedback mostly given by TEds supported the reflective process of PreTs and both primarily focused on teaching method-related issues; (2) reflective thinking generated by PreTs was limited at technical level and descriptive in general. The research contributed to bridging the gap in knowledge about the correlation between feedback and reflection and suggesting an urging need of fostering reflective capacity for PreTs based on broader and deeper focuses of feedback used during post-lesson discussions. 

Effect of different drying methods on total lipid and fatty acid profiles of dried Artemia francis-cana biomass

Nguyen Van Hoa, Nguyen Thi Ngoc Anh, Nguyen Thuan Nhi
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Frozen Artemia biomass were dehydrated by outdoor sun drying and three indoor drying techniques which consisted of convective hot air drying (HA), intermittent microwave combined with convective hot air drying (MWHA) and oven drying at temperatures of 50, 60 and 70°C. The aim of this study is to evaluate the effect of different drying techniques at different temperatures on the contents of total lipid and fatty acid profile of Artemia biomass. The results showed that among three indoor drying techniques, the shortest drying times (57-74 min) were observed in MWHA followed by HA (380-480 min) and oven drying (480-1320 min), respectively, while sun drying showed the longest dehydration duration (1380 min) compared to other drying methods. In addition, drying time decreased with increasing temperature. For the three indoor drying methods, the contents of total lipid and fatty acids of dried Artemia were not significantly different from the control in most cases. On the contrary, sun drying resulted in a high loss of these substances compared to the original material. Moreover, at the same drying temperature, the longer drying time caused a higher loss of nutrients in the dried products as shown by the values in the MWHA sample which was slightly higher than in other two drying methods. Nonetheless, between the three indoor drying methods significant differences were not observed (P>0.05). In general, the intermittent MWHA drying is a promising technique, which could produce high quality dried products in short drying times. However, it might not be suitable for large-scale application because of high capital investment and operating costs. Therefore, sun drying method should be improved to optimize the use of renewable energy sources through application of solar dryer.  

Predictive controlled-atmosphere-model for the opening of caps and sensory quality of fresh mushrooms (Agaricus bisporus)

Phan Thi Thanh Que, Bert Verlinden, Bart Nicolaï
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Fresh mushrooms (Agaricus bisporus) have a short shelf-life. The effects of O2 andCO2 concentrations and of storage temperature on the opening of caps and the sensory quality were studies. Eight different gaseous atmospheres were set up with combinations of O2 concentrations (3, 12, 16.5 and 21%) and CO2 concentrations (0, 3, 6 and 12%). The storage temperatures for each gas condition were 1, 6 and 12°C. The opening of caps and the sensory quality were modelled on the basis of a generalized logits model. As results, the O2 and CO2 in investigated concentration ranges did not give any effect on the quality of mushrooms stored at temperatures below 6°C up to 9 days. Temperature was the variable with the greatest influence on the opening of the caps, decreasing the sensory quality. At temperature of 12°C, a gas combination of 12% O2 and 6% CO2provided the best conditions but the shelf-life was less than 7 days. 

Effect of enzymatic treatments on lycopene in vitro bioaccessibility in high pressure homogenized tomato puree and chromoplast fraction

Nguyen Thi My Tuyen, Nguyen Minh Thuy
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Lycopene is a micro-nutrient to which health benefits have been ascribed. After high pressure homogenization, a decrease in lycopene in vitro bioaccessibility in tomato puree was reported. It was suggested that a new fiber network was formed entrapping lycopene.  In addition, the chromoplast sub-structure also constitutes an important physical structural barriers influencing lycopene release from the matrix and subsequent incorporation into micelles. In order to increase the lycopene in vitro bioaccessibility in tomato puree, enzymatic treatments using different cell wall degrading enzymes (Pectinex Ultra SP-L and Viscozyme) were applied to the homogenized tomato puree. Enzymatic treatments using phospholipase D and protease were also applied to a fraction enriched with chromoplast in order to enhance lycopene in vitro bioaccessibility. An in vitro digestion assay was used to investigate the effect of enzymatic treatments on lycopene bioaccessibility. Results showed that the enzymes worked effectively on solubilizing the new fiber network that was formed upon homogenization. However, no significant increase in lycopene in vitro bioaccessibility was found after any of the enzymatic treatments. By applying phospholipase D and protease enzymes on the fraction enriched with chromoplast, no further increase in lycopene in vitro bioaccessibility was found. Therefore, it is suggested that the chromoplast sub-structure, meaning how lycopene crystals are embedded within the chromoplast organelle, constitutes the most important barrier for lycopene bioaccessibility in tomato fruit. 

Extraction of bioactive compounds and spore powder collection from Ganoderma lucidum

Nguyen Minh Thuy, Nguyen Thi My Tuyen
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Ganoderma lucidum (G. lucidum), commonly known as lingzhi mushroom, contains active compounds known as beta glucans which are polysaccharides with immune-boosting effects. The complex sugars found in Ganoderma lucidum may stop growth and prevent the spread of cancer cells. It is also rich in phenolic compounds, which prevent the oxidative damage induced by free radicals generated in body cells. The content of this paper including (i) optimization extracting process based on the experimental design of time (15-45 minutes) and temperature (70-130oC) and (ii) fermentation of G. lucidum spore with Lactobacillus plantarum for breaking spore wall from 24 to 72 hours. Spores with broken walls can release the effective ingredients. Response surface methodology was successfully applied to describe the relationship between polysaccharide, phenol compounds content and extraction temperature and time. The quadratic models for both polysaccharide and phenol compounds extraction were significant (R2>0.95). From the results of numerical and graphical optimization methodology, the optimum extraction conditions were achieved at temperature of 130°C for 40-45 minutes. The optimum conditions (130°C, 40 min) were validated with actual polysaccharide and phenol compounds content of 667.5 mg/L and 631.25 mg GAE/L, respectively. The rate of spore wall breaking can become 52.38% after 48 hours of fermentation with Lactobacillus plantarum. The high antioxidant activity fungal spore powder was obtained. 

Novel naphthalene glycoside derivative from leaves of Cassia grandis L.f

Nguyen Ngoc Hanh, Phan Nhat Minh, LE TIEN DUNG, Nguyen Tan Phat, Mai Dinh Tri, Vu Duy Khanh, Nguyen Kim Phi Phung, Ngo Quoc Luan
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A new natural compound named casgranone C from methanol extracts of leaves of Cassia grandis L.f was isolated. Its structure was elucidated by MS, NMR spectra and by comparison with published data.

Estimation of family labor supply: Evidence from the MeKong River Delta in Viet Nam. Can Tho University Journal of Science

Huynh Truong Huy
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This article explores the data of 1,860 families living in the Mekong River Delta (MRD) region from the Viet Nam Household Living Standards Survey 2008 (called VHLSS 2008) to learn about their familial labor allocation in responding to changes of market wage. Theoretically, wage – one of the key factors influencing changes of family labor supply– is used to estimate a level of the shadow wage which is an exogenous factor in the labor supply function. Based on the survey data of 1,860 MRD families, findings showed that family labor supply is significantly sensitive to changes of both shadow wage and non-labor income. Family labor supply is being of a forward bending curve, while family tended to reduce its labor supply as a response of an increase of the non-labor income. Additionally, plot size was closely related to labor supply within a family. Consequently, results also indicate that IV estimation methodology is substantial to estimate impacts of changes of the economic opportunity (mainly wage) on family labor supply.