Published: 2021-08-14

Hygienic conditions of the processing environment and microbial loads of Tra fish (Pangasius hypophthalmus): Trimming step

Ngoc T. A. Tong, Tu C. Nguyen, Hang T. M. Nhan, & Tam N. T. Huynh
Electronic version: 29 Apr 2021 | DOI: 10.52997/jad.6.02.2021
Abstract | PDF (376.3K)

Abstract

During the processing of frozen Pangasius hypophthalmus fillets, the microbiological counts depend on the source of raw materials and processing conditions, those impact significantly on the  quality  of  the final product. In particular, trimming is considered a high-risk step of cross-contamination during processing. This study aimed to compare and evaluate the microbial quality at trimming step in four frozen Pangasius processing factories located in the Mekong Delta region. Trimmed Pangasius fillet and contact surfaces samples (i.e., gloves and processing tools) were examined including total mesophilic counts, Coliforms, E. coli and coagulase-positive Staphylococci (Staphylococci coa+). The results showed that total mesophilic counts on trimming Pangasius processed in A, B, C and D plant were 7.1 ➧ 0.4; 7.5 ➧ 0.7; 6.7 ➧ 1.1 and 6.0 ➧ 0.4 log CFU/g, respectively. Coliforms, E. coli and Staphylococci coa+ on trimmed Pangasius ranged 4.0 - 5.1; 2.1 - 3.7 and 1.8 - 4.2 log CFU/g, respectively. Thus, proper preservation of fillets during processing is suggested. Good manufacturing practices should implement effectively to minimize the risk of cross-contamination for the trimmed fillets.

Current status of acute hepatopancreatic necrosis disease (AHPND) and result of isolating AHPND-causing strains of farmed shrimp in Mekong Delta Region of Vietnam

Hieu V. Tran, Dung H. T. Mai, Binh T. Huynh, Hoa T. M. Nguyen, Hoan P. K. Nguyen, Toan T. Nguyen, Lien T. T. H. Tran, Ly H. Tien, Xuyen D. Nguyen, & Thuoc L. Tran
Electronic version: 29 Apr 2021 | DOI: 10.52997/jad.5.02.2021
Abstract | PDF (3.4M)

Abstract

Early mortality syndrome/acute hepatopancreatic  necrosis (EMS/AHPND) was first detected in China in 2009. The  disease spread rapidly to neighboring countries and emerged in almost major shrimp-producing regions in the world, including Vietnam. The disease has caused serious damage to the global shrimp industry and so far, there is no effective cure. In order to understand the current status of AHPND, and then to introduce effective prevention and detection measures, we collected data and shrimp samples in some provinces in the Mekong Delta to analyze and isolate the pathogenic strains. The results of our study conducted from 2014 - 2018 in four provinces (Ben Tre, Long An, Bac Lieu, Kien Giang) showed that AHPND damaged from 2.0 to 57.2% of the total shrimp farming area. In addition, we isolated 10 AHPND-positive strains via culturing and PCR. The results of representative sequencing of three strains LA1, LA5, and LA8 showed that they were 100% similarity with the previously published strain XN89. These isolated strains are used as a collection for further studies on the origin and mechanism of the disease by whole genome sequencing.

Evaluation of bacteriocin-producing lactic acid bacteria strains isolated from “nem chua Thu Duc”

Phuong T. Nguyen, Chi N. Vo, Tuyet T. A. Nguyen, Khoa D. A. Dinh, Tuyen P. B. Phan, Hang D. Hoang, & Thuy T. Le
Electronic version: 29 Apr 2021 | DOI: 10.52997/jad.8.02.2021
Abstract | PDF (651.5K)

Abstract

This study aimed to select some lactic acid bacteria (LAB) strains to produce bacteriocin isolated from two  different local brand names of nem chua Thu Duc, a Vietnamese traditional fermented meat product. Eight different LAB strains were isolated from products. However, only Pedio- coccus pentosaceus isolated from 72-h fermented “Ba Chin” products and Weissella paramesenteroides isolated from 120- h fermented “Diem” products were selectively screened for their bacteriocin production. The antimicrobial activity was detected by  the  agar  diffusion  method  against  Escherichia coli ATCC 25922, Salmonella enterica serovar Typhimurium ATCC 13076, Staphylococcus aureus ATCC 6538, and Bacil- lus cereus ATCC  25924  used  as  target  strains.  Bacteriocin of Pediococcus pentosaceus strain showed a high antibacterial ability with  a sterile  ring diameter  that  produces an  aver- age of 12.20 - 16.07 mm. Bacteriocin of Weissella paramesen- teroides strain only showed inhibitory activity on the growth of indicator microorganisms with an average inhibitory ring diameter of 9.75 - 15.27 mm. In  conclusion,  it  seems  like both bacteriocin-producing P. pentosaceus and W. parame- senteroides give potential applications as a starter culture, bio-preservation and bio-safety control in fermented meat as well as other kinds of fermented foods.

Optimization of extraction conditions of flavonoids from Houttuynia cordata Thumb leaves

Anh T. Vu, Phung M. Phan, Phuc T. D. Nguyen, Phuc N. H. Nguyen, & Vi T. T. Vo
Electronic version: 30 Apr 2021 | DOI: 10.52997/jad.7.02.2021
Abstract | PDF (679.3K)

Abstract

This study was conducted to investigate the application of cellulase enzyme in the extraction of flavonoids from Houttuynia cordata Thumb leaves and optimize the extraction conditions. Independent variables, including enzyme concentration (25 - 100 ➭g/mL), temper- ature (30 - 50oC), time (30 - 120 min) and ratio of raw materials to enzyme (1:15 - 1:30 g/mL), were investigated. Extraction conditions of flavonoids were designed according to Central Composite Design - Uniform Precision (CCD), a response surface methodology using a software JMP Pro version 13. The results indicated that the optimal extraction conditions were found to be enzyme concentration (78.0 ➭g/mL), temperature (41 C), time (90 min), and the ratio of material to the enzyme (1:26 g/mL). Under such conditions, the highest content of flavonoids (24.04 ➧ 0.05 mg/g, dry matter) was obtained and validated. It can be concluded that the flavonoids can be optimally extracted under the optimal extraction conditions with assistance of cellulase.

Effects of two hydroponic components on water quality, snakehead fish growth and leaf mustard production in aquaponic system

Tu P. C. Nguyen, Ha N. Nguyen, Thuy T. T. Thai, Phong T. Tran, & Tri N. Nguyen
Electronic version: 29 Apr 2021 | DOI: 10.52997/jad.4.02.2021
Abstract | PDF (427.1K)

Abstract

Aquaponic model is a farming system that integrates a recirculating aqua- culture system with hydroponics. There are three hydroponic methods commonly employed in the aquaponics systems: the media bed (MB), the nutrient film technique (NFT) and the deep-water culture - floating rafts (DWC). This study was conducted to evaluate effects of two hydroponic systems (DWC and MB) on water quality parameters, growth rate of fish and development of vegetable in the aquaponic model of snakehead fish (Channa striata) and leaf mustard (Brassica juncea). Snakehead fish were stocked with a density of 40 fish/75 liters of water and were cultured for 167 days. The results showed that daily temperature, pH and dissolved oxygen parameters in the two systems were almost the same and relatively stable while the electrical conductivity in the MB was much higher than that in the DWC. Similarly, the levels of the  parameters  weekly  moni- tored (ammonia, nitrite, nitrate,  total  phosphorus,  and  alkalinity)  in  the MB were higher than those in the  DWC.  At  the  end  of  the  experiment, final weight, weight gain, specific growth rate and survival rate of fish in the MB treatment were higher than those in the DWC treatment, but the feed conversion rate of fish in the MB was lower than that in the DWC. On the contrary, vegetable yields in the  DWC  were  significantly  higher than those in the MB. In general, the DWC aquaponics work better than the  MB  system.

Evaluation of the specific combining ability (SCA) for yield and brix of seven Cucumis melo. L inbred lines of the sixth generation

Tuan Q. Huynh, Dan T. Vo, Hiet D. Hoang, Lam V. Tran, Trinh T. T. To, & Man T. T. Le
Electronic version: 29 Apr 2021 | DOI: 10.52997/jad.1.02.2021
Abstract | PDF (379.4K)

Abstract

The objective of the experiment was to screen Cucumis melo L. inbred lines for high potential general combining ability and potential hybrids combinations for F1 hybridization. The experiment was conducted as a randomized complete block design (RCBD) with 29 treatments [21 hybrid combinations, control (TL3 hybrid) and seven Cucumis melo L. inbred lines I6], each with three replicates. Estimating the specific combining ability (SCA) of Cucumis melo L. inbred lines for breeding of F1 hybrid cultivars was carried out at the Research and Development Center for Hi-tech Agriculture in Ho Chi Minh City. Based on the specific combining ability of yield trait and total soluble solids (Brix) content of 21 hybrid lines from seven inbred linesfollowing diallel method (Griffing 4 model), four potential hybrid lines (H41.6 x H58.6, H53.6 x H77.6, H32.6 x H41.6 v  H53.6 x H58.6) yielded 10% higher than the control variety and gave fruits of oval shape, even fruit-net and low diseases infection.

Estimation of the specific combining ability (SCA) of eight bitter gourd (Momordica charantia L.) inbred lines in the sixth generation

Trinh T. T. To, Hiet D. Hoang, Man T. T. Le, Lam V. Tran, Phuong T. B. Nguyen, Tuan Q. Huynh, Bich T. Thai, & Dan T. Vo
Electronic version: 30 Apr 2021 | DOI: 10.52997/jad.3.02.2021
Abstract | PDF (401.9K)

Abstract

Estimating the Specific Combining Ability (SCA) of bitter gourd (Momordica charantia L.) inbred lines for breeding F1 hybrid cultivars was performed at the Research and Development Center for Hi-tech Agriculture in Ho Chi Minh City from September to December 2019. The objective of the study was to select the outstanding hybrid combinations from diallen method to produce F1 hybrid cultivars. The results from estimating the SCAs based on the productivity characteristic of 28 hybrid combinations produced from eight bitter gourd I6 inbred lines (Q16, Q65, Q80, Q86, Q75, Q06, Q81 v  Q87) following diallen method showed that four promised hybrid combina-tions (Q65/Q80, Q86/Q75, Q06/Q81 and Q81/Q87) performed over10% higher SCA values and heterosis than the control, and they were less susceptible to infectious diseases. Fruit characteristics and yield of four hybrid combinations included fruit length of 16.0 to 17.6 cm; fruit width of 6.2 to 6.8 cm; 132.2 to 151.7 g/fruit and average yield of 4.1 to 4.3 tons/1000 m2.

The distribution and presence of versicular-arbuscular mycorrhiza fungi in rhizosphere soil of Da Xanh pummelo in Ba Ria Vung Tau province

Huong N. D. Thai, Duong T. T. Pham, & Linh Nguyen
Electronic version: 29 Apr 2021 | DOI: 10.52997/jad.2.02.2021
Abstract | PDF (280.9K)

Abstract

The study was carried out to determine the distribution and pres-ence of versicular-arbuscular mycorrhiza (VAM) fungi in rhizo-sphere soil and roots of Da Xanh pummelo in Phu My town, Ba Ria Vung Tau province. The rhizosphere soil and root sampleswere collected from 6 - 7 years old pummelo of two main soil types, on two soil layers at depths of 0 - 20 cm and 20 - 40 cm, at2/3 and the edge of canopy. The results showed that the presence of VAM spore density was higher in red basaltic soil (ferralsols) than black soil (luvisols), and common exist on the topsoil layer (0 - 20 cm) as well as the edge of canopy. Glomus and Acaulospora were two most abundant genera in survey areas, and the propor-tion of mycorrhizal spores ranged from 53.18 ± 2.59% to 58.54 ± 0.46 and from 23.68 ± 2.96% to 29.33 ± 0.64%, respectively. Increasing the soil depth negatively affected on spore density of VAM fungi. The VAM fungi composition aslo changed with soil depth. The percentage of root colonization by VAM fungi ranged from 56.20 ± 3.11% to 62.00 ± 3.37%, and the highest percentage of root colonization by VAM fungi was detected in red basaltic soil.