HUE UNIVERSITY UNIVERSITY OF SCIENCE LE NHAT TAM

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1 HUE UNIVERSITY UNIVERSITY OF SCIENCE LE NHAT TAM INVESTIGATE THE VARIATION OF THE FACTORS INFLUENCING THE POST-HARVEST QUALITY OF BLACK TIGER SHRIMP DURING STORAGE AT 0 O C Summary of PhD Dissertation HUE,

2 HUE UNIVERSITY UNIVERSITY OF SCIENCE LE NHAT TAM INVESTIGATE THE VARIATION OF THE FACTORS INFLUENCING THE POST-HARVEST QUALITY OF BLACK TIGER SHRIMP DURING STORAGE AT 0 O C Major : Organic chemistry Code: PhD DISSERTATION Supervisors: 1. Associate professor. Tran Thi Van Thi 2. Associate professor. Do Thi Bich Thuy Hue,

3 INTRODUCTION Aquatic products are important sources of nutrients containing high levels of amino acids, peptides, proteins and other essential nutrients for daily meals. The decomposition of aquatic species occurs during preservation by microbial activity and chemical reactions. The method used to evaluate the quality of aquatic products depends on their characteristics, and the preservation conditions. Each method only assessed one stage of change, or one aspect of the preservation process. Thus, a combination of different methods is very neccessary to evaluate all changes of aquatic products during storage giving more accurate, and reliable results. Therefore, we carried out the research entitled " Investigate the variation of the factors influencing the post-harvest quality of black tiger shrimp during storage at 0 o C " In this work, we conducted a study to find out the correlation among sensory, chemical and microbial changes during preservation of shrimp (Penaeus monodon). Basing on the obtained results, the method using to classify the quality of tiger shrimp is suggested 2. Research objectives 3. Material Black tiger shrimp (Penaeus monodon), phylum: Arthropoda, subphylum: Crustacea, order: Decapoda, family: Penaeidae, genus: Penaeus, species: Penaeus monodon. 4. Methodology - Methods for assessing the quality of black tiger shrimp: determining 1

4 total aerobic microorganism (TVC), and QIM - Quantitative methods of chemical indices: TVB-N, TMA-N, histamine, hypoxanthine and ph values. - Statistical analysis: using Statgraphics centurion XVI software, linear model by MS. Excel (2010). 5. New scientific results The results indicated some important findings as follows: + It is a very first time that histamine and hypoxanthine indices were used to evaluate the shrimp quality. + Changes in the sensory and chemical qualities of black tiger shrimp were observed during storage at 0 o C. + The linear regression models between QI score, TVB-N, TMA-N, histamine or hypoanthine with storage time were found. + The combination of sensory evaluation and chemical methods could be appled to classify shrimp quality. 6. Conclusion The results of this work provided primary infomation in evaluating the quality of aquatic products after harvest. CHAPTER 1. LITERATURE REVIEW 1.1 Introduction Characteristics of black tiger shrimp Chemical composition of some shrimp species 1.2 Type of spoilage and sensory changes during storage: spoilage is caused by microorganisms, enzymes or chemical reactions. 1.3 Quality assessing method: sensory evaluation, chemistry, physics, and microbiology measurement. 1.4 Developing QIM for black tiger shrimp: Developing a profile describing quality attributes of black tiger shrimp during storage; establishing QIM assessment, examining quality of shrimp according to QIM; evaluating QIM program. 2

5 1.5 Quantitative method: high performance liquid chromatography (HPLC); ultraviolet-spectral method 1.6 Some models of quality assessment are based on a combination of different methods Chapter 2. RESEARCH OBJECTIVES AND METHODS 2.1. Research objectives - Investigating the correlation between sensory, chemical, and microbiological changes of tiger shrimp preservation (Penaeus monodon) during storage at 0 C basing on quality indices. - Developing the quality classification scale of tiger shrimp basing on quality indices Research content The research content of the study consisted 5 parts: - Developing method for assessing the quality of shrimp (Penaeus monodon) by QIM. - Developing quantitative method of hypoxanthine on shrimp by HPLC. - Developing linear regression equations between TVB-N, TMA-N, histamine and hypoxanthine. - Investigating the sensory and chemical changes of black tiger shrimp during storage at 0oC and the correlation between sensory quality and chemical quality. - Developing the quality classification scale basing on sensory and chemical indices MATERIALS, CHEMICALS AND EQUIPMENTS Materials Black tiger shrimps (Penaeus monodon) were provided by 3 different farms located in Ca Mau Province, Vietnam. Each kilogram of shrimp has from 26 to 30 pieces. Shrimps haing defects or shell broken were removed. Thirty kilograma of fresh tiger shrimp were harvested, washed with water and then put in 300 polyethylene bags ( cm, Alcoa Inc., Richmond, VA 23261, USA). These bags are placed in styrene boxs with ice and the ratio between ice and shrimp was 1: 2 (w / w). After that, shrimps were tranported to the laboratory within 8 hours. Polyethylene bags of shrimps were kept at cold temperature 0 C in the laboratory. Figure 2.1 describes the process. 3

6 Farm 1 Farm 2 Farm 3 Shrimp harvested from farm (10 kg per farm) Washed using filtered clean flowing water Packaged in polyethylene bags Stored in ice in polyethylene boxes Transported to the laboratory Shrimp was stored at 0 0 C Analysis TVC n =3 QIM n =3 TVB-N n = 3 TMA-N n = 3 His n = 3 Hx n = 3 Fig 2.1 Experimental design Chemicals and equipments Fig. A schematic overview of the experimental study. QIM refers to quality index method; TVB- N refers to total volatile basic nitrogen; TMA-N refers to trimethylamine nitrogen; His refers to histamine; Hx refers to hypoxanthine, TVC refer to total visible counts The chemicals used in this research were good quality MEASUREMENT Determining TVC method (Leboffe et al.) [140] QIM method Sample preparation (according to 2.3.1) Selecting and training the panel The panel was selected and trained carefully for the sensory evaluation [226]. Steps for organizing the panel: Step 1: Primary recruitment for the panel 4

7 Step 2: Recruiting according to the requirement Step 3: Training the testers Step 4: Final recruitment the testers for official assessment - Primary recruitment for the panel [110] 20 people participated in the recruitment, and selecting 12 members for the panel. -Training the testers (TCVN 11045: 2015) [239]. During this process, 12 members attended the training sessions and recruitment. During this period, six members were considered for the official panel Selectng testers in the official sensory evaluation -Selecting testers for the official panel (TCVN 11045: 2015) Six testers having the ability, health and time for the sensory evaluation process were selected.: Guidance on sensory evaluation in laboratory for fish and shellfish [5] Assessing quality Assessing quality of shrimp according to QIM includes the following steps: + Describing the attributes of black tiger shrimp + Developing QIM + Applying QIM to determine the QI for each piece of shrimp every day during storage + Assessment QIM method 2.5. CHEMICAL INDICES MEASUREMENT Sample preparation 5

8 Sample preparation was conducted according to section TVB-N The concentration of TVB-N was determined according to TCVN 9215: 2012 [7] TMA-N The TMA concentration was measured according to AOAC [8] Histamine Histamine was determined by the HPLC accoding to the earlier report of Gouygou et al. (1987) Hypoxanthine Hypoxanthine in shrimp was extracted as described by Ryder (1985) [217] and was measured according to Kock et al. [127] and Nacalai's method [267] ph The ph value was performed according to the report of Özogul et al. [193] EXPERIMENTAL DESIGN Determining aerobic microorganisms Experiment 1: Investigating the amount of TVC in black tiger shrimp during storage Developing QIM and evaluating quality of shrimp according QIM Experiment 2: Developing desriptors Experiment3: Verificating desriptors by Cata method Experiment 4: Evaluating shrimp quality every day during storage days, establishing the correlation between QI and storage time. Experiment 5: Evaluating the accuracy of QIM 6

9 Investigating the change of chemical indices during storage Sample preparation Measuring the changes in quality indices Experiment 6: Selecting the method to determine the hypoxanthine content of black tiger shrimp Experiment 7: Developing the standard curve, recovery efficiency, LOD, LOQ and RSD values Experiment 8: Evaluating the TVB-N content in black tiger shrimp samples during storage Experiment 9: Evaluating the TMA-N content in black tiger shrimp samples during storage Experiment 10: Evaluating the histamine content in black tiger shrimp during storage Experiment 11: Evaluating the hypoxanthine content in black tiger shrimp during storage. Experiment 12: Determining the ph value of black tiger shrimp during storage Statistical analysis All experiments were carried out 3 times. All data were processed by Statgraphics centurion XVI software (P<0.05), MS. Excel (2010). CHAPTER 3. RESULTS AND DISCUSSION 3.1 Results of TVC in shrimp during storage. Fig 3.1 showed the number of TVC in shrimp from the day 1 to 10. There was no difference in TVC during the first 7 days of storage, the average value of log cfu/g was The number of TVC at day 8, 9 and 7

10 10 was 5,84; 6,39; 6,37, respectively. As a result, the number of TVC increased rapidly from the 8 th of storage. TVC 8(logcfu/g) Days Fig 3.1 The changes of TVC in shrimp during 10 days of storage at 0 C According to International Commission on Microbiological Specifications for Foods (ICMSF), the maximum log cfu / g of frozen shrimp was 6. This is also in agreement with the regulation of Health Ministry (No. 46/2007 / QD-BYT, 19 December 2007). Thus, tiger shrimp stored at 0 C had a shelf life up to 8 days basing on microorganism aspect Developing QIM and evaluating shrimp quality according to QIM QIM model for quality evaluating of black tiger shrimp. The QIM (Table 3.1) was developed during training panel basing on TCVN [2] and previous reports [4], [22], [91], [291]. Table 3.1 QIM for black tiger shrimp Attribute Scor Descriptors s e Light pink, no black spot 0 Light blue, no black spot 1 Color Head Light blue turns to light black 2 Big black mark 3 8

11 Structure Odor Body Tail Flesh Structu re Flesh Odor Blue, no black spots, shiny 0 Grey blue, slightly yellow, no black spot 1 Reddish brown, black spots 2 Black body 3 Light pink, no black spot 0 Light blue 1 black spots not more than two tail at the bottom 2 Visible turbidity at the tail 3 Fresh, trasparent, with no black spot 0 Turning to turbidity 1 Pale, the position near the head was light blue 2 The position near the head was light yellow or green 3 Intact 0 Head was slightly loose to the body 1 Head was separated with the body 2 Head was separated with the body, soft shell 3 Firm, elastic 0 Less elastic 1 Soft 2 Very soft 3 Fresh shrimp characteristic odor 0 Less fresh 1 9

12 No odor, slight ammoniac odor 2 Unpleasant odor, strong ammoniac odor Quality changes of black tiger shrimp during storage Fig. 3.2 presented the quality changes of shrimp during storage according to QIM Fig. 3.2 Linear Regression model between storage time and QI of shrimp The results indicated that QI had linear correlation with storage days. This finding was in accordance with earlier reports (Martinsdöttir et al., 2001) and [107], [171]. According to this obtained equation, we can estimate the shelf life of shrimp Evaluating the accuracy of QIM The QIM evaluation process was presented in the experiment 5. Ten shrimp samples were used to test the QIM method. The results of estimated storage time and real storage time were shown in Fig

13 Fig. 3.3 Testing the accuracy of QIM method according to estimated storage time and real storage time Quality classification of shrimp by QI According to Hanpong et al. [91], the evaluation scale for color, taste and structure of black tiger shrimp stored at 0 C was from 1 to 9, where 1= extremly like and 9= extremly dislike. The results showed that shrimp preserved from 1 to 2 days was perfect quality, from 3 to 5 days was good quality, from day 6 to day 7 was moderate quality, at day 8 was still acceptable quality. After the 8 th day, the quality of shrimp was unacceptable. Jayaweera and Subasinghe et al. [113] found that type 1 shrimp (Penaeus indicus) chilled storage had a shelf life from 1 to 3 days, type 1 shrimp had shelf life until 7 days, accepted quality till 10 days. After 10 days, shrimp was rejected due to poor quality. Cann [38] also reported that black tiger shrimp preserved at 0 C decreased the quality of taste from 2 to 4 days and appeared black spots from 6 to 9 days. Relly et al. [209] indicated that the quality of shrimp reduced after 2 days of storage at 0 C. The results of this work showed that storing black tiger shrimp at 0 C maintained its fresh attributes until day 4 and the quality changed significantly from day 5. At the 5 th day, the decomposition of collagen, 11

14 protein, amine, lipid and fatty acid occurred. Therefore, the changes in color, odor and structure were detected clearly. The spoilage symptom appeared at the 8 th day. According to the obtained results, the shelf-life of black tiger shrimp stored at 0 C was 8 days and the quality classification of shrimp was shown in Table 3.2. Table 3.2 Quality classification of shrimp by QI Classification QI Perfect 3,27 Good 3,67 7,47 Moderate 7,47 11,37 Acceptable 11,37 14, DEVELOPING METHOD FOR HYPOXANTHINE DETERMINATION IN SHRIMP Result selection method Determining hypoxanthine concentration was conducted as previous report of Kok et al. (1993) Standard curve Standard curve was established at 6 concentrations of hypoxanthine: 0.01ppm; 0,05ppm; 0.1ppm; 0.5 ppm; 1ppm and 3ppm. Each concentration was performed 3 times (Fig. 3.4). 12

15 S y = x R² = ppm Fig 3.4 Linear regression model between peak area and concentration The results of HPLC showed the correlation between the peak area and the concentration. The equation of standard curve was y= 126,35x + 10,285 (R2 = 0,9977) Determine LOD and LOQ values 0.01 ppm hypoxanthine standard was used (7 times) to evaluate LOD. The value of LOD = 3Cm / T [206], the empirical data was LOD = / = ppm, LOQ = 3LOD = ppm Determining the relative standard deviation (RSD) RSD values are determined on 10 standard samples with 1ppp concentration. The RSD value was 5.32% Recovery efficiency (H) Experiment 7 was carried out to determine the recovery efficiency H, and the average H = 90.10% QUALITY CHANGES OF SHRIMP BASING ON QUALITY INDICES TVB-N TVB-N concentration was measured in experiment 7. The changes of TVB-N in shrimp during storage were shown in Fig The TVB-N value consisted of TMA-N, DMA-N, NH 3 and volatile amines. 13

16 12 TVB-N 50 TVB-N y = x R² = Ngày y = x R² = Ngày Fig. 3.5 TVB-N concentration during storage In general, the amount of TVB-N in shrimp was significant difference among storage days. TVB-N values increased slowly from day 1 to 4 (6.47 to mg/100g, respectively) and leveled up rapidly from day 5. Figure 3.5 showed that the angular coefficients of two linear regression equations representing the correlation between TVB-N content and 2 stages of storage (day 1-4 and day 5-10) were different TMA-N TMA-N concentration was measured in experiment 8. The changes of TMA-N in shrimp during storage were shown in Fig

17 TMA-N y = x R² = Days TMA-N y = x R² = Days Fig. 3.6 TMA-N concentration during storage The TMA-N concentration in shrimp was significant difference among storage days (p < 0,05). The change of TMA-N had the similar trend to TVB-N. TMA-N increased slowly from day 1 to 4 (0,66 to 1,51 mg/100 g, respectively) and leveled up rapidly from day 5. The TMA-N content reached the maximum value at day 10 with 10,45 mg/100 g Histamin Histamin concentration was measured in experiment 9. The changes of histamin in shrimp during storage were shown in Fig In general, histamine content in shrimp was significant difference among storage days (p < 0,05) Histamine y = 0,16x + 0,31 R² = 0,994 Days Histamine y = 0,44x - 1,18 R² = 0,991 Days Fig 3.7 Histamin concentration during storage 15

18 The histamine content in shrimp related to the metabolism of microorganisms, the rate of formation varied from the first stage (day 1 to 4) to the second stage (day 5 to 10). In the first stage of storage, the histamine level increased slowly (from 0.46 mg / 100 g to 0.95 mg / 100 g). In the second stage, histamine content increased rapidly from 1.13 mg / 100 g to 3.23 mg / 100g Hypoxanthine Fig. 3.8 showed the hypoxanthine content in shrimp during storage. 4 Hx y = x R² = Ngày Fig. 3.8 Hypoxanthine concentration during storage Overall, hypoxanthine content in shrimp increased significantly during storage (p <0.05). The linear regression equation describing the correlation between hypoxanthine content and storage time was y = 0.25x (R 2 = 0.976) where y: the hypoxanthine content, x: the storage time. In comparison with the TVB-N, TMA-N, and histamine, hypoxanthine content increased linearly and there was no difference between the two periods of storage from day 1 to 4 and day 5 to ph The ph change was shown in Fig The ph value on the 1 st day was 7.07 and decreased to 6.93 on the 3 rd day. Then the ph started to rise on day 4 until day 10. The reduction in ph might be due to the decomposition of glycogen at the initial time. The increase of ph was because of the breakdown of the protein producing biological amines. 16

19 7.8 ph Ngày Fig ph value of shrimp during storage 3.5. Correlation equation between chemical quality indices and QI sensory Table 3.3 summarized the changes in quality of black tiger shrimp during storage. The three indices including TVB-N, TMA-N and histamine related to bacterial counts, therefore, the concentration of TVB-N, TMA-N and histamine was significant difference in the two periods of storage (day 1 to day 4 and day 5 to day 10). The results indicated that chemical quality indices linearly correlated with the storage time. Table 3.4 presented the linear regression equations of quality indices. 17

20 Storage time QI TVB-N (mg/100g) TMA-N (mg/100g) Histamine (mg/100g) Hypoxanthine (µm/g) ph Day 1 1,53 b ± 0,06 6,47 a ± 0,09 0,67 b ± 0,02 0,46 b ± 0,02 0,68 b ± 0,03 7,07 a ± 0,02 Day 2 3,67 c ± 0,055 7,77 b ± 0,08 0,89 c ± 0,02 0,66 c ± 0,03 0,78 c ± 0,04 6,75 b ± 0,03 Day 3 5,60 d ± 0,10 9,09 c ± 0,04 1,08 d ± 0,02 0,79 d ± 0,01 0,95 d ± 0,04 6,93 c ± 0,03 Day 4 7,47 d ± 0,06 11,39 d ± 0,07 1,51 e ± 0,02 0,95 e ± 0,02 1,02 d ± 0,01 7,09 a ± 0,01 Day 5 9,53 e ± 0,06 14,57 e ± 0,09 2,09 f ± 0,03 1,13 f ± 0,02 1,38 e ± 0,02 7,20 d ± 0,01 Day 6 11,37 f ± 0,12 18,89 f ± 0,10 3,34 g ± 0,03 1,35 g ± 0,01 1,59 f ± 0,03 7,29 e ± 0,03 Day 7 12,93 g ± 0,12 22,73 g ± 0,06 5,15 h ± 0,03 1,88 h ± 0,02 2,07 g ± 0,02 7,36 f ± 0,04 Day 8 14,33 h ± 0,12 28,15 h ± 0,06 7,36 i ± 0,04 2,41 i ± 0,01 2,13 g ± 0,02 7,43 g ± 0,04 Day 9 15,93 i ± 0,25 32,30 i ± 0,03 9,14 k ± 0,05 2,83 k ± 0,01 2,49 h ± ,59 h ± 0.04 Day 10 16,93 k ± 0,12 37,52 k ± 0,07 1,48 l ± 0,07 3,23 l ± 0,02 2,87 i ± ,71 i ± 0.02 TVB-N = 1,60x + TMA-N = 0,28x + 0,35 His = 0,16x + 0,31 Linear 4,68 R 2 = 0,958 R 2 = 0,994 QI = 1,72 x + 0,55 Hx = 0,25x + 0,23 Giá trị ph không regression R 2 = 0,978 (x: 1 4) (x: 1 4) R 2 = 0,993 R 2 = 0,976 tuyến tính với thời equation (x: (x: 1 4) TMA-N = 1,76x +6,93 His = 0,44x -1,18 (x: 1 10) (x: 1 10) gian bảo quản storage time) TVB-N = 4,52x R 2 = 0,994 R 2 = 0,991 +8,57 (x: 5 10) (x: 5 10) 18

21 R 2 = 0,991 (x: 5 10) Table 3.3. QI, TVB-N, TMA-N, histamine, hypoxanthine and ph during storage Table 3.4. Linear regression equation between chemical quality indices of shrimp Linear regression equation between chemical quality indices of shrimp (day 1 to 4) TMA-N Histamine Hypoxanthine TVB-N TVB-N = 5,69(TMA-N) + 2,76 R 2 = 0,996 TVB-N = 9,89His 1,61 R 2 = 0,966 TVB-N = 15,81Hx 2,32 R 2 = 0,930 TMA-N TMA-N = 1,72His 0,19 R 2 = 0,947 TMA-N = 0,33Hx + 0,35 R 2 = 0,894 Histamine His = 1,60Hx + 0,4 R 2 = 0,968 Linear regression equation between chemical quality indices of shrimp (day 5 to 10) TVB-N TVB-N = 2,55(TMA-N) + 9,40 R 2 = 0,980 TVB-N = 10,12His + 3,75 R 2 = 0,978 TVB-N= 18,96Hx + 6,88 R 2 = 0,978 19

22 TMA-N Histamine TMA-N = 3,97His 2,21 R 2 = 0,998 TMA-N = 7,30Hx 6,16 R 2 = 0,963 His = 1,85Hx 1,00 R 2 = 0,968 20

23 3.6. The proposal model to classify the quality of black tiger shrimp basing on the combination of QIM method and chemical quality indices This work suggested that the classification of shrimp quality was divided into four categories: Perfect, good, moderate and acceptable. Table 3.5 showed the sensory evaluation scores (QI) and the values of the chemical quality indices for each category. Table 3.5. Classification of shrimp (Penaeus monodon) basing on the combination of QIM method and chemical quality indices Classification Perfect Good Moderate Acceptable QI 3,67 3,67 7,47 7,47 11,50 11,50 14,50 TVB-N 7,77 7,77 11,37 11,37 18,89 18,89 28,15 TMA-N 0,89 0,89 1,51 1,51 3,34 3,34 7,36 His 0,66 0,66 0,95 0,95 1,35 1,35 2,41 Hx 0,78 0,78 1,02 1,02 1,59 1,59 2,13 CONCLUSION The results of this thesis Evaluating the effects of factors on quality of shrimp (Penaeus monodon) during storage at 0 C after harvest indicated some important findings as follows. 1. It was concluded, that QIM was able to evaluate the changes in sensory attributes in order to classify the black tiger shrimp quality. Shrimp quality was classified into 4 levels: perfect, good, moderate and acceptable and shelf life of shrimp stored at 0 C was up to 8 days. 2. At the 8 th of storage, the values of the quality indices were TVB-N = mg N / 100 g, TMA-N = 7.36 mg N / 100 g, His = 2.41 mg / 100

24 g, Hx = 2.13 μm / g, QI = Developing method to measure the hypoxanthine content in shrimp during storage by HPLC. 4. R 2 value in the linear regression equation containing chemical indices showed a strong correlation between TVB-N, TMA-N, histamine and hypoxanthine in tiger shrimp preserved at 0 C. This is the new scientific finding, the values of the indices can be found from the regression equation. 5. The spoilage process of black tiger shrimp was divided into two stages: autolysis (from day 1 to 4) and decomposition (from day 5 to day 10). The correlation between TVB-N, TMA- N and histamine was described by two linear regression equations at these two stages. This is also the new scientific finding. 6. It is the first time, two chemical indices of His and Hx were used to assess shrimp quality and proved to be strong correlation with shrimp quality. This point is new as well. 7. Developing the method to examine the quality of black tiger shrimp basing on the combination of sensory evaluation and chemical indices. This method proved to be efficient in assessing the shrimp quality. It is new scientific result. PUBLICATIONS International journal 1. Le, N. T., Doan, N. K., Ba, T. N., & Tran, T. V. T. (2017). Towards improved quality benchmarking and shelf-life evaluation of black tiger shrimp (Penaeus monodon). Food Chemistry, 235, Vietnamese journals

25 1. Le Nhat Tam, Tran Thi Van Thi (2015), Preliminary studies assessing the quality balack tiger shrimp by sensory evaluation and combined with the quantitative indicators trimethylamin, total volatile base, histamine, Journal chemistry, 53, Le Nhat Tam, Doan Nhu Khue, Tran Thi Van Thi (2016), Chemical quality indices for freshness evaluation of black tiger shrimp (Penaeus monodon), Journal science & technology, 54(2B), Le Nhat Tam, Nguyen Nam Giao, Tran Thi Ngoc Nhung, Dao Bich Duyen, Le Thi Hong Nhung, Nguyen Ba Thanh, Tran Thi Van Thi (2017), Development of quality index method to assess freshness and shelf-life of black tiger shrimp (Penaeus monodon) stored at 0 C, Journal science & technology, Hue University, 126(1B), Le Nhat Tam, Doan Nhu Khue, Tran Thi Van Thi (2017), Survey concentration of hypoxanthine and Histamine in black tiger shrimp stored at 0 C, Journal chemistry, 55(1), Le Nhat Tam, Huynh Nguyen Que Anh, Le Tan Khanh Trinh, Doan Nhu Khue, Tran Thi Van Thi, Đo Thi Bich Thuy (2017), The effect of organic acids salts on the quality and shelf- life of black tiger shrimp (Penaeus monodon) in the storage at 0 0 c, Journal chemistry, 55(4E23), Le Nhat Tam, Huynh Nguyen Que Anh, Le Tan Khanh Trinh, Tran Thi Van Thi, Do Thi Bich Thuy (2017), Changes in chemical, and microbiological quality indices of black tiger shrimp (penaeus monodon)

26 during stored in 0 o c, Journal science & technology, Hue University of science.