Progress 10/01/07 to 09/30/10
Outputs
OUTPUTS: We accomplished following activities according to the research timeline: a) Determine water vapor permeability of fish gelatin films made with different concentrations of gelatin; b) First, determine the optimum perimeters including concentration and temperature of solution, and spreading or dipping time when applying the complex of fish gelatin and preservatives to shrimps at a laboratory scale; then collaborate with shrimp farmers or catchers to conduct on-site research to scale up the experiments; and c) Conduct shelf-life tests for both fresh and frozen shrimps to ensure food quality and safety of fresh shrimps. PARTICIPANTS: Yifen Wang: principal investigator Jesse Chapple: co_PI Shaoyang Liu: research fellow Mingkang Jiang: PhD student TARGET AUDIENCES: Fisheries industry, scientists and engineers. Two of the most important technical and economic problems facing the shrimp industry are relatively short shelf life of fresh products and drip loss for frozen shrimp. Catfish skin gelatin based antibacterial edible films/coatings provide an ideal technique to solve both problems. The shrimp industry will be the immediate beneficiary of the study and the information provided by this research will be expended to other seafood. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
a) to investigate the structure characteristics of the added triacetin in the film using transmission X-ray microscope, influences of the triacetin to the film properties, and possible relationships between the distribution characteristics and the film properties. Gelatin from catfish skin was obtained by thermal extraction. Triacetin was added to gelatin in proportions of 0, 50, 100, and 150% of gelatin content to improve the hydrophobic properties of the resulting films. Tween 80 was also added as an emulsifier. Distribution of the introduced triacetin in the film was examined using transmission X-ray microscope (TXM). Other film properties, such as thickness, mechanical properties, water vapor permeability, water solubility, light transparency, and thermal properties, were also evaluated. Possible relationships between the distribution characteristics and the film properties were studied. b) to investigate the bactericidal effects of four types of solution on the fresh shrimp and their influences on its shelf-life. Fresh wild-caught medium size (about 7.22 g) brown shrimp (Penaeus aztecus) was obtained from Bon Secour, AL. Shrimp was transported in ice pack and treated immediately after arrival at the lab. Four types of treatment were used. They were A (Electrolyzed Acid Water, 40 ppm available chlorine), B (1.0 percent Potassium Sorbate solution), C (Control, pure water), and D (2.0% Sodium tripolyphosphate or STP solution). Treatments were carried out at 4 degree Celsius at a volume to weight ratio of 1.5: 1. Shrimp were submerged under the treatment solutions for 10 mins with occasional stirring and then drained for 5 mins. Three pieces of individual shrimp were put into one sample bag as one sample batch. Three sample batches were used on each sampling day for each treatment. Treated samples were put at 4 degree Celsius conditions. c) to evaluate the effectiveness of catfish skin gelatin based antibacterial edible coatings on prolonging shelf life and quality changes of fresh shrimp under ice storage condition. Antimicrobial coating was prepared by incorporating potassium sorbate (PS), sodium tripolyphosphate (STP), or both ingredients (Combined) in coating solution made from catfish skin gelatin. Shrimp samples were untreated, rinsed with water, or coated with the antimicrobial films, and then they were stored in ice under aerobic conditions. Samples were taken periodically and evaluated for total aerobic plate count (AP), psychrotrophic bacteria count (PB), near infrared spectrum (NIR), springiness, pH value, and color measurement. The results showed that the antimicrobial coating could retard microbial growth and prolong shelf life for up to 10 days. Partial least square (PLS) analysis produced an acceptable model fitting between the near infrared spectrum and the changes of microbial count in shrimp samples. The springiness and pH value of shrimp muscle were not affected by the coating treatments. Color parameter a* value increased linearly for all the treatments during the whole ice storage period.
Publications
- Jiang, M., Liu, S., Du, X., and Wang, Y. 2010. Physical properties and internal microstructures of films made from catfish skin gelatin and triacetin mixture. Food Hydrocolloids 24 (1): 105-110
- Jiang, M., Liu, S., and Wang, Y., 2011. Prolonging shelf life of fresh white shrimp (Penaeus vannamei) with catfish skin gelatin antimicrobial coating. Journal of Food Science (accepted)
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: We accomplished following activities according to the research timeline during last year (1/1/2009 to 12/31/2009): Objective 2) First, determine the optimum perimeters including concentration and temperature of solution, and spreading or dipping time when applying the complex of fish gelatin and preservatives to shrimps at a laboratory scale; and Objective 3) Conduct shelf-life tests for both fresh and frozen shrimps to ensure food quality and safety of fresh shrimps. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
2) Preparation of coating solutions Catfish skin gelatin was prepared using the method described by Yang et al. The coating solution was prepared by dissolving catfish skin gelatin in deionized water at 50 degree C. The total gelatin concentration in the base coating solution was 5% (wt/wt, dry weight basis). Glycerol was added at the concentration of 20% (wt/wt) of the gelatin amount. Three types of coating solution were obtained: (a) PS solution containing base solution plus 2% potassium sorbate (wt/wt), (b) STP solution containing base solution plus 2% sodium tripolyphosphate (wt/wt), (c) Combined solution containing base solution plus 2% potassium sorbate and 2% sodium tripolyphosphate (wt/wt). 3) to investigate the bactericidal effects of four types of solution on the fresh shrimp and their influences on its shelf-life. Shrimp samples were randomly assigned into five treatment batches consisting of one control batch (no surface wash at all), one water rinsed batch (rinsed with deionized water) and three gelatin coating batches mentioned earlier: PS, STP, and combined solutions. For each treatment, shrimp were immersed in the water or coating solution at a ratio of 1:2 (wt/v) for 60 s with gentle swirling of a glass rod to ensure fully contact of shrimp with the solution. After removal from the solutions shrimp were allowed to drain and air dried on a flat plate at room temperature for 10 min. Shrimps were then put in low density polyethylene plastic bags and stored in ice. Samples were taken on daily basis for shelf-life evaluation and other physical and chemical determinations. Onset of shrimp spoilage is considered to be 7 log CFU/g total aerobic plate count. Samples for drip-loss study were taken on monthly basis for 12 months. All the analysis was done in triplicate. Microbial analysis, texture measurement, pH value, color measurement, drip loss, statistical analysis were conducted.
Publications
- Jiang, M., Liu, S., Du, X., and Wang, Y. 2010. Physical properties and internal microstructures of films made from catfish skin gelatin and triacetin mixture. Food Hydrocolloids 24 (1): 105-110.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: We accomplished following activities according to the research timeline during last year (1/1/2008 to 12/31/2008): a) Determine water vapor permeability of fish gelatin films made with different concentrations of gelatin and b) Conduct shelf-life tests for fresh shrimps to ensure food quality and safety of fresh shrimps. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
a) to investigate the structure characteristics of the added triacetin in the film using transmission X-ray microscope, influences of the triacetin to the film properties, and possible relationships between the distribution characteristics and the film properties. Gelatin from catfish skin was obtained by thermal extraction. Triacetin was added to gelatin in proportions of 0, 50, 100, and 150% of gelatin content to improve the hydrophobic properties of the resulting films. Tween 80 was also added as an emulsifier. Distribution of the introduced triacetin in the film was examined using transmission X-ray microscope (TXM). Other film properties, such as thickness, mechanical properties, water vapor permeability, water solubility, light transparency, and thermal properties, were also evaluated. Possible relationships between the distribution characteristics and the film properties were studied. Triacetin distribution changed from homogeneous to heterogeneous with increased content in the film. Addition of triacetin caused decreased tensile strength (TS) and increased percent elongation (E%), water solubility, UV and visible light barrier properties, and glass transition temperature (Tg) of the film. Water vapor permeability of the film increased in some treatments (100 and 150% triacetin) possibly due to the heterogeneous distribution of the triacetin and increased emulsifier amount in the film. b) to investigate the bactericidal effects of four types of solution on the fresh shrimp and their influences on its shelf-life. Fresh wild-caught medium size (about 7.22 g) brown shrimp (Penaeus aztecus) was obtained from Bon Secour, AL. Shrimp was transported in ice pack and treated immediately after arrival at the lab. Four types of treatment were used. They were A (Electrolyzed Acid Water, 40 ppm available chlorine), B (1.0 percent Potassium Sorbate solution), C (Control, pure water), and D (2.0% Sodium tripolyphosphate or STP solution). Treatments were carried out at 4 degree Celsius at a volume to weight ratio of 1.5: 1. Shrimp were submerged under the treatment solutions for 10 mins with occasional stirring and then drained for 5 mins. Three pieces of individual shrimp were put into one sample bag as one sample batch. Three sample batches were used on each sampling day for each treatment. Treated samples were put at 4 degree Celsius conditions. Both the total viable count (TVC) and psychrotrophic microbial count (PMC) of the untreated and immediately after-treated shrimp were examinated. Additional samplings were made at 3, 5, 7 days after the treatment. In addition, texture measurement was conducted. Data were analyzed with GLM (General Linear Models) procedure in SAS (Statistical Analysis Systems Institute, Cary, N.C. USA). A p-value less than 0.05 indicates a significant difference in an analyzed dataset.
Publications
- Jiang, M., Liu, S., Xin, D. and Wang, Y. (2008). Studies on the physical properties of channel catfish (Ictalurus punctatus) skin gelatin film using transmission X-ray microscope. Journal of Food Hydrocolloids (submitted).
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