- Title
- High pressure processing of Barramundi fish (Lates calcarifer)
- Creator
- Truong, Binh
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2017
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- High pressure processing (HPP) is well-known as an innovative processing technology that can extend shelf-life and improve physicochemical properties of fish muscle during storage. However, research for all potential HPP applications on barramundi fish has not been done before. In this study, HPP was applied prior to conventional freezing to improve physicochemical properties of barramundi muscle and to abate the adverse effects of freezing on barramundi muscle during frozen storage. HPP was also used with or without the combination of chitosan coating to extend the shelf-life of barramundi during chilled storage. HPP was also employed to produce barramundi gels, especially, to reduce salt concentration in these gels. For raw barramundi muscle stored in frozen condition at - 18 °C, application of HPP at 150 MPa and initial temperature of 4 °C for 3 min prior to freezing resulted in barramundi fillet with higher hardness and springiness, lower drip loss and stable pH compared to non-pressurised samples during frozen storage for up to 18 weeks. HPP under these conditions also did not induce cooked appearance and lipid oxidation of barramundi fillet, two major drawbacks in pressurised fish muscle. Thus, HPP prior to freezing may be a good option for barramundi processors. Before chilled storage at 4 ± 1 °C, raw barramundi muscle was treated under 3 different conditions including pressurisation (HPP), chitosan coating and pressurisation (HC) and chitosan coating (CHI). Barramundi samples were investigated on day 1, 8, 15 and 23 during chilled storage. HPP at 200 MPa and 4 ± 1 °C for 3 min significantly improved texture profile, pH, drip loss and TVB-N of barramundi muscle as compared to CHI and control treatment. However, HPP did not delay microbial growth compared to CHI and control treatment. Application of HC treatment significantly hampered the development of TVB-N, microbial growth and improved texture and drip loss of barramundi muscle compared to control, HPP and CHI treatment. However, HC treatment resulted in a cooked appearance and acceleration of lipid oxidation, two major drawbacks in pressurised fish muscle. Pressurisation significantly decreased the activity of protease, but did not reduce the activity of LOX. Microscopic images also showed that the microstructures of pressurised samples were better preserved than the cracked microstructure of unpressurised samples. In this study, HPP was found to be the most favourable treatment for improving the quality of barramundi muscles stored in chilled condition for up to 23 days. For the application of HPP to produce barramundi gels, barramundi minced muscles with 1% and 2% added salt were pressurised at 300, 400 and 500 MPa at ≤ 10 °C and 50 °C for 10 min. Pressure induced barramundi gels (PG) exhibited a lower gel strength and poorer texture such as hardness and springiness as compared to conventional heat induced gels. Comparable water holding capacity to heat induced gels was only obtained at a salt concentration of 2% and at pressures ≥ 400 MPa. SEM images showed a compact network with smoother surface of barramundi minced muscle with 2% added salt and HPP at ≥ 400 MPa as compared to conventional heat induced gels. Gelling properties of barramundi minced muscle with 1.5% and 2 % added salt were assessed after HPP at 300, 400 and 500 MPa at 4 °C (initial temperature) for 10 min and subsequent cooking at 90 °C for 30 min. Whiteness, gel forming ability, water holding capacity, hardness and springiness of the barramundi gels increased as applied pressure and salt concentration increased. At 2% salt concentration, HPP resulted in barramundi gels with higher gel strength and smoother texture as compared to conventional heat induced gels (0.1 MPa, 90 °C for 30). At a reduced salt concentration (1.5%) and HPP at ≥ 400 MPa, the quality (gel strength, water holding capacity, hardness and springiness) of pressurised, cooked gels are comparable to those heat-induced gels with 2% added salt, but the microstructure is smoother. Scanning electron microscope images of pressurised, cooked gels showed a compact network with smoother surface than those of heat-only induced gels. Thus, application of HPP prior to cooking could be an effective method to enable reduced salt concentration in barramundi gels. Barramundi minced muscle with 1% and 2% added salt was gelled by different combinations of pressurisation (300, 400 and 500 MPa at 4 °C for 10 min), cooking (0.1 MPa, 90°C for 30 min) and setting (0.1 MPa, 50 °C for 2 h) to improve their mechanical properties and lower the amount of salt added to barramundi gels. At the low salt concentration of 1%, pressurisation prior to cooking (P - C) treatment resulted in barramundi gels with comparable mechanical properties and water holding capacity to those of conventional heat induced (HI) gels with 2% added salt. At a salt concentration of 2%, pressurisation prior to setting (P - S) and P - C gels exhibited higher mechanical properties and water holding capacity than HI gels. Scanning electron microscope images showed a smooth and dense microstructure of P - C and P - S gels, whereas the microstructure of HI gels is rough and less compact. P - S and P - C treatment can result in higher mechanical and functional properties of barramundi gels at conventional salt concentration (2%) compared to HI gels. P - C treatment can lower the salt concentration added to barramundi gels to 1% which is very significant for health-conscious consumers. To produce a shelf-stable barramundi product by high pressure thermal sterilisation (HPTS), barramundi muscle in a brine was treated at 600 MPa and three different temperatures (90, 110 and 120 °C) for 5 min. Barramundi muscle retorted at Fo = 3.38 was used as control. HPTS at 600 MPa and 110 °C and 120 °C, for 5 min, respectively, produced stable barramundi products, which were stored at room temperature and tested for up to 1 year. Hardness and springiness, of HPTS sterilised barramundi samples were enhanced (i.e. increased) compared to retorted samples. Gumminess, chewiness and cohesiveness of HPTS sterilised barramundi muscle were also similar to retorted samples and did not decrease as processing temperature increased. TBA and pH was also similar in all treatments, except for a significant increase of pH of samples treated at 600 MPa and 90 °C for 5 min after 3 months of storage. In general, HPTS could be a feasible option to produce a sterilised barramundi product with better overall quality and is recommended for more research on other HPTS barramundi products.
- Subject
- high pressure processing; barramundi; gel; freezing
- Identifier
- http://hdl.handle.net/1959.13/1354648
- Identifier
- uon:31320
- Rights
- Copyright 2017 Binh Truong
- Language
- eng
- Full Text
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