Tilapia are freshwater fish that have become important in aquaculture and as a stable global source of seafood due to their ability to thrive in different environments. However, tilapia are sometimes considered nutritionally undesirable due to their high n-6 to n-3 fatty acid ratios. A market study was conducted first to determine fatty acid compositions in tilapia fillets in different US markets. Then a research was conducted to enhance nutritional value of tilapia by improving the n-3 and oleic acid contents in fish fillets without compromising fish growth or feed conversion ratios. Feeds were formulated with combinations of high and low n-6, n-3, and oleic acid levels using soybean oil, fish oil, algae oil, and high-oleic sunflower oil. Then 12 diets, including a commercial diet, were assigned to 24 tanks, each with 25 tilapia per tank. A Recirculating Aquaculture System (RAS) was used to grow the fish for 8 weeks. Fatty acid compositions of tilapia fillets were determined and samples were vacuum packed and stored at -10oC and -20oC to test oxidative degradation and fatty acid compositional changes. The market survey data showed that there were significant differences in fatty acid composition, lipid content, and n-6:n-3 fatty acid ratios depending on the country of origin. Samples from USA had ideal n-6:n-3 ratios (1.3 ±0.85) while samples from Southeast Asia had higher n-6:n-3 fatty acids ratio (6.6 ±0.54). Algae oil incorporation significantly increased DHA level while fish oil incorporation significantly increased both EPA and DPA. High-oleic sunflower oil based diets improved oleic acid levels and reduced linoleic acid compared to the soybean oil based diets. Sensory evaluation indicated that lipid source did not significantly impact preference or overall fillet quality, including texture. Interestingly, a survey showed people were interested in value-added tilapia, and would pay up to 30% more for nutritionally enhanced fish compared to the $5.00/lb fresh fillet price currently available in supermarkets. There was no observable oxidation during long term frozen storage. The oxidation study proved that value-addition would not be compromised during the long term storage conditions, even under temperature abuse. It is possible to improve tilapia nutritional quality through diet to provide consumers with value-added products that maintain quality during frozen storage. / Ph. D. / Tilapia are high quality food with high levels of protein. However, many consumers are skeptical about tilapia due to their undesirable lipid composition containing high levels of omega 6. Therefore initially, the market study was developed to identify the lipid composition of tilapia US consumers were exposed to. Then the experiment was designed to create high omega 3 tilapia by improving the diets using mixture of fish oil, algae oil, high-oleic sunflower oil, and soybean oil. The 8 week tilapia growth trial was conducted with 12 experimental diets. Then the fish fillets were collected and analyzed for their fatty acid composition using GC/MS. Also fillet’s shelf-life study was conducted in 2 frozen storage conditions up to 9 months. The market study proved that the omega 6 to omega 3 ratio was favorable especially in USA sourced tilapia. However it also showed wide variation in omega 6 to omega 3 ratio depending on the country of origin. Tilapia from USA had an ideal omega 6:omega 3 ratio (1.3 ±0.85) while tilapia from Southeast Asia had higher omega 6:omega 3 ratio (6.6 ±0.54). The experimental study showed that the algae oil addition significantly improved DHA level while fish oil addition improved EPA and DPA. Higholeic sunflower oil addition improved omega 9 compared to the soybean oil based diets. Sensory evaluation indicated that different lipid sources had no impact on consumer preference. Interestingly, the survey showed that the people were interested in healthier tilapia, and were willing pay up to 30% more to the $5.00/lb of supermarket fresh fillet price. There was no observable degradation during long term frozen storage. The shelf life study proved that valueaddition would not degrade during the long term storage conditions. Therefore, development of high quality tilapia through diet manipulation is possible that does not degrade over 9 months of frozen storage.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/85868 |
| Date | 26 May 2017 |
| Creators | Chu, Hyun Sik Stephano |
| Contributors | Food Science and Technology, O'Keefe, Sean F., Kuhn, David D., Smith, Stephen A., Duncan, Susan E. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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