The overall baseline (as received) moisture, protein and fat content of hybrid catfish (Ictalurus furcatus x Ictalurus punctatus) fillets were 77.8 +/- 1.38%, 16.7 +/- 0.50% and, 5.7 +/- 1.6%, respectively. Small fillets (111 +/- 19 g) had higher (P≤0.05) baseline moisture (78.6 +/- 0.87% vs 76.8 +/- 1.15%) and lower (P≤0.05) fat content (4.7 +/- 0.64% vs 6.8 +/- 1.72%) than large fillets (247 +/- 62 g), whereas protein content was similar (P>0.05) for both sizes. Retained water of the final fresh and frozen fillets was 1.2 +/- 2.03% and 3.1 +/- 1.02%, respectively, irrespective of fillet size. Psychrotrophic (PPC) and total coliform plate counts (TCC) of the baseline fillets were 4 log CFU/g and 1.6 log CFU/g, respectively and were not different between the process steps, except after injection which was higher (P>0.05) than baseline. Moisture-protein ratio and fat content were good (P≤0.05) predictors for retained water in catfish fillets during processing.

(Piaractus mesopotamicus) initially weighing 72.0 g were fed three diets - a) 0.5% vegetable (zucchini), b) commercial 32% (P32) and c) commercial 36% (P36) protein diets for 24 weeks and their growth performance compared. Processing yields and proximate composition were determined following dressing of pacu. The microbiological quality of pond cultured pacu was compared to aquacultured hybrid striped bass, tilapia, and rainbow trout grown in pond and recirculating aquaculture systems. Sensorial analyses for differences in flavor, preference, and color were also determined. Protein concentration significantly influenced the weights, lengths, specific growth rate, feed conversion ratio, and protein efficiency ratio (p < 0.05). Diet insignificantly influenced the processing yields (p > 0.05). The moisture, protein and total lipid contents were significantly affected (p < 0.05) by the dietary protein. The indicative bacterial quality differed significantly for pacu as well as the water used for culturing pacu (p < 0.05) among dietary treatments. Aquaculture production systems significantly influenced the indicative and pathogenic bacterial quality. Listeria monocytogenes, Salmonella spp., Yersinia enterocolitica, and Escherichia coli O157:H7 were not isolated from any of the sampled fish. The qualitative and quantitative results of Clostridium botulinum were influenced by the production system (p < 0.05). Flavor of pacu was comparable to that of hybrid striped bass, tilapia, and rainbow trout, but superior to catfish. Cooking significantly improved the color of the ground fish fillets. / Master of Science

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2008. / Härtill 5 uppsatser.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniversitet, 2004. / Härtill 5 uppsatser.

Pacific bluefin tuna (PBT; Thunnus orientalis) has grown significantly in popularity in recent years due to the globalization of Japanese cuisine. PBT is highly sought after for sushi and sashimi products due to its great quality and taste. Wild populations of this species have been affected by their increasing popularity, pushing innovators in the food industry to create meat alternative versions of PBT. The muscle composition of PBT varies, leading to different types (cuts) of meat in a way that is analogous to various cuts of beef. This study evaluated the differentiation amongst the 6 distinct cuts, including otoro, ventral akami, dorsal akami, ventral chu-toro, dorsal chu-toro, and wakaremi conducting volatile analysis, proximate analysis, and fatty acid analysis. The results from these analyses can then be used as a base standard for companies seeking to create alternatives versions of PBT. Samples analyzed in this study were cultured PBT species that were caught as juveniles and raised in captivity on a PBT farm in Mexico. Volatile analysis was conducted using a SPME GC/MS method. Overall, 41 aroma compounds were identified in PBT that met the identification criteria, including 9 aldehydes, 7 alcohols, 14 alkanes, 2 ketones, 4 alkenes, 3 aromatic compounds, and 2 miscellaneous compounds. Proximate analyses were conducted using standard methods. Significant differences (p <0.05) were found between each cut for the proximate analysis. The fatty acid analysis determined that there were twenty-two identifiable fatty acids found in the different cuts. The omega-3 fatty acids eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) with DHA being present at a higher amount than EPA in each cut. Overall, there are similarities and differences among the different cuts of bluefin tuna that researchers would need to mimic to provide adequate nutritional and sensorial properties of PBT. / Master of Science in Life Sciences / Pacific bluefin tuna (PBT; Thunnus orientalis) is a fish that has gained tremendous popularity over the years due to the globalization of Japanese cuisine. This tuna species is synonymous with high quality and great taste, making it key for sushi and sashimi dishes. The increased demand for this species has caused wild populations to decrease; therefore, the food industry has sought to create meat alternatives for the species. The PBT has 6 distinct cuts that make up the composition of the fish, similar to the differences that can be found in beef cuts. These 6 distinct cuts are otoro, ventral akami, dorsal akami, ventral chu-toro, dorsal chu-toro, and wakaremi. The purpose of this study is to determine the aroma composition, fatty acid composition, and fat, moisture, ash, and protein contents of the different cuts. To measure the aroma composition, gas-chromatography mass spectroscopy (GC-MS) was used; it is a machine that can be used to identify and measure the aroma compounds of products. Standard procedures were used for the other analyses. Overall, 41 aroma compounds were identified in PBT that met the identification criteria, consisting of aldehydes, alcohols, alkanes, ketones, alkenes, aromatic compounds, and some miscellaneous compounds. The cuts displayed distinguishable differences in their fat, ash, moisture, and protein contents. The fatty acid analysis concluded that there were twenty-two identifiable fatty acids found in the different cuts. In this study, close attention was paid to omega-3 fatty acids due to their health benefits for consumers. The omega-3 fatty acids eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) were found in all cuts with DHA being present at a higher amount than EPA in each cut. From this study, researchers have the foundation for understanding the composition of PBT to create a meat alternative that meets consumer expectations.

Condition indices are widely used to generate biological insight. However, purported relationships to indices are imprecise or inconsistent in the wild. I investigated factors influencing relative weight (Wr), a condition index commonly applied to fish. I first examined the relationship of Wr to physiology in two bluegill Lepomis macrochirus populations over a year. I regressed tissue composition (percentages of lipid, protein and water) and organ indices (liver-, gonad-, and viscerosomatic indices) on Wr. The regression model had little explanatory power (adjusted R2 = 0.14). Lipid was most influential (partial R2 = 0.11), but correlation strength fluctuated by season and population. To test the generality of these results, I performed a similar regression on a bluegill population with higher average Wr. Again, variables were not well correlated to Wr (adjusted R2 = 0.13). Combining comparable data sets increased Wr range 64% but explanatory power was low (adjusted R2 = 0.41) Both studies showed that expected correlations of physiological variables to Wr can be confounded in natural environments. To examine differences between natural and laboratory environments, I manipulated initial Wr and ration of juvenile bluegills. Although organ indices and tissue composition of all groups changed in time ((Wilks' Δ > 0.387, P > 0.03), no temporal pattern matched to Wr. At termination, all variables showed high correlations to Wr (r2 > 0.64). Correlation strength increased with time in the laboratory. Both ration and environment influenced correlations. Lastly, I examined differences in interpretation of Wr for chain pickerels Esox niger, largemouth bass Micropterus salmoides, and black crappies Pomoxis nigromaculatus. Regression models were compared to concurrent bluegill models. Piscivore models fit well (adjusted R2 > 0.50), whereas bluegill models had the lowest explanatory power (adjusted R2 = 0.13 and 0.14). Ecological specialization affected correlations to Wr. Theoretically, condition index values are determined by resource acquisition versus expenditure. Exact physiological expression is determined by life history and performance. Condition indices are imprecise predictors but track net somatic investment with great generality. Ancillary data, such as growth or length-at-maturity, may clarify interpretation. Condition indices should be used as qualitative monitoring tools, not omnibus physiological predictors. / Ph. D.

The reliable measurement of growth and condition is vital for effective fisheries assessments. Biologists have long attempted to estimate condition for their assessments, but a reliable method to nonlethally estimate body composition is lacking. Proximate analysis is the most dependable and accurate method for estimating internal composition, but it is lethal, time consuming, and expensive. Recent research has shown bioelectrical impedance analysis (BIA) to be an effective method for estimating proximate composition in some fishes. The technique is quick, inexpensive, and, most importantly, nonlethal, which is vital when examining endangered species or cultured fish. My research focused on developing BIA indices for several new species of fish, using those indices to evaluate the body composition of fish in the field, and determining whether water temperature influenced resistance and reactance measurements. I found that BIA accurately estimated the body composition of bluegill Lepomis macrochirus, redear sunfish Lepomis microlophus, brook trout Salvelinus fontinalis, and northern logperch Percina caprodes (r2 ≥ 0.71, p < 0.0001). I also determined that bluegill and redear regressions were not significantly different (P ≥ 0.10) suggesting they can be used interchangeably during future studies. Laboratory studies revealed that water temperature did not significantly influence resistance and reactance measurements of bluegill, redear, and largemouth bass Micropterus salmoides (P ≥ 0.18). These results, along with previous literature, indicate that BIA may be an accurate and reliable assessment tool for fisheries biologists. / Master of Science

Rockfish are commercially and recreationally important, yet due to the in habitat depths at which rockfish inhabit, little is known about their ecology. As a consequence, management of rockfish population as a fishery resource is a work in progress. In particular, changes in physiological condition aver the course of the year is poorly described. This study examined 19 different species of Sebastes from the Southern California Bight over four seasons (late summer, fall, winter, and spring) using metabolic enzyme assays. Enzymes used were lactate dehydrogenase (LDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and citrate synthase (CS). Some muscle composition data (percent water, percent protein, percent lipid, and protein as a percentage of wet mass) were also used to help interpret the enzyme data. Enzyme activity was lowest in the summer when expressed as activity per gram wet weight but when it was expressed per gram protein the trend was reversed. We found that the rockfish tend to have the highest protein as a percentage of wet mass (P%WM) in the spring right before the upwelling period begins and have the lowest P%WM in late summer after the peak of upwelling. Their metabolic poise (represented as CS/LDH) grouped according to locomotory habit (benthic or bentho-pelagic). A mass and oxygen consumption plot also showed that the species group according to locomotory habit. With those known to be benthic grouped together and those species that are known to more actively swimming had higher values. This knowledge could be used to infer whether a rockfish that hasn't been well studied is benthic or bentho-pelagic.

Wheat distillers dried grain with solubles (DDGS) is a co-product of ethanol production, primarily utilized as an animal feed ingredient. Reduced protein quality, a highly energy-intensive drying process, and product variability are some of the challenges that currently confront its production in western Canada. The main focus of this research undertaking was to examine, on a laboratory-scale, the effect of condensed distillers solubles (CDS) : wet distillers grain (WDG) blending ratio and drying conditions on the protein quality and physico-chemical characteristics of wheat DDGS. The potential of microwave-based drying methods in minimizing protein damage and energy consumption was investigated. An auxiliary case study was also conducted in the Philippines to apply the knowledge and skills acquired from the PhD research undertaking to a related problem situation in a developing country. It aimed to provide more information about brewers spent grain (BSG) supply and utilization in Misamis Oriental, Philippines and enhanced the efficiency and safety of BSG utilization as an animal feed ingredient. Laboratory-scale investigations used samples produced at three CDS:WDG blending ratios (by mass): 15:85 (15% CDS), 30:70 (30% CDS), and 45:55 (45% CDS) and dried under forced air convection (40-120C), and under microwave (420 – 805 W) and microwave convection (nominal settings of 130C-30% power to 190C-30% power) methods using a domestic microwave oven. Freeze-dried samples were used as standards in evaluating chemical composition and color of wheat DDGS. As CDS level in the blend was increased, protein and ash content of freeze-dried samples increased while fat, acid detergent fiber (ADF) and neutral detergent fiber (NDF) content decreased. These trends were attributed to proximate composition differences between CDS and WDG fractions. The CDS fraction had higher protein and ash and lower fat, ADF, and NDF contents compared to WDG. Variation in the CDS:WDG blending ratio employed in the source ethanol plant could be one of the factors contributing to the observed proximate composition differences between two ethanol plant-sourced wheat DDGS samples. This was verified through proximate analyses of: (i) plant-sourced wheat DDGS samples from two production batches; (ii) CDS and WDG samples obtained on the same production date; and (iii) laboratory-produced wheat DDGS samples at varying CDS:WDG blending ratios. Protein, ash, and NDF contents of forced-air convection-, microwave-, and microwave convection-dried samples also showed strong linear relationships with CDS level. Fat and ADF content, however, did not exhibit similar strong relationships with CDS level, indicating the influence of drying conditions. Maximum lysine and minimum acid detergent insoluble crude protein (ADICP) contents were achieved in blends with the highest CDS level (45% CDS) and dried under lower drying temperature (80C), microwave power (676 W), and microwave convection (150C-30% power) settings. Microwave- and microwave convection drying achieved desirable protein quality associated with lower temperature drying under much shorter times. Laboratory-scale drying of ethanol plant-sourced wet distillers grain with solubles (WDGS) under forced air convection produced DDGS samples with decreased lysine content as drying air temperature was increased. In terms of physical properties, dried samples with higher CDS level were significantly finer, denser, less flowable, less dispersible, have lower thermal diffusivity and higher internal friction coefficients, and produced denser and stronger pellets. Color parameters of freeze-dried samples were significantly affected by CDS level. As CDS level increased, lightness (Hunter L) decreased while redness (Hunter a) increased. The color parameters of forced-air convection-, microwave-, and microwave convection-dried DDGS samples did not, however, exhibit similar linear trends with CDS level as these were also affected by drying conditions, such as drying air temperature and microwave power level. Effective moisture diffusivity values, estimated from the drying data, were also significantly affected by drying conditions (drying air temperature and microwave power levels), CDS level, and interaction between drying air temperature and CDS level. Effective moisture diffusivity decreased as CDS level was increased. Physical properties of two commercial (ethanol plant-sourced) wheat DDGS samples, as affected by moisture content, were also assessed. Techno-economic evaluation results indicated that complete replacement of the conventional hot air drying with microwave drying technology was not yet economically feasible. Although energy consumption during drying was substantially reduced with the use of microwave energy, the cost of electricity to generate microwave energy was high. Incorporating microwave drying toward the end of the hot air drying process was seen as the more economically viable alternative. Drying of BSG was not commonly practiced in Misamis Oriental, Philippines. The material was typically stored in open concrete bins and commonly fed to dairy cattle in its wet form. A prototype batch dryer, powered either by solar or biomass energy, was developed to improve shelf life and safe use of BSG. Initial tests showed that drying spent grain using a biomass furnace was feasible. Operating the dryer using solar energy was not an attractive option because of the long drying time. Basic physical attributes, proximate composition, and moisture sorption characteristics of the dried BSG were also determined. Practical implications of the results of these two studies to their respective local contexts were discussed. Recommendations to further improve understanding of wheat DDGS protein quality and physico-chemical characteristics, BSG dryer performance, backyard farmers’ sustainable access and safe use of BSG were also presented.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2002. / Härtill 4 uppsatser.