Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 87-109). Also available in print.

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Celiac disease is characterized by an allergic reaction to gluten that causes inflammation of the small intestine and can lead to malabsorption and malnutrition. Glutenree products are being developed that meet dietary needs of individuals with celiac disease. However, these products often lack whole grains and fiber. Fortification of glutenree products with flax can increase nutritional value and alleviate inflammation. Sensory analysis (N=152) was conducted to evaluate the acceptability of glutenree muffins with moderate (3.8%) and high (7.4%) amounts of added flax. Results indicated that consumers preferred (p<0.05) the muffin without flax or the highlax muffin more than the muffin with the moderatelax treatment. The highlax and control treatments were rated 6.7, between like slightly and moderately like; the muffins from the moderatelax treatment were rated 6.4 on a nine-point hedonic scale. Producers of glutenree products could potentially formulate muffins that include flax and are acceptable to consumers.

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Tree peony is known worldwide for its excellent ornamental and medical values, but recent reports that their seeds contain over 40% α-linolenic acid (ALA), an essential fatty acid for humans drew additional interest of biochemists. To understand the key factors that contribute to this rich accumulation of ALA, we carried out a comprehensive study of oil accumulation in developing seeds of nine wild tree peony species. The fatty acid content and composition was highly variable among the nine species; however, we selected a high- (P. rockii) and low-oil (P. lutea) accumulating species for a comparative transcriptome analysis. Similar to other oilseed transcriptomic studies, upregulation of select genes involved in plastidial fatty acid synthesis, and acyl editing, desaturation and triacylglycerol assembly in the endoplasmic reticulum was noted in seeds of P. rockii relative to P. lutea. Also, in association with the ALA content, transcript levels for fatty acid desaturases (SAD, FAD2 and FAD3), which encode for enzymes necessary for polyunsaturated fatty acid synthesis were higher in P. rockii compared to P. lutea. We further showed that the overexpression of PrFAD2 and PrFAD3 in Arabidopsis increased linoleic and α-linolenic acid content, respectively and modulated their final ratio in the seed oil. In conclusion, we identified the key steps that contribute to efficient ALA synthesis and validated the necessary desaturases in P. rockii that are responsible for not only increasing oil content but also modulating 18:2/18:3 ratio in seeds. Together, these results will aid to improve essential fatty acid content in seeds of tree peonies and other crops of agronomic interest.

The increasing need for healthy edible oil has driven us to identify α-linolenic acid (ALA)-rich species and identify key biochemical steps in ALA synthesis. Seeds of tree peony species are rich in unsaturated fatty acid content with > 40% ALA in the total fatty acid. However, fatty acid content and composition is variable among the tree peony germplasm. To this extent, a comparative study was carried out to identify the key genes responsible for differential oil accumulation among nine wild tree peony species. Subsequent to analyzing fatty acid content and composition of the seeds from nine tree peony species, a high- (P. rockii) and low-oil (P. lutea) accumulating species were selected for transcriptome analysis. Gene expression analysis revealed upregulation of select genes involved in plastidial fatty acid synthesis, and acyl editing, desaturation and triacylglycerol assembly in the endoplasmic reticulum in seeds of P. rockii relative to P. lutea. Also, in association with ALA content in seeds, transcript levels for fatty acid desaturases (SAD, FAD2 and FAD3), which encode for enzymes necessary for polyunsaturated fatty acid synthesis were higher in P. rockii compared to P. lutea. Additionally, we showed that the overexpression of PrFAD2 and PrFAD3 in Arabidopsis increased linoleic and α-linolenic acid content, respectively and modulated their final ratio in the seed oil. In conclusion, we identified the key steps that contribute to efficient ALA synthesis and validated the necessary desaturases in P. rockii that are responsible for not only increasing oil content but also modulating 18:2/18:3 ratio in seeds. Together, these results will aid to improve essential fatty acid content in seeds of tree peonies and other crops of agronomic interest.

The antioxidants BHA, BHT, and ascorbic acid were added to flaxmeal breads to prevent rancidity. Six types of yeast leavened breads were evaluated: control (100% bread flour), flaxmeal (15%) bread, and flaxmeal (15%) bread that contained 0.01% respectively of BHA, BHT, BHA and BHT, and ascorbic acid. Vital wheat gluten was added in all the flaxmeal breads. Chemical, objective and sensory tests were used to evaluate the breads. The crumb texture of all the experimental breads was significantly softer (p¡à 0.05) than the control breads, but the control breads were significantly moister (p¡à 0.05) than the flaxmeal breads that contained BHA and BHT, separately. No significant differences (p>0.05) were found in loaf volume of the control bread and the experimental breads. The crumb color of the experimental breads was significantly darker (p<0.0001) due to the incorporation of flaxmeal. The acid value of the flaxmeal breads was significantly higher (p¡à 0.05) than the control breads. No significant differences (p>0.05) were found in peroxide values between the control breads and experimental breads after eight weeks. The QDA sensory tests showed that breads containing BHA or in combination with BHT were moister, chewier and had the least noticeable stale taste when compared to the control breads. Ascorbic acid was not as effective as BHA or a combination of BHA and BHT in preventing lipid oxidation, but produced the softest bread. This study showed that flaxmeal breads made with BHA and BHT provided the best protection against lipid oxidation and produced a moist and chewy bread. / Master of Science

Beginning January 1, 2006 the U.S. Food and Drug Administration mandated that the amount of trans fats per serving be listed on the Nutrition Facts panel. Consequently new soybean breeds that would no longer be subject to the hydrogenation process, thus reducing trans fats, were developed. By traditional plant breeding techniques, plant breeders have developed a low linolenic soybean with 83.36% less alpha-linolenic acid (ALA; omega-3) than conventional soybean. A number of studies have demonstrated that the influence of dietary fats on cancer depends on the quantity as well as the type of lipids and diets with a disproportionately high omega-6 (n-6)/omega-3 (n-3) ratio are thought to contribute to cardiovascular disease, inflammation and cancer. Conventional soybean oil (SO) has an n-6/n-3 ratio of 8/1 while the new low linolenic soy bean oil (LLSO) has an n-6/n-3 ratio of 56/1. In this study, we evaluated the effects of dietary LLSO, SO and lard on the progression of breast cancer (BC). Thirty-five, 6-wk old, ovariectomized, athymic mice received human pre-malignant breast cells (MCF-10AT1 1 x 105 cells/40μl/ Matrigel/spot, 4 spots/mouse). Mice were divided into three groups and then fed isocaloric and isonitrogenous diets with disparate fat sources: LLSO (20% of total energy intake), SO (20%) and lard (20%). The dietary treatment lasted 24 weeks upon which the study was terminated and tumors, tissues and blood samples were analyzed. Average tumor surface area at termination for the LLSO group was 45.11 ± 4.46 mm2, 40.08 ± 4.2 mm2 for lard and 56.63 ± 5.42 mm2 for SO. Messenger RNA (mRNA) expression of HER2/neu, epidermal growth factor receptor (EGFR), H-ras, Bcl-2, cyclooxygenase-2 (COX-2), vascular epidermal growth factor (VEGF), and fatty acid synthase (FAS) in tumors were analyzed using quantitative real time-polymerase chain reaction (qRT-PCR). We found that dietary LLSO supplementation significantly (p < 0.05, Tukey's test) increased tumor expression of oncogenes HER2/neu, EGFR, FAS, and H-ras, but not in the SO or lard supplemented groups. Relative mRNA expression was also significantly increased in both LLSO and SO groups, however, there was no marked difference in mRNA expression for Bcl-2 and COX-2. Removed tumors were evaluated microscopically for histologic lesion progression corresponding to human breast cancer progression. Tumors from the LLSO group showed more advanced lesions (grade 2) (p < 0.05, Chi Square test) with areas of four or more layers of epithelial cells and irregularly shaped lumens. These data suggest that dietary intake of LLSO may accelerate mammary tumor progression at a faster rate than conventional SO or lard. / Master of Science

Dietary fat has long been implicated in the etiology of metabolic and cardiovascular disease, and both the amount of fat and the fatty acid composition of the diet play a role in disease progression. Although national health organizations have set guidelines for the recommended intake of dietary fats, questions remain regarding the optimal dietary lipid profile for maintaining health and improving disease conditions. Whether certain types of fatty acids from plant-based oils can improve metabolic and vascular disease has been studied and debated, but not fully determined. In this study, we investigated the role of dietary fatty acids from plant-based oils, and examined their effects on metabolic and vascular disease parameters. Obese fa/fa Zucker rats were fed a diet containing flaxseed oil, which resulted in smaller adipocytes and decreased adipose tissue T-cell infiltration. Obese-prone Sprague Dawley rats were fed high-fat diets with different proportions of mono- and polyunsaturated fats. Changes were observed in adipose tissue levels of fatty acid synthase, adiponectin and fatty acid receptors GPR41 and GPR43, but other metabolic and inflammatory mediators in adipose tissue and serum remained stable. A systematic review and meta-analysis on the impact of n3 fatty acids on major cardiovascular endpoints showed that little evidence exists to support their role in peripheral arterial disease. Then again, very few studies on this topic have been conducted. To address this research gap, a clinical trial was designed to investigate the effects of a dietary intervention on blood vessel properties in people with peripheral arterial disease. Participants in the Canola-PAD Study consumed 25 g/day of canola oil or a Western diet oil mixture as part of their usual diet for 8 weeks. Although the intervention altered phospholipid fatty acids, vascular function, the lipid profile and inflammatory markers stayed relatively stable. Overall, this research demonstrates that dietary fatty acids from plant-based oils can be immunomodulatory, but at the physiological doses tested they are not potent mediators of functional changes in obesity or vascular physiology. / October 2015

The increasing demand for healthy edible oil has generated the need to identify promising oil crops. Tree peony (Paeonia section Moutan DC.) is a woody oil crop with α-linolenic acid contributing for 45% of the total fatty acid (FA) content in seeds. Molecular and genetic differences that contribute to varied FA content and composition among the wild peony species are however, poorly understood. Analyses of FA content and composition during seed development in three tree peony species (P. rockii, P. potaninii, and P. lutea) showed varied FA content in the three species with highest in P. rockii, followed by P. potaninii, and P. lutea. Total FA content increased with seed development and reached its maximum in its final stage. Seed FA composition analysis of the three species also revealed that α-linolenic acid (C18:3) was the most abundant, followed by oleic (C18:1) and linoleic (C18:2) acids. Additionally, quantitative real-time RT-PCR analyses of 10 key seed oil synthesis genes in the three tree peony species revealed that FAD3, FAD2, β-PDHC, LPAAT and Oleosin gene expression levels positively correlate with total FA content and rate of accumulation. Specifically, the abundance of FAD3 transcripts in P. rockii compared with P. potaninii, and P. lutea suggests that FAD3 might play in an important role in synthesis of α-linolenic acid via phosphatidylcholine-derived pathway. Overall, comparative analyses of FA content and composition in three different peony species revealed correlation between efficient lipid accumulation and lipid gene expression during seed development. Further characterization and manipulation of these key genes from peonies will allow for subsequent improvement of tree peony oil quality and production.