Fruit and vegetable processing generates large amounts of pomaces. Valuable compounds such as lipid, fiber, protein, and antioxidant can be recovered from these waste materials and converted into food ingredients. The main purpose of this dissertation project was to investigate chemical and nutritional characteristics of grape, tomato, and pomegranate processing byproducts and their potential usages as functional food ingredients through an integrative approach. The chemical compositions of raw pomaces were identified, and different methods for extracting the valuable components, lipids in particular, from the pomaces were investigated. The chemical and nutritional properties of lipids recovered with different methods were also compared. The results from the pomegranate study showed that high levels of oils and polyphenols were recoverable from the inedible portions of pomegranate fruits. Total oil contents in pomegranate seeds ranged from 15.23-21.32% (dry basis) and consisted of 81-84% punicic acid, 4-5% palmitic acid, 3-4% linoleic acid, 3-4% oleic acid, 3% ?-eleostearic acid, and 2-3% stearic acid. Total phenolic contents for the pomegranate peel soluble, peel insoluble, seed soluble, and seed insoluble fractions ranged from 146.29-279.32, 6.61-13.20, 5.86-9.04, and 4.28-6.19 mg gallic acid equivalent/g dry sample, respectively. Trolox equivalent antioxidant capabilities of the four fractions varied from 241.23-562.43, 17.40-26.51, 2.45-4.52, and 6.53-9.77 mg/g. In the recovery of functional components from the fruit pomaces, the mechanical pressing method could be used to extract grape, tomato, and pomegranate seed oils using appropriate expeller presses. A maximum oil extraction efficiency of 64.4% was attained in grape seed pressing when intact seeds with 5.3% moisture (d.b.) were pressed at 95 rpm using a 6 mm-die. Physiochemical properties of mechanically-pressed fruit seed oils were compared with oils produced from a conventional hexane extraction. The fruit seed oils were rich in unsaturated fatty acids, particularly linoleic, oleic, and punicic acids. Acid values of hexane-extracted oils and mechanical-pressed oils were 1.18±0.06 and 1.46±0.06 (grape), 0.57±0.00 & 0.85±0.01 (tomato), and 1.10±0.00 and 1.30±0.31 (pomegranate), respectively. Peroxide values were 2.42±0.14 and 15.50±0.25 (grape), 1.59±0.14 and 5.40±0.55 (tomato), and 3.90±0.32 and 6.77±0.37 (pomegranate). Iodine values were 126.77±2.60 and 136.81±6.67 (grape), 120.98±1.27 and 119.99±3.93 (tomato), and 147.32±3.60 and 163.39±5.25 (pomegranate). There were no significant differences in fatty acid compositions and initial oil qualities between oils obtained from different recovery methods. However, pressed oils retained more phenolic compounds and exerted higher antioxidant activities. Total phenolic content of pressed oils ranged from 11.94-54.87 mg gallic acid equivalent (GAE)/kg oil while the polyphenol concentrations of hexane-extracted oils only ranged from 6.85-18.18 mg GAE/kg oil. The recommended shelf lives of the grape, tomato, pomegranate seed oils, obtained either from pressing or solvent extraction, were 3, 6, and 24 months, respectively. Cholesterol-lowering effects of fruit seed oils and defatted pomegranate meals were studied in vivo using hamsters. Grape, tomato, and pomegranate seed oils were included in high-fat diets at 10, 10, and 3% (w/w) to partially substitute for butter, which was rich in saturated fats. Significant reductions in plasma triglycerides, low-density lipoprotein cholesterols, and the ratios of low-density lipoprotein to high-density lipoprotein were observed in the treatment diets. Fruit seed oils exhibited cardioprotective activities by lowering risk factors for heart diseases. Therefore, consumptions of grape, tomato, and pomegranate seed oils as parts of heart healthy diets are highly recommended. In conclusion, fruit seed oils recovered from fruit and vegetable processing waste exhibited great potentials to be repurposed into healthy and bioactive lipid sources.
|Commitee:||German, Bruce J., Upadhyaya, Shrinivasa K.|
|School:||University of California, Davis|
|School Location:||United States -- California|
|Source:||DAI-B 78/03(E), Dissertation Abstracts International|
|Keywords:||Cholesterol studies, Fruit seed oils, Mechanical pressing, Physiochemical properties, Pomace|
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