Date of Award
Master of Science (MS)
Food, Nutrition, and Culinary Science
McGregor , John U
Coffee , Aubrey
In this thesis, the potential for almond skins in their native state as a natural antioxidant in foods was explored. A literature review of general information on almonds, research done on almond skins, and general information on antioxidants is presented. The almond skins used in this study required an additional heat treatment step to improve their microbiological quality before further treatments and analysis could be performed. A descriptive analysis sensory panel was utilized to identify potential flavor and aroma descriptors and their intensities. The aroma descriptors identified were toasted, bran, and toasted; nutty. The flavor descriptors identified were toasted, bran, nutty buttery, and toasted; nutty. Proximate analysis, GC-MS headspace analysis, and total phenolic content of the almond skin were determined. Several aromatic compounds, including benzaldehyde and hexanal, were identified in almond skins via GC-MS analysis. Total phenolic content ranged from 5-6.1 quercetin equivalents per gram of almond skin. Soybean oil was treated with varying levels of almond skin and analyzed using the Oxidative Stability Index (OSI) as both an analytical method and oxidation chamber prior to other analyses. Peroxide values and GC-MS headspace analysis was done on the treated soybean oil as well. BHA was also used as a control treatment to serve as a comparison. Measures of oxidative stability of the treatments varied depending on the analysis used. The OSI analysis did not show any differences between treatments (p>0.05); however, peroxide values of treated oil samples were lower than those of the control oil samples after 6.5 hours of oxidation (p>0.05). GC-MS analysis showed that hexanal concentrations of almond skin treated oil oxidized for 3.25 hours were greater than those of control and BHA treated oil (p>0.05). Results from this study demonstrate the critical need for a thorough review of current processing and handling procedures to improve the microbiological quality of commercial almond skins. Elimination of the additional heat treatment step that was employed to improve the microbiological quality of the almond skins would likely allow for the identification of new sensory descriptors. Peroxide values remain good indicators of oxidation and should be taken at more intervals to allow for better detection of differences between treatments. Normally, hexanal is a good indicator of oxidation; however, the almond skins in this study contained hexanal before treatment. Analysis of more varieties and samples of almond skins should be done to determine good markers of oxidation. Use of varieties of almond skins known to be high in phenolic content should be further explored before eliminating almond skins as a natural antioxidant source for foods.
Johnson, Heather, "Almond Skins as a Natural Antioxidant" (2007). All Theses. 163.