The production of volatile off-flavor compounds by lipid autoxidation is a major quality concern in foods. Photosensitizers such as chlorophyll can produce highly reactive singlet oxygen, thereby accelerating oxidation reactions. The objective of this research was to determine the effect of chlorophyll concentration on the production of volatile compounds in soybean oil, peanut oil and lard. Headspace volatile compounds were collected by solid phase microextraction and analyzed by gas chromatography and mass spectroscopy. The amounts of pentane, pentanal, 1-pentenol, 2-pentenal, hexane, 1-hexene, 2-hexanal, heptanal, 2-heptenal, 2-pentyl furan, 2,4,-heptadienal, 2,4-nonadienal, 1-octen-3-ol and 2-octenal were significantly affected by chlorophyll concentration with 1 to 2 days of light exposure. Relative to the triplet oxygen product hexanal, the singlet oxygen product 2-heptenal increased in quantity rapidly in soybean oil or peanut oil containing 5 ppm or 10 ppm chlorophyll when exposed to light even at 4 °C. The presence of chlorophyll was the most significant factor to the amount of volatile compounds during the first 2 days of light exposure; however, temperature was the most significant factor after 2 days of light exposure. Orange juice is the most predominant fruit juice in the U.S. market. Commercial orange juice is thermally processed to inactivate pectinmethylesterase (PME) and spoilage organisms. However, thermal processing can be detrimental to the flavor and nutritional qualities of the juice. High pressure processing (HPP) is a non-thermal processing method that can inactivate enzymes and undesirable microorganisms. The presence of CO2 in orange juice during HPP had been shown to enhance the inactivation of undesirable microorganisms. The effects of HPP, CO2-assisted HPP, and thermal processing on the inactivation of PME, volatile compound retention and ascorbic acid retention in Valencia orange juice was evaluated over 4 months of storage at 4 and 30 °C. Pressure magnitude, temperature, and dwell time were significant factors in the inactivation of PME. Pressure treatments resulted in insignificant volatile losses and <10% ascorbic acid reduction. The HPP+CO2 juice had the greatest cloud stability and highest ascorbic acid retention during storage. HPP+CO2 produced a cloud-stable orange juice with more ascorbic acid and flavor volatiles than the thermally processed juice. o The production of volatile off-flavor compounds by lipid autoxidation is a major quality concern in foods. Photosensitizers such as chlorophyll can produce highly reactive singlet oxygen, thereby accelerating oxidation reactions. The objective of this research was to determine the effect of chlorophyll concentration on the production of volatile compounds in soybean oil, peanut oil and lard. Headspace volatile compounds were collected by solid phase microextraction and analyzed by gas chromatography and mass spectroscopy. The amounts of pentane, pentanal, 1-pentenol, 2-pentenal, hexane, 1-hexene, 2-hexanal, heptanal, 2-heptenal, 2-pentyl furan, 2,4,-heptadienal, 2,4-nonadienal, 1-octen-3-ol and 2-octenal were significantly affected by chlorophyll concentration with 1 to 2 days of light exposure. Relative to the triplet oxygen product hexanal, the singlet oxygen product 2-heptenal increased in quantity rapidly in soybean oil or peanut oil containing 5 ppm or 10 ppm chlorophyll when exposed to light even at 4 °C. The presence of chlorophyll was the most significant factor to the amount of volatile compounds during the first 2 days of light exposure; however, temperature was the most significant factor after 2 days of light exposure. Orange juice is the most predominant fruit juice in the U.S. market. Commercial orange juice is thermally processed to inactivate pectinmethylesterase (PME) and spoilage organisms. However, thermal processing can be detrimental to the flavor and nutritional qualities of the juice. High pressure processing (HPP) is a non-thermal processing method that can inactivate enzymes and undesirable microorganisms. The presence of CO2 in orange juice during HPP had been shown to enhance the inactivation of undesirable microorganisms. The effects of HPP, CO2-assisted HPP, and thermal processing on the inactivation of PME, volatile compound retention and ascorbic acid retention in Valencia orange juice was evaluated over 4 months of storage at 4 and 30 °C. Pressure magnitude, temperature, and dwell time were significant factors in the inactivation of PME. Pressure treatments resulted in insignificant volatile losses and <10% ascorbic acid reduction. The HPP+CO2 juice had the greatest cloud stability and highest ascorbic acid retention during storage. HPP+CO2 produced a cloud-stable orange juice with more ascorbic acid and flavor volatiles than the thermally processed juice.