Frying oils and human health: Foods have been deep fried in fats and vegetable oils for centuries – the process rapidly cooks the food and can significantly enhance the flavor. However, many decades of nutrition and health research have helped us better understand which fats and oils are healthy and which are not. The chemistry: The majority of lipids in the vegetable oils that are used for deep frying are triglycerides which are comprised of a glycerol molecule esterified to three fatty acids. Fatty acids all have a long carbon chain with a terminal carboxyl group. The fatty acids components of triglycerides can either be saturated,(fully hydrogenated) or they may contain double bonds (unsaturated). The naturally occurring unsaturated fatty acids are also almost all in what is called the cis configuration (hydrogen atoms oriented on the same side of the carbon-carbon double bond). Hydrogenation: Saturated fatty acids have higher melting points than unsaturated fatty acids with a similar size, and thus were considered better for deep frying. But, many years of research indicated that saturated fats cause an increase in LDL cholesterol. This led the food industry to switch to hydrogenated fats that were solid at room temperature, and eliminated of the most unsaturated fatty acids. However, the discovery that the trans fatty acids formed during hydrogenation increased LDL cholesterol and also decreased the “good" HDL cholesterol. These discoveries in recommendations for dietary fats over the past several decades led to consumer confusion over which fats are healthiest. Hydrogenation and trans fatty acids are no longer acceptable. Polyunsaturated fatty acids: Polyunsaturated fatty acids (PUFAs), including the 18-carbon atom linoleic and linolenic acids, contain more than one carbon-carbon double bond, are present in significant quantities in many vegetable oils. They are often referred to as essential fatty acids since they are precursors required for our bodies to produce the 20-carbon atom arachidonic acid. This PUFA is the precursor of prostaglandins that are centrally involved in regulating many processes in our bodies. However, the same PUFAs are more readily oxidized and degraded by the high temperatures involved in deep frying than unsaturated or monounsaturated fatty acids such as oleic acid. In contrast, vegetable oils high in monounsaturated fatty acids - including safflower, sunflower and high oleic soy and Canola oils – are healthier and degrade more slowly. Deep Frying Byproducts: The rate of oxidative degradation of frying oils depends on the oil type, its surface/volume ratio, temperature, heating process, the food and the its immersion and even the characteristics of the frying container. Extended exposure of oil to high temperatures and air can generate highly oxidized, potentially toxic products. Deep frying conditions cause triglycerides to hydrolyze – freeing the fatty acids from the glycerol backbone. The fatty acids, especially the carbon-carbon double bonds of unsaturated fatty acids are then oxidized yielding a large number of aldehydes, ketones, epoxides. Some of these byproducts including trans fatty acids, hydroxylinoleic acid, and acrylamide are well known health hazards. Tracking Fry Oil Degradation: Efforts to monitor frying oil degradation have included a range of approaches, including observing the color of the oil, smoking, foaming and the taste of the food products, etc. Many of these are subjective. For example, the smoke point has several limitations when it comes to choosing the right oil for cooking. Some are highly unstable some cooking oils can have relatively high smoke points but still aren't suitable for high-heat cooking. After decades of research, measurements of Total Polar Compounds (TPC) are now accepted as the most reliable measure of oil quality. Measuring the concentration of TPCs is the best indicator for determining oil degradation. Healthy regulations: Although there is not one specific worldwide regulation for frying oil quality, many countries have guidelines or regulations restricting how much frying oil can be repeatedly used. These rules are based on extensive studies of frying oil stability during cooking and the generation of byproducts with deleterious effects in human health. Even in countries such as the USA and Australia, where TPC is not regulated, it is increasingly being used by foodservice operators as a benchmark for determining when to dispose of frying oil. The specific upper limit for TPC in frying oils used in food service for several countries are listed below.

Publications on the health hazards of used frying oil

Q. Zhang, A.S.M. Saleh, J. Chen and Q. Shen. Chemical alterations taken place during deep-fat frying based on certain reaction products: A review. Chemistry and Physics of Lipids, 2012, 165, p. 662– 681, 2012. J.B. Riera and R. Codony, Report Title: “Recycled Cooking Oils: Assessment of risks for public health.” Department of Nutrition, University of Barcelona, Spain European Parliament Directorate General for Research Directorate A. The STOA Programme, September 2000. A. Sebastian, S.M. Ghazani and A. G. Marangoni, Quality and safety of frying oils used in restaurants. Food Research International, 64, p. 420–423, 2014. H.H. Hosseini, M. Ghorbani and N. Meshginfar. A Review on Frying: Procedure, Fat, Deterioration Progress and Health Hazards, Journal of the American Oil Chemists’ Society, 93, p. 445–466, 2016. F. Lu, X. Wu, China food safety hits the “gutter”. Food Control, 41, p. 134-138, 2014.

Health Concerns

Health Concerns
Frying oils and human health: Foods have been deep fried in fats and vegetable oils for centuries – the process rapidly cooks the food and can significantly enhance the flavor. However, many decades of nutrition and health research have helped us better understand which fats and oils are healthy and which are not. The chemistry: The majority of lipids in the vegetable oils that are used for deep frying are triglycerides which are comprised of a glycerol molecule esterified to three fatty acids. Fatty acids all have a long carbon chain with a terminal carboxyl group. The fatty acids components of triglycerides can either be saturated,(fully hydrogenated) or they may contain double bonds (unsaturated). The naturally occurring unsaturated fatty acids are also almost all in what is called the cis configuration (hydrogen atoms oriented on the same side of the carbon-carbon double bond). Hydrogenation: Saturated fatty acids have higher melting points than unsaturated fatty acids with a similar size, and thus were considered better for deep frying. But, many years of research indicated that saturated fats cause an increase in LDL cholesterol. This led the food industry to switch to hydrogenated fats that were solid at room temperature, and eliminated of the most unsaturated fatty acids. However, the discovery that the trans fatty acids formed during hydrogenation increased LDL cholesterol and also decreased the “good" HDL cholesterol. These discoveries in recommendations for dietary fats over the past several decades led to consumer confusion over which fats are healthiest. Hydrogenation and trans fatty acids are no longer acceptable. Polyunsaturated fatty acids: Polyunsaturated fatty acids (PUFAs), including the 18-carbon atom linoleic and linolenic acids, contain more than one carbon-carbon double bond, are present in significant quantities in many vegetable oils. They are often referred to as essential fatty acids since they are precursors required for our bodies to produce the 20-carbon atom arachidonic acid. This PUFA is the precursor of prostaglandins that are centrally involved in regulating many processes in our bodies. However, the same PUFAs are more readily oxidized and degraded by the high temperatures involved in deep frying than unsaturated or monounsaturated fatty acids such as oleic acid. In contrast, vegetable oils high in monounsaturated fatty acids - including safflower, sunflower and high oleic soy and Canola oils – are healthier and degrade more slowly. Deep Frying Byproducts: The rate of oxidative degradation of frying oils depends on the oil type, its surface/volume ratio, temperature, heating process, the food and the its immersion and even the characteristics of the frying container. Extended exposure of oil to high temperatures and air can generate highly oxidized, potentially toxic products. Deep frying conditions cause triglycerides to hydrolyze – freeing the fatty acids from the glycerol backbone. The fatty acids, especially the carbon-carbon double bonds of unsaturated fatty acids are then oxidized yielding a large number of aldehydes, ketones, epoxides. Some of these byproducts including trans fatty acids, hydroxylinoleic acid, and acrylamide are well known health hazards. Tracking Fry Oil Degradation: Efforts to monitor frying oil degradation have included a range of approaches, including observing the color of the oil, smoking, foaming and the taste of the food products, etc. Many of these are subjective. For example, the smoke point has several limitations when it comes to choosing the right oil for cooking. Some are highly unstable some cooking oils can have relatively high smoke points but still aren't suitable for high-heat cooking. After decades of research, measurements of Total Polar Compounds (TPC) are now accepted as the most reliable measure of oil quality. Measuring the concentration of TPCs is the best indicator for determining oil degradation. Healthy regulations: Although there is not one specific worldwide regulation for frying oil quality, many countries have guidelines or regulations restricting how much frying oil can be repeatedly used. These rules are based on extensive studies of frying oil stability during cooking and the generation of byproducts with deleterious effects in human health. Even in countries such as the USA and Australia, where TPC is not regulated, it is increasingly being used by foodservice operators as a benchmark for determining when to dispose of frying oil. The specific upper limit for TPC in frying oils used in food service for several countries are listed below.

Publications on the health hazards of used

frying oil

Q. Zhang, A.S.M. Saleh, J. Chen and Q. Shen. Chemical alterations taken place during deep-fat frying based on certain reaction products: A review. Chemistry and Physics of Lipids, 2012, 165, p. 662– 681, 2012. J.B. Riera and R. Codony, Report Title: “Recycled Cooking Oils: Assessment of risks for public health.” Department of Nutrition, University of Barcelona, Spain European Parliament Directorate General for Research Directorate A. The STOA Programme, September 2000. A. Sebastian, S.M. Ghazani and A. G. Marangoni, Quality and safety of frying oils used in restaurants. Food Research International, 64, p. 420–423, 2014. H.H. Hosseini, M. Ghorbani and N. Meshginfar. A Review on Frying: Procedure, Fat, Deterioration Progress and Health Hazards, Journal of the American Oil Chemists’ Society, 93, p. 445–466, 2016. F. Lu, X. Wu, China food safety hits the “gutter”. Food Control, 41, p. 134-138, 2014.