• Recommendations for used Frying Oils and Fats

    11th 11th International Deep-Frying Symposium - Optimum and Sustainable Deep-Frying 27 - 29 March 2023, Hamburg, Germany
    1. The mostimportant quality element in frying is the sensory properties of the fried food.
    -> The fryer operator must strive to produce high quality, safe products of good appearance with desirable flavor, aroma, and textural characteristics.
    -> This is accomplished through a comprehensive oil management program which includes filtration/treatment.
    -> Failure to establish such a program increases the probability that food quality will be compromised and there will be a loss of market share.

    2. The best and most objective indices of frying oil quality is Total Polar Compounds(TPC).
    -> A limit value of 24% TPC cannot always be used as a basis for the use life of the frying medium.
    -> Together with the analytical criterion di-and polymeric TAGs(DPTG) and applying as simple statistic function to calculate the probability of discard it is possible to calculate the further use of the frying oil independent of the type of oil or fried food and temperature.
    -> There is n ocorrelation of TPC and acid value.

    3. The most important element for understanding deep-fat frying is the frying study.
    -> The person conducting the study must establish a baseline (existing conditions) and compare that to a changed system.
    -> These studies entail chemical analyses of fresh and degrading oils, sensory evaluation of foods being fried, oil usage and many other parameters.
    -> The completed study becomes the decision making tool.

    4. Fryer operators must conduct a risk assessment.
    -> All ingredients, raw materials, steps int he process, products being fried and degradation products in the oil should be part of their HACCP/Food Safety Management System (FSMS).
    -> The risk assessment should utilize Severity of Occurrence and Likelihood of Occurrence to establish a risk rating.
    -> High risk items must be addressed in the food safety program as a Critical Control Point (CCP) or Preventive Control.

    5. The name “Free fatty acids” is a misleading expression for the measurement for acidity in used fryin goils.
    -> The formation of hydrolytic products such as MG, DG and free fatty acids during deep-frying is marginal and not relevant.
    -> Only oxidation and polymerization products are relevant for the quality of used frying oils.
    -> Oxidation of unsaturated triacylglycerols leads to the formation of carboxylic acids groups with a glycerol backbone which are also calculated as AV

    6. Passive filtration helps to maintain the quality for a longer use
    -> Removal of particles.
    -> Maybe filtration results in lower amounts of 3-MCPD esters.

    7. Acidity of frying oils has an impact on the formation of acrylamide
    -> For products fried in frying oils with an acidity higher than 0.5mg KOH/kg a significant reduction of acrylamide was observed.
    -> Formation of acrylamide is independent from the type of used frying oil.

    8. Quick tests are very useful for a fast and regular evaluation of frying oils in the process
    -> Regular examination of oil quality helps to improve and maintain product quality.
    -> Calibration of the instrument with standard methods is necessary.
    -> Applicability of the point of discard by quick tests in routine has to be checked.
    -> Digital solutions are available.
    -> Instruments nowadays are able to give more detailed information.

    9. A radical degradation mechanism at lower temperatures in combination with a proton catalyzed reaction at elevated temperatures have to be assumed to explain different routes of oil degradation during deep frying.

    -> Fresh oils hould be checked for the occurrence of contaminants before application for deep frying.
    -> Refined oils are safe with regard to allergens, while cold press or expeller oils may have a risk.
    -> Situation for 3-MCPD and glycidylesters during deep frying is not clear, many questions are still open, not only the oil should be taken into consideration but also all other aspects of the process, such as ingredients (emulsifier) or the heating source.
    -> If mineral oil components are in the frying oil there are some losses during the frying process.
    -> Clorinated paraffins might migrate from different sources into food.

    10th International Symposium on Deep-Fat Frying - Better Food by New Insights into Deep Frying, 08-10.03.2020, Hagen, Germany
    1. Sensory parameters of food is the prime quality index.

    2. The EU should harmonize guidelines/regulations for restaurant and food service frying in Europe.

    3. Frying oil must not exceed 24% total polar material and 12% polymers to ensure food safety. Better food quality may require lower limits depending on the frying system.

    4. More work should be done, using statistical evaluations of analytical parameters including sensory assessments, to characterize frying oil degradation and to determine discard points. The results shall then be tested to verify their quality.

    5. Process technology should constantly be optimised to keep the level of contaminants as low as reasonably achievable.

    7th International Symposium on Deep-Fat Frying - Optimum frying for safe and improved quality fried foods, 20-22 February 2013, San Francisco, CA/USA
    As with past International Symposia on Deep-Fat Frying, the participants generated a series of recommendations for enhancing the science and technology of frying. These recommendations were:

    1. Support risk-based research and analysis of data to more clearly define safety of potentially hazardous oil degradation products, particularly as oxidized products, and/or those formed in foods during frying. We recommend that these evaluations be expanded to examine the whole food system.

    2.Operations working with fried foods at both the restaurant and industrial level need to emphasize what they are doing to produce more healthy meal items (holistic approach).

    3. Continue to encourage the development, quantification and validation of rapid test technologies for monitoring fresh and used oil properties.

    4. Fryer operators must clearly define specifications for their frying oil(s) with their suppliers and initiate programs to ensure that those specifications are being met.

    5. Fryer operators must establish a baseline for their current operations. This serves as a yardstick to properly evaluate any changes to the system, whether that change is a new oil, filter system or product mix. This baseline should include but need not be limited to oil chemistry, food quality, organoleptic parameters of food and operational issues.

    6. The potential microbiological risks inherent with coated products and coating applicators should be researched and the real risk defined.

    7. The group reaffirms their 2000 recommendation that the best indices for assessment of used oils are total polar materials (TPM) and polymeric triglycerides using recognized methods. Peroxide value, free fatty acids, and anisidine value should not be used as regulatory indices when it comes to monitoring and comparing degree of degradation of different frying oils.

    8. Scientists from the European Union working in industry, academia and government should meet to evaluate current regulations for frying oils with regards to harmonization across the EU to ensure the production of safe foods. Regulations should be supported by clinical data.

    6th International Symposium on Deep-Frying - Errors and Myths of Industrial and Catering Frying: 22-24 May 2011 in Hagen, Germany
    The first five International Symposia on Deep-Fay Frying have served as a forum for establishing regulatory guidelines for Europe, provided information on issues such as acrylamide and helped set the stage for reduction of trans-fatty acids in foods and food processing. In addition, the Symposia have served as a meeting place for oil chemists the world over to meet, exchange ideas and get to know one another in a professional yet casual environment.

    The topics for 2011 Symposium in Hagen included issues such as health and wellness (obesity, acrylamide), means for establishing processing parameters, means for oil improving oil quality during deep-fat frying (filtering and oil improving agents), and engineering and physical chemistry aspects such as reducing oil uptake and developments in no- and low trans fatty acid oils.

    As in the past, the attendees gathered together at the end of the meeting to develop a series of recommendations and "next steps" for the future. These recommendations may be seen below.

    Christian Gertz and Rick Stier


    1. It is well-established that the heating of edible oils and fats results in both thermal and oxidative degradation processes, the end products of which may reduce product quality and may be potential health risks. The goal of the fryer operator is to minimize these degradation processes. This may be accomplished by understanding the mechanisms of thermal-oxidative stability and optimizing storage conditions and process parameters to minimize these effects. It is strongly recommended to avoid the use of oils/fats with trans fatty acids and/or high levels of saturated fatty acids (preferably <15%). In kitchens with poor exhaust system the use of oils containing high shares of linolenic acid (eg., rapeseed, soybean oil) should not be used. Linolenic acid decomposes to volatile acroleine at high temperatures (deep-frying temperature) This compound is considered to be a carcinogen. Acroleine in the air will result in irritation of the eyes and mucous membranes of the respiratory tract.

    2. Research also demonstrates that mono-acid-rich oils form oxidized monomeric triglycerides similar to those oils rich in linoleic acid such as sunflower oil. For this reason it is important to minimize the thermal-oxidative degradation of vegetable oils and fats in food production. Studies of the University of Vienna shows that oxidized monomeric triglycerides, as a degradation product of oleic acid, are absorbed in the human stomach and the intestinal tract. These degradation products have been linked to cardiovascular disease and type 2 diabetes. Mono-oxidized products are predominately formed in high oleic oils whereas the dimerisation is the preferred route of degradation in oils rich in polyunsaturates.


    Proper processing and stabilization of vegetable oils are the critical factors for quality during frying. Oxidative is the primary mechanism of degradation between 60 and 130 °C due to the more intense contact of the oil with oxygen. Holding oils between these temperatures should be avoided when oils are not in use for frying. In addition, the melting of solid fats at high temperatures must be avoided.

    During the production process moderate and optimal frying temperatures will minimize the potential for oil degradation. Used frying oils should be filtered by active or passive filtration in order to remove food residues between use in production and foodservice operations.

    When cleaning fryers it is imperative residual cleaning compounds must be removed by rinsing and/or neutralization with acids. "Soap residues" in the fryer will react with the oil and result in increased the thermal-oxidative degradation of the oils.

    Product quality/Deep-frying process

    The first seconds of the frying process are crucial for the development of flavor and textural characteristics of the fried food. These characteristics include crust formation and oil pickup. The structural characteristics (porosity) will directly affect the heat-mass transfer between oil and food. Heat energy is transferred from the oil to the food, while moisture is given from the food to the oil. Excessive temperatures may cause a non-uniform crust with large pores, so that moisture is release is rapd and uncontrolled. If the moisture pressure decreases too fast the temperature increases in the boundary zone can result in an increased rate of acrylamide formation. Moderate temperatures at the beginning of frying encourage the development of a more structured through controlled heat-mass-transfer. Once the crust has formed, frying temperature can be increased continuously during the deep-frying process.

    Studies show that in general only 20% of the total fat is absorbed during the frying process. A much larger percentage (80%) is taken up while the food cools down. In this phase a vacuum is formed in the capillaries of the crust that will draw the oil from the surface into the interior of the food. Industrial frying facilities use so called "defatter"-units to minimize this effect. These units keep the fried goods at high temperature after frying and remove the oil from the surface in a hot air stream.

    To ensure the quality of fried foods, it is also extremely important to minimize the degree of thermal-oxidative degradation of the frying oils. The composition of the fat in fried products has nearly the same composition as the used frying fat. Because of this, the quality of the oil will determine the quality of the fried foods. The oil will affect flavor, aroma, appearance, storage stability and the content of potentially harmful degradation products, like trans fatty acids. Although the regulatory limits in Europe range between 24 - 25% polar compounds, frying oils with polar compound content of more than 19% usually result in the production of foods with poor sensory characteristics.

    Analytics/ Judgment of vegetable oils and fats

    Polar compounds and polymeric triglycerides remain the most reliable chemical indicators for the chemical analysis of used frying oils and fats. The chemical indicators, such as free fatty acids, which are a measure of primary and secondary degradation products, can not be used for a meaningful assessment. These indicators will vary depending upon the type of oil and the conditions under which it is used. Many of these primary and secondary degradation products are steam volatile or are metabolized to other breakdown products. Under controlled conditions or in controlled studies, indicators such as FFA and anisidine value (especially for pastry production) may be used.

    For fresh oils, the acid value (free fatty acid content) is routinely used as a selective indicator for the oxidative degradation status. The FFA-value should be as low as possible. In addition, the smoke point can be a valuable indicator of potential frying performance tool in this case.

    It is not recommended to solely rely on methods like Rancimat to evaluate stability of vegetable oils and fats or to predict the stability for use in deep-frying process, or to evaluate the impact of stabilizing ingredients and additives. This method simulates the behavior of oils/fats in a temperature range that is much lower than real frying conditions and simulates only the oxidation degradation. It cannot simulate polymerisation. In addition, this instrument cannot predict the interaction of the fried food with the oil. To obtain a better picture of oil performance and stability, it is recommended that the oil be heated under controlled conditions at 170 °C for 16 hours in a glass tube. Degradation products, such as polymers or polar studies to make a kitchen test with the food to be fried. Industrial food producers should understand the thermoxidative changes in their frying oils, especially below 15% polar compounds. The formation of undesirable oxidation products has to be avoided as the end result will be off-flavors and a shorter shelf life, even in frozen foods. The use of near infrared instrumentation is recommended as this system rapidly measures the polar content, polymerized triglycerides, besides free fatty acids, and anisidine value or C16/C18:2 ratios with a high confidence.

    In fast food restaurants where the products are prepared for the direct consummation the limits of degradation are much higher (i.e. 24% polar materials) and may be monitored by units that measure and related dielectric constant to the degree of degradation. Results are expressed using a value that corresponds to the amount of polar material present in the frying oil. Care must be taken when using these instruments to validate them against the official method.

    Even though rapid test technology has evolved, the sensory evaluation of vegetable oils and fried foods remains the most important tool for quality control and assurance. In addition, oil color and free fatty acid content are not an appropriate indicator for food or oil quality. The main target and demand of all scientific experts is the cross-border harmonization of methods, criteria and limits.

    Food security/Allergens

    One of the major topics within the context of food safety is "allergens" and allergen control. The eight major allergens in food considered by the experts are: tree nuts,peanut/groundnut, soy, egg, milk, fish, wheat and crustacean shellfish. These eight allergens make up 90% of known food allergens with people. However, over 160 foods have been identified as being allergenic.

    Fryer operators whether at the industrial or restaurant level must address allergenic substances/foods when conducting a hazard analysis as part of the their food safety management system. The common practice of multi-pot-frying, that is frying different foods in a single fryer, may pose significant risks to the consumer. There is anecdotal information that has linked fish-contaminated restaurant French fries with a fatal allergenic reaction. Additional research in this field is needed.

    Questions to be answered are: *What is the behavior of allergens during deep-frying. Are they oil soluble and are they transferred between different foods. *Can allergens be filtered from the oil? *Are there effective technical possibilities to avoid cross contamination in case of multi-pot-frying?
    Unless these questions can be answered it is recommended to abstain from multi-pot practice. This is not only valid for gastronomy but also for industrial scale food producers. The above presented recommendations and findings are a summary of the presentations of the "6th International Symposium on deep-frying in Hagen 2011" was presented by the following international experts: Dagmar Behmer, Veronika Somoza, Bernd Brinkmann, Christian Gertz, Monoij Gupta, Bertrand Matthäus, Ricard Stier, and Rüdiger Weisshaar,

    4th International Symposium on Deep-Fat Frying: 11-13 January 2004, Hagen/Westphalia, Germany
    During this symposium, delegates discussed and adopted new recommendations on frying oils to complement recommendations adopted during the 3rd symposium (see below).

    1) A risk analysis should be conducted on heated fats and oils and especially the foods being fried in those oils. This analysis should be conducted by a multidisciplinary team. Risk assessment is an essential first step to determine whether regulations should be implemented to protect the public health.

    2) It is strongly recommended that industrial and foodservice fryers take steps to optimize processing parameters, such as reducing the temperature of frying oils, to optimize quality and safety in fried foods and the work environment.

    3) We encourage the continued research into developing alternatives to existing frying fats and oils containing trans fatty acids that will not only be more healthy but will provide the functionality needed to produce the foods demanded by the consumer.

    4) We recommend that all industrial, foodservice fryers adopt the principles of HACCP and/or Guides for Good Hygienic Practices to ensure consumer safety according to EU recommendations or the Codex Alimentarius Principles of Food Hygiene.

    5) Food processors and restaurant operators should make an effort to develop a direct relationship between food quality and the two best indices of frying oil quality; total polar materials and total polymers. If this is not possible, the operation should make every effort to establish a relationship between food quality and a measurable physical or chemical index.

    6) The DGF should prepare and publish a reference guide to test methods used to evaluate frying oils. This document should describe all methods applied for both fresh and used frying oils, and emphasize how those methods should be used to evaluate oil quality and safety and its relationship to food quality. This guide should be reviewed and updated on a regular basis.

    7) We encourage continued research targeted at obtaining a better understanding of the formation of potentially harmful compounds, such as acrylamide and oxidized compounds. These research efforts may include the development of new or improved frying processes, process interventions, and new products or systems that will result in the production of foods with lower levels of such compounds.

    8) The food industry, professional societies and the academic community should make an effort to educate consumers, retailers and caterers on proper cooking methods and food handling.

    3rd International Symposium on Deep-Fat Frying: March 20-21, 2000, Hagen/Westphalia, Germany
    On this symposium, eight Recommendations for Frying Oils were discussed and adopted by the delegates:

    1) Principle quality index for deep-fat frying should be sensory parameters of the food being fried

    2) Analysis of suspect frying fats and oils should utilize two tests to confirm abuse. Recommended analyses should be:

    Total Polar Materials (24%)
    Polymeric Materials (12%)

    3) The use of rapid tests for monitoring oil quality are recommended. Rapid tests should exhibit the following characteristics:

    *Correlate with internationally recognized standard methods *Provide an objective index *Be easy to use *Safe for use in food processing/preparation area *Quantify with oil degradation *Field rugged

    4) Affirming previous work: There are no health concerns associated with consumption of frying fats and oils that have not been abused at normal frying conditions.

    5) Encourage development of new and improved methods that provide fats and oils chemists and the food industry with tools to conduct work more quickly and easily. Work should strive to develop methods that are environmentally friendly, using lower quantities of and less hazardous solvent systems.

    6) Encourage and support basic research focused on understanding the dynamics of deep-fat frying and the frying process. Research should be cross-discipline encompassing oil chemistry, food engineering, sensory science, food chemistry and nutritional sciences.

    7) One of the basic tools to assure food and oil quality is the use of filtration. Filter materials should be used to maintain oil quality as needed.

    8) Used, but not abused, frying oils may be topped up or diluted with fresh oil with no adverse effects on quality. Abused fats and oils were defined in the first two recommendations developed during this program.


    Define what constitutes a long life frying oil claim in keeping with recommendations 1 and 2.