11
Safety Assessment of Food Frying

11.1 Introduction

Frying fats and oils have been subject to much attention over their health risks. In the early 1970s, the German authorities received several complaints about the quality of fried food served in restaurants, which led to a detailed inspection of the food service industry. This investigation revealed that the quality of the frying medium has a direct impact on the quality of the final fried product. Thus, the German Society for Fat Science (DGF) recommended several regulations for the use of frying oils in restaurants. Later studies revealed several quality parameters that can be used to assess the quality of an oil or fat. These include peroxide value, free fatty acid (FFA) content, anisidine value, iodine value, carbonyl value, colour, and refractive index.

Stier (2001) reviewed some of the important criteria used to assess the quality of frying fats. These are based on the objectives of producing fried foods of high quality and controlling the degradation of oils during frying to achieve maximum economic parameters. The basic criteria were originally obtained from the work of Robertson (1968).

  • Proper design, construction, and maintenance of equipment.
  • Proper operation of equipment.
  • Proper cleaning of equipment.
  • Monitoring of chemical indices of oil degradation.
  • Minimization of exposure to ultraviolet (UV) light.
  • Keeping salt and other sources of metal away from oil.
  • Filtering oil regularly.

Once the frying process is initiated, it begins to degrade the frying medium, in a process that cannot be reversed. However, recent research revealed that this degradation can be slowed by various physical processes, in order to achieve maximum use from frying oils.

11.2 Guideline for Assessment

The most important issue in the evaluation of deep‐frying oil quality is finding the optimal point at which to discard the used oil (Weisshaar 2014). Recommendations from the 3rd International Symposium on Deep‐Fat Frying in 2000 define some criteria for the assessment of used frying oils and frying fats (Donner and Ritcher 2000):

  • The principle quality index for deep fat frying should be the sensory parameters of the food being fried.
  • Analysis of suspect frying fats and oils should utilize two tests to confirm abuse:
    • – Total polar materials (<24%).
    • – Polymeric triglycerides (<12%).

When oxidative alterations strongly predominate over thermal alterations, serious sensory defects can present before total polar materials (TPM) and polymer triglycerides (PTG) reach the recommended limits. In that case, additional parameters like anisidine value or carbonyl value should be used for evaluation.

In many countries, regulations for abused frying fats and oils were established as guidelines or regulatory limits, addressed to fryer operators and official food control agencies. In most cases, TPM is the critical parameter, with limits from 24 to 27%. A synoptic table of the actual regulations used in different countries was recently presented by Stier (2013). The author stated that regulations are largely in line with those just given, but further harmonization is desirable, at least within the European Union.

For the daily practice of frying, it is reasonable to use rapid tests and to define individual cut‐off criteria based on correlation to sensory attributes and the practical experience of the fryer operator. From time to time, individual cut‐off values should be rechecked by laboratory analysis.

The European Federation for the Science and Technology of Lipids (Euro Fed Lipid) and the American Oil Chemist's Society (AOCS) hosted the 7th International Symposium on Deep‐Fat Frying from February 20 to 22, 2013 in San Francisco, CA. The program was held at the Radisson Fisherman's Wharf and featured 20 speakers. It was attended by more than 80 scientists from all over the world (Gertz and Stier 2013). The aim was to help processors, food service operators, regulators, suppliers, and academics to better understand the frying process in the light of a worldwide emphasis on health and wellness, and concerns about the effect of fried products on obesity. Rather than condemning the frying process, the aim was to improve its efficiency, understand the performance of the new generation of healthy oils (low‐ and no‐trans), and look to the past for lessons on how to do things better.

Food processors, restaurant operators, and suppliers to these industries, which include oil producers, food and ingredient suppliers, equipment manufacturers, and the service trade, have to understand that they must produce foods that are not only safe and nutritious but also tasty and healthy. The pressure on the industry is great, but an understanding of the processes and technologies, the markets and demands can help build a basis on which to grow. Like at past International Symposia on Deep‐Fat Frying, the participants generated a series of recommendations for enhancing the science and technology of frying, as follows:

  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 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 triacylglycerols using recognized methods. Peroxide value (PV), free fatty acids, and anisidine value should not be used as regulatory indices when it comes to monitoring and comparing the degree of degradation of different frying oils.
  8. Scientists from the European Union working in the industry, academia, and the 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 (Gertz and Stier 2013).

11.3 Quality Indicators for Used Frying Oils

A number of analytical laboratory methods for monitoring frying oil quality have been reported in the last 4 decades. At DGF's 1st Symposium for Used Frying Oils and Fats in 1973, smoke point and petroleum‐ether insoluble oxidized fatty acids (OXF) were recommended as suitable parameters for the evaluation of frying fat quality. The determination of petroleum‐ether insoluble OXF is extremely laborious and time‐consuming, and requires large amounts of organic solvents, so this method found no substantial proliferation. In the following years, TPM and PTG were found to be the most reliable methods for monitoring the changes in fats and oils during the frying process. A number of official methods (e.g. from AOCS and DGF) were published for the determination of TPM and PTG (DGF 2010; Firestone 2013). Determination of TPM in frying oil is usually performed by silica gel column chromatography and gravimetric analysis (Guhr et al. 1981). As an alternative to time‐ and solvent‐consuming classical column chromatography, rapid methods using microcolumns or high‐performance liquid chromatographic (HPLC) methods have been reported for the analysis of TPM (Kaufmann et al. 2001; Caldwell et al. 2011). For analysis of PTG, high‐performance liquid chromatography size‐exclusion chromatography (HPLC‐SEC) is used. Separation can be achieved with polymer‐based separation phases that can be used with organic solvents. Detection can be achieved with a refractive index detector (RID) or evaporative light scattering detector (ELSD). Several studies have shown that there is a strong correlation between TPM and PTG in used frying oils (Gertz 2000; Farhoosh and Tavassoli‐Kafrani 2011). It can be stated that both parameters – TPM and PTG – are the best indicators to check the quality of used frying oils. Some important quality parameters are given in Table 11.1.

Table 11.1 Quality parameters for evaluation of the characteristics of frying fats and oils.

S. NoParameterMethod(s) appliedPurpose
 1Peroxide value (PV)Spectroscopic and titrimetricDetermine the hydroperoxides formed
 2Free fatty acid (FFA)TitrimetricHelp determine stability
 3Iodine value (IV)TitrimetricDetermine the amount of unsaturation present in fatty acids
 4Anisidine value (AV)SpectroscopicDetermine the secondary oxidation
 5Saponification number (SN)TitrimetricDetermine the soap formation ability of frying fats
 6Fatty acids profileChromatographicObtain an exact profile of each fatty acid content
 7Total polar materials (TPM)Chromatographic and quick testEvaluate the level of polar materials after frying
 8Glyceride contents (GC)ChromatographicDetermine mono‐, di‐, and triacylglycerol compositions
 9Total polymeric materialsChromatographic & quick testDetermine the level of polymerization of triglycerides during frying
10Metals content (MC)SpectrometricDetermine the degree of metal contamination during preparation of the frying medium
11Total phenolic contents (TPC)SpectroscopicSpecific for plant oils – evaluate TPC

But there is a little fly in the ointment: when oxidative alterations strongly predominate over thermal alterations, sensory defects like train oil or fishy flavour can appear long before TPM and PTG reach critical values. This can be observed for frying oils with higher amounts of linolenic acid (>3%) or for oils in open fryers with an unfavourable surface‐to‐volume (S/V) ratio, used for the preparation of doughnuts and other yeast‐raised baked goods. In these cases, anisidine value (Tompkins and Perkins 1999; Aladedunye and Przybylski 2009), carbonyl value (Farhoosh and Tavassoli‐Kafrani 2011; Endo et al. 2003; Farhoosh and Moosavi 2008), or conjugated diene value at 234 nm (Farhoosh et al. 2008) can be helpful tools in evaluating oxygen‐stressed frying oils, considering the oil's type.

A huge number of volatile compounds are formed during the frying process, according to the nature of the oil and the conditions of frying. These volatiles cover different classes of compound, such as alkanes, alkenes, alcohols, saturated and unsaturated aldehydes and ketones, and short‐chain fatty acids. They are responsible for the typical odour of both good and abused frying oil, and can be used as marker compounds for frying oil quality. Some of them, like acrolein and other α,β‐unsaturated aldehydes, are undesirable because of health concerns. For analysis, sophisticated techniques like headspace gas chromatography mass spectrometry (GC‐MS) are used (Guillén and Goicoechea 2008; Berdeaux et al. 2012; Petersen et al. 2013).

A novel approach to the evaluation of oxidative altered frying oils might be the detection of triglyceride‐bound epoxy fatty acids by gas chromatography with flame ionization detection (GC‐FID) (Velasco et al. 2004; Mubiru et al. 2013). Epoxy fatty acids are present in the g/kg range in used frying oils. They are unexpectedly stable end products of oxidation, and like TPM and PTG, they are accumulated during the frying process.

In the laboratory of Dr. Rüdiger Weisshaar, the development of a new ‘hydrogen bromide value’ (HBV), which correlates to the content of epoxy fatty acids, is under way. In this work, the reaction of HBr with epoxy groups is used to develop a simple analytical method of estimating the content of epoxy acids in used frying oils. The first results look very promising (Weisshaar 2014).

FFAs are very easy to determine by titration and have been frequently applied as a quality parameter for used frying oils (Fritsch 1981; Stevenson et al. 1984). The amount of FFAs covers both FFAs formed by hydrolysis and short‐chain fatty acids formed by oxidation. Short‐chain fatty acids are volatile and are stripped off from the hot frying oil, so their amount will depend on many accidental individual circumstances. For example, the level of FFAs increases strongly if dimethylpolysiloxane is used as an antifoaming additive, due to surface effects which hinder volatile fatty acids from evaporating. Many researchers have come to the conclusion that there is no direct relationship between FFA content and the quality of a used frying oil, and FFAs are no longer considered a reliable marker for frying fat deterioration (Gertz 2000).

11.4 Physical Assessment

11.4.1 Sensory Evaluation, Colour, and Foaming

The organoleptic examination is the first and most important step in the evaluation of frying fat quality. If the taste and flavour of a frying oil or fat are not acceptable, neither will be any products fried in it. Smell and taste are subjective qualities, but in many cases (e.g. restaurants and small fast food outlets) they will be the only form of quality control applied to an oil or fat used in frying. The results of a sensory analysis can be significantly enhanced if it is performed under scientific conditions by a trained sensory panel (Ravelli et al. 2010).

There are numerous studies aimed at assisting or replacing the human ability to smell through the use of a so‐called ‘electronic nose’ (Mildner‐Szkudlarz et al. 2008). This is usually an array of multiple metal‐oxide sensors that are sensitive to different volatile compounds formed by oxidative alteration of oils. Although tested successfully for some special applications, electronic noses have not yet found broad distribution because of their high cost and unsuitability for field use.

Changes in colour are the most eye‐catching alterations of frying fats during their time of use. There is no correlation between colour and frying fat quality – good oil can be a dark and bad oil can be light in colour (Stier 2004). However, the grade of dark colouring can be helpful if a consistent constellation of frying oil and fried goods is present. If a defined grade of dark colour is reached, the oil is considered to be unfit for use and should be discarded. For this purpose, schemes for colour comparison are provided by different manufacturers.

Altered frying oils begin to foam because of the formation of volatiles like short‐chain fatty acids and of different surface‐active substances. There is no real correlation between foam height and food quality, but if foaming is too strong, the oil can boil over.

11.4.2 Quick Tests for Viscosity and Dielectricity

Polymer compounds formed during the use of a frying oil lead to an increase in that oil's viscosity. Therefore, viscosity is an excellent tool for monitoring frying fat quality. There is a strange correlation between viscosity, TPM, and PTG (Gertz 2000). Unfortunately, the two instruments designed to measure this, developed by Leatherhead/GEC Marconi (Kress‐Rogers et al. 1990) and Gertz (Fri‐Check®), are no longer manufactured (Gertz 2000).

During the frying process, the level of polar material increases continuously. With increasing TPM, the dielectric constant of the frying oil increases too. The dielectric constant can be easily measured electronically. The first instrument designed for this purpose was the food oil sensor (FOS) from Northern Instrument Corporation (Lino Lakes, MN, USA). Using this instrument, Hein et al. (1998) conducted basic studies of the correlation between dielectric properties and TPM. They found a very good correlation in the range of 0.8–0.95, as determined by column chromatography and the FOS.

The FOS is again no longer manufactured, but some other devices based on measuring the dielectric constant of frying oil are on the market, such as the CapSens 5000 (Centre for Chemical Information Technology, Switzerland), FOM 310 (Ebro Electronics, Germany), and Testo 265 (Testo AG, Germany). The CapSens instrument is a new version of the FOS; a small sample of frying oil is put into the heated detector and the result is displayed either as an FOS value or as % TPM. FOM 310 and Testo 265 also provide results as % TPM, but in these cases, the sensor probe is immersed directly into the hot oil bath of the fryer. Good accordance with TPM, as determined by column chromatography, was reported for these instruments (Bansal et al. 2010a).

In practice, there are some concerns around the use of instruments that measure the dielectricity constant (Gertz 2000). Traces of water, salt, and minerals may enhance polarity and adversely affect their measurements. Filtration of test samples may be necessary to obtain more reliable results. The disturbing effect of water can be compensated when the oil is measured above 110 °C. Test results are also strongly influenced by the nature and fatty acid composition of the frying oil. Short‐ and medium‐chain fatty acids are more polar than long‐chain fatty acids. Therefore, for short‐ and medium‐chain fats like milk fat and coconut oil, significantly higher TPM results will be obtained.

An alternative to electronic tests is a quick test for polar materials, based on chemical test principles. The most important are the 3M PCT 120 oil tester (3M Inc., USA) and the TPM Veri‐Fry (Test Kit Technologies Inc., USA) (Xu 1999).

11.5 Chemical Assessment

11.5.1 Chemical Quick Tests

There are several test kits available for the detection of various chemical parameters like FFA and oxidation products using colour reactions, pH indicators, or redox indicators. Several studies of the performance of different test kits and the correlation of their results to other analytical data have been reported in recent decades (Gertz 2000; Muhl et al. 2000; Innawong et al. 2004b; Sanibal and Mancini‐Filho 2004; Stier 2004; Marmesat et al. 2007; Bansal et al. 2010a, 2010b; Chen et al. 2013; Gertz and Stier 2013; Osawa et al. 2013; Gertz and Behmer 2014). Kalogianni et al. (2017) recently reviewed and evaluated several quick tests for the evaluation of different quality characteristics, the details of which are given in Table 11.2.

Table 11.2 Overview of original and previous independent research on rapid methods of determining frying oil quality.

Source: Reproduced with kind permission of John Wiley & Sons (Kalogianni et al. 2017).

TestManufacturerIn the marketUsable in small establishmentsPrincipleResearch studiesOil typeFood typeCorrelation/comparison of results
AV‐checkAdaptec (Japan)YesYesMeasurement of acid value – colour comparison————
Electronic noseCyrano Sciences and Alpha (USA and France)YesNoArray of metal‐oxide sensors, sensitive to volatile compoundsMuhl et al. (2000), Innawong et al. (2004b)Soybean peanut oilFrench fries, fish fingers, poultry sticksFFA, dielectric constant
FASafe
AldeSafe
PeroxySafe 		MP Biomedicals (USA)YesNoMeasurement of spectrophotometric absorbance; conversion of the absorbance units to FFABansal et al. (2010a, 2010b), Foo et al. (2006)Refined palm olein; blend of palm olein, sesame oil, and peanut oil; sunflower oil; and partially hydrogenated soybean oilFrozen French fries, frozen chicken nuggetsTPC, FFA, MDA, PV
FOM 320EBRO (Germany)YesYesDielectric constant – correlation with TPCBanasal et al. (2010a, 2010b)Refined palm olein; blend of palm olein, sesame oil, and peanut oil; sunflower oilFrozen French fries, frozen chicken nuggetsTPC, FFA
Food oil sensor/Capsens 5000Northern Instruments (USA)/C‐CIT Sensors AG (Switzerland)No/YesYesDielectric constant – correlation with TPCBansal et al. (2010a, 2010b), Marmesat et al. (2007)Used frying oils from different origins and establishments; refined palm olein; blend of palm olein, sesame oil, and peanut oil; and sunflower oilFrozen French fries, frozen chicken nuggetsTPC, composition in major fatty acids, PTG, FFA
Fri‐checkFri‐check (Belgium)No—Time for a piston‐like body dropped in a tube containing the oil – related to viscosity and densityOsawa et al. (2013), Chen et al. (2013)Disposal samples from commercial establishmentsUnknownTPC
FritestMerck (Germany)YesYesMeasure of carbonyl compounds – colour comparisonBanasal et al. (2010a, 2010b), Marmesat et al. (2007)Used frying oils from different (unknown) origins and establishments; refined palm olein; blend of palm olein, sesame oil, and peanut oil; and sunflower oilFrozen French fries, frozen chicken nuggetsTPC, composition in major fatty acids, PTG, FFA
Low‐range shortening monitor3M (USA)YesYesRange of FFA – colour comparisonBansal et al. (2010a, 2010b), Kalogianni et al. (2017)Refined palm olein; blend of palm olein, sesame oil, and peanut oil; and sunflower oilFrozen French fries, frozen chicken nuggetsTPC, FFA
Near‐infraredDifferent manufacturersYesNoDetermination of parameters like TPC, PTG, FFA, peroxides, anisidine value, carbonyl value, and conjugated dienoic acidsGertz et al. (2013)UnknownUnknownTPC, PTG, acid value, para‐anisidine value
OptifryMir‐oil (USA)YesYesDielectric constant – correlation with TPC————
OxifritMerck (Germany)YesYesMeasurement of oxidized fatty acids – colour comparisonBanasal et al. (2010a, 2010b), Marmesat et al. (2007)Used frying oils from different (unknown) origins and establishments; refined palm olein; blend of palm olein, sesame oil, and peanut oil; and sunflower oil Unknown
Frozen French fries, frozen chicken nuggets 		TPC, composition in major fatty acids, PTG, FFA
PCT 1203M (France)YesYesCorrelation of dye travel distance with polar compoundsKalogianni et al. (2017)———
Testo 265 Testo 270Testo (Germany)YesYesDielectric constant – correlation with TPCBansal et al. (2010a, 2010b)Refined palm olein; blend of palm olein, sesame oil, and peanut oil; and sunflower oilFrozen French fries, frozen chicken nuggetsTPC, FFA
TPM, FFA, VerifyTest Kit Technologies (USA)YesYesReaction of gel with polar compounds to give a specific colourBansal et al. (2010a, 2010b)Refined palm olein; blend of palm olein, sesame oil, and peanut oil; and sunflower oilFrozen French fries, frozen chicken nuggetsTPC
ViscofritViscofrit (Spain)YesYesMeasurement of the time required to empty a standard funnelOsawa et al. (2013), Marmesat et al. (2007), Kalogianni et al. (2017)Used frying oils from different (unknown) origins and establishmentsUnknownTPC, FFA, PTG

TPC, total polar compounds; PTG, polymerized triacyl glycerols; FFA, free fatty acids.

The test strips of the 3M Shortening Monitor (3M, Inc., USA) are used to determine FFA in the range of 0.0–2.5% (lower range) and 0–7% (higher range) (Kalogianni et al. 2017). As already mentioned, there is only a very poor correlation between the FFA level and the frying fat quality measured as by TPM or PTG.

Oxifrit‐Test, formerly called Rau‐test, can detect OXF using a redox indicator; Fritest can detect carbonyl compounds measuring alkaline colour by comparing with a colour scale. With these tests, frying oils can be classified into four categories from ‘good’ to ‘bad’. Both tests require hazardous and flammable chemicals, so they are unsuitable for use in food production rooms. Another problem is interferences between the basic colour of the frying oil itself and the colour of the reaction. Both tests correlate very poorly with TPM and PTG – they only can detect oxidative deterioration (Marmesat et al. 2007; Bansal et al. 2010b; Weisshaar 2014).

A number of analytical test kits are manufactured under the brand name ‘Safe’. These tests are not typical quick tests but fast and portable laboratory tests. Liquid reagents and solvents and a portable spectrophotometer are required. Results can be achieved much faster than with official laboratory methods. For analysis of frying oils, four test kits have been validated (Yee Foo et al. 2006; Bansal et al. 2010b): PeroxySafe for lipid peroxides, AldeSafe for malondialdehyde, FASafe for FFA, and AlkalSafe for alkenals.

11.5.2 Near‐Infrared Spectroscopy

Near‐infrared spectroscopy (NIRS) is a powerful tool for monitoring the quality of used frying oil. It is a clean, fast, and nondestructive technique that allows the rapid determination of various chemical parameters, such as TPM, PTG, FFA, peroxides, anisidine value, carbonyl value, conjugated dienoic acids (CDA), and trans fatty acids (TFAs) (Boor and Speek 1994; Innawong et al. 2004a; Ng et al. 2007, 2011). In most cases, cuvettes are used, but measurement directly in the oil bath is possible with fibre‐optic probes. Fourier transformation (FT) of the spectra allows for multiple methods of data analysis. In many cases, calibration data can be transferred from one instrument to another of the same type. The great advantage of NIRS compared to other rapid methods is the fact that typical parameters for thermal alteration (PTG and TPM), typical parameters for oxidative alteration (anisidine value, carbonyl value, CDA), and acid values can be detected simultaneously. Thus, a complete picture of different alterations can be achieved rapidly with a single measurement. Recently, the first DGF standard method was developed using NIRS was published (Gertz et al. 2013). A recent study showed that a portable NIRS device can be used to test the acid values of peanuts oils (Yang et al. 2017). Thus, it is not difficult to forecast that NIRS methods will gain strong prominence in the frying industries in coming years.

11.5.3 Mass Spectrometry

Mass spectrometry is one of the most widely accepted techniques for identifying individual components of frying foods and media. Cao et al. (2017) reviewed its use in the quality and safety assessment of cooking oils, highlighting its increasing application in authentication, ageing, and marker detection in used oil.

11.6 Evaluation of Fried Foods

Fried foods are also evaluated for both physical and chemical characteristics. The sensory evaluation of fried foods has received the most attention in recent times. Human sensory panels are usually utilized for this purpose. Colour, taste, crispness, hardness, and other parameters are widely assessed.

Among chemical measures, oil content, water content, and thiobarbituric acid reactive substances (TBARS) have received the greatest attention. Recently, a spectroscopic method was developed to assess TBARS contents in the fast food industry (Zeb and Ullah 2016). This method examines the reaction of malondialdehyde (MDA) and TBA in the glacial acetic acid medium. It was used to determine the TBARS contents in fried fast foods such as Shami kebab, samosa, fried bread, and potato chips. Shami kebab, samosa, and potato chips all had a higher amount of TBARS in a glacial acetic acid–water extraction system than their corresponding pure glacial acetic acid; the reverse was true for fried bread. This method can successfully be used for the determination of TBARS in other food matrices, making it applicable for quality control in the food industry. Several chromatographic methods have been reported to determine different quality indices or toxicants in fried foods.

11.7 The Future of Fried Food Safety

Several countries in the European Union, the Americas, Australasia, and Asia have strict regulations regarding fried food safety. However, a large amount of data is still needed to comprehend the full safety spectrum. Much of the world population may or may not be aware of fried food safety issues, are thus could potentially be exposed to fried food toxicants. Therefore, several steps should be taken to implement and extend already established guidelines to all countries:

  • EU and US regulations should be extended to all member countries of the World Health Organization (WHO). This forum could successfully be used to tackle all health concerns in nonregulated countries.
  • Extensive work is required to analyze the chemistry of different fried foods across a number countries for which data are not available.
  • Risk‐assessment programs should be organized by country on an annual basis, focusing on all types of physical and chemical assessment.
  • Mass spectrometry‐based analysis of quality assessment is an excellent choice for future research on fried food safety.
  • Hazard and risk‐based approaches should be used to ensure fried food safety.

11.8 Key Concepts

  • It is important to follow basic safety criteria when frying.
  • Used frying oils or fats must contain <24% TPM and <12% polymeric triglycerides as standard basic indicators.
  • Other guidelines must be followed to ensure safe food production.
  • Several quality indicators can be analyzed to determine the quality of frying media.
  • Physical measures such as sensory quality, colour, foaming, viscosity, and dielectricity should be evaluated.
  • Several chemical tests, including instrumental quick tests and laboratory analytical methods, must accompany the physical assessment.
  • Existing guidelines and regulations should be extended to nonregulated countries via the WHO.
  • Safe fried foods may contribute to the future health of the next generation.

References

  1. Aladedunye, F.A. and Przybylski, R. (2009). Degradation and nutritional quality changes of oil during frying. Journal of the American Oil Chemists' Society 86: 149–156.
  2. Bansal, G., Zhou, W., Barlow, P.J. et al. (2010a). Evaluation of commercially available rapid test kits for the determination of oil quality in deep‐frying operations. Food Chemistry 121: 621–626.
  3. Bansal, G., Zhou, W., Barlow, P.J. et al. (2010b). Review of rapid tests available for measuring the quality changes in frying oils and comparison with standard methods. Critical Reviews in Food Science and Nutrition 50: 503–514.
  4. Berdeaux, O., Fontagné, S., Sémon, E. et al. (2012). A detailed identification study on high‐temperature degradation products of oleic and linoleic acid methyl esters by GC–MS and GC–FTIR. Chemistry and Physics of Lipids 165: 338–347.
  5. Boor, A. and Speek, A.J. (1994). Determination of the sum of dimer and polymer triglycerides and of acid value of used frying fats and oils by near infrared reflectance spectroscopy. Journal of AOAC International (USA) 77: 1184–1198.
  6. Caldwell, J.D., Cooke, B.S., and Greer, M.K. (2011). High performance liquid chromatography–size exclusion chromatography for rapid analysis of Total polar compounds in used frying oils. Journal of the American Oil Chemists' Society 88: 1669–1674.
  7. Cao, G., Ruan, D., Chen, Z. et al. (2017). Recent developments and applications of mass spectrometry for the quality and safety assessment of cooking oil. Trends in Analytical Chemistry 96: 201–211.
  8. Chen, W.‐A., Chiu, C.P., Cheng, W.‐C. et al. (2013). Total polar compounds and acid values of repeatedly used frying oils measured by standard and rapid methods. Journal of Food and Drug Analysis 21: 58–65.
  9. DGF. 2010. Polymerized triacylglycerols – determination in severely heat stressed fats and oils (deep‐frying fats) by high‐performance size‐exclusion chromatography (HPSEC). DGF Standard Methods. German Society for Fat Science.
  10. Donner, M.G. and Ritcher, W.O. (2000). 3rd international symposium on deep‐fat frying – optimal operation. European Journal of Lipid Science and Technology 102: 306–308.
  11. Endo, Y., Tominaga, M., Tagiri‐Endo, M. et al. (2003). A modified method to estimate total carbonyl compounds in frying oils using 1‐butanol as a solvent. Journal of Oleo Science 52: 353–358.
  12. Farhoosh, R. and Moosavi, S.M. (2008). Carbonyl value in monitoring of the quality of used frying oils. Analytica Chimica Acta 617: 18–21.
  13. Farhoosh, R. and Tavassoli‐Kafrani, M.H. (2011). Simultaneous monitoring of the conventional qualitative indicators during frying of sunflower oil. Food Chemistry 125: 209–213.
  14. Farhoosh, R., Tavakoli, J., and Khodaparast, M.H.H. (2008). Chemical composition and oxidative stability of kernel oils from two current subspecies of Pistacia atlantica in Iran. Journal of the American Oil Chemists' Society 85: 723–729.
  15. Firestone, D. (2013). Determination of polar compounds in frying fats, AOCS Official Method Cd 20‐91. In: Official Methods and Recommended Practices of the AOCS, 6e (ed. D. Firestone). Urbana, IL: American Oil Chemists' Society.
  16. Fritsch, C.W. (1981). Measurements of frying fat deterioration: a brief review. Journal of the American Oil Chemists' Society 58: 272–274.
  17. Gertz, C. (2000). Chemical and physical parameters as quality indicators of used frying fats. European Journal of Lipid Science and Technology 102: 566–572.
  18. Gertz, C. and Stier, R.F. (2013). 7th International Symposium on Deep‐Fat Frying, San Francisco, CA (USA): recommendations to enhance frying. European Journal of Lipid Science and Technology 115: 589–590.
  19. Gertz, C. and Behmer, D. (2014). Application of FT‐NIR spectroscopy in assessment of used frying fats and oils. European Journal of Lipid Science and Technology 116: 756–762.
  20. Gertz, C., Fiebig, H.‐J., and Hancock, J.N.S. (2013). FT‐near infrared (NIR) spectroscopy – screening analysis of used frying fats and oils for rapid determination of polar compounds, polymerized triacylglycerols, acid value and anisidine value [DGF C‐VI 21a (13)]. European Journal of Lipid Science and Technology 115: 1193–1197.
  21. Guhr, C.G.G., Waibel, J., and Arens, M. (1981). Bestimmung der polaren Anteile in Fritierfetten. Fette, Seifen, Anstrichmittel 83: 373–376.
  22. Guillén, M.D. and Goicoechea, E. (2008). Toxic oxygenated α,β‐unsaturated aldehydes and their study in foods: a review. Critical Reviews in Food Science and Nutrition 48: 119–136.
  23. Hein, M., Henning, H., and Isengard, H.D. (1998). Determination of total polar parts with new methods for the quality survey of frying fats and oils. Talanta 47: 447–454.
  24. Innawong, B., Mallikarjunan, P., Irudayaraj, J., and Marcy, J.E. (2004a). The determination of frying oil quality using Fourier transform infrared attenuated total reflectance. LWT – Food Science and Technology 37: 23–28.
  25. Innawong, B., Mallikarjunan, P., and Marcy, J.E. (2004b). The determination of frying oil quality using a chemosensory system. LWT – Food Science and Technology 37: 35–41.
  26. Kalogianni, E.P., Georgiou, D., Romaidi, M. et al. (2017). Rapid methods for frying oil quality determination: evaluation with respect to legislation criteria. Journal of the American Oil Chemists' Society 94: 19–36.
  27. Kaufmann, A., Ryser, B., and Suter, B. (2001). HPLC with evaporative light scattering detection for the determination of polar compounds in used frying oils. European Food Research and Technology 213: 372–376.
  28. Kress‐Rogers, E., Gillatt, P.N., and Rossell, J.B. (1990). Development and evaluation of a novel sensor for the in situ assessment of frying oil quality. Food Control 1: 163–178.
  29. Marmesat, S., Rodrigues, E., Velasco, J., and Dobarganes, C. (2007). Quality of used frying fats and oils: comparison of rapid tests based on chemical and physical oil properties. International Journal of Food Science and Technology 42: 601–608.
  30. Mildner‐Szkudlarz, S., Jeleń, H.H., and Zawirska‐Wojtasiak, R. (2008). The use of electronic and human nose for monitoring rapeseed oil autoxidation. European Journal of Lipid Science and Technology 110: 61–72.
  31. Mubiru, E., Shrestha, K., Papastergiadis, A., and de Meulenaer, B. (2013). Improved gas chromatography‐flame ionization detector analytical method for the analysis of epoxy fatty acids. Journal of Chromatography A 1318: 217–225.
  32. Muhl, M., Demisch, H.U., Becker, F., and Kohl, C.D. (2000). Electronic nose for detecting the deterioration of frying fat – comparative studies for a new quick test. European Journal of Lipid Science and Technology 102: 581–585.
  33. Ng, C.L., Wehling, R.L., and Cuppett, S.L. (2007). Method for determining frying oil degradation by near‐infrared spectroscopy. Journal of Agricultural and Food Chemistry 55: 593–597.
  34. Ng, C.L., Wehling, R.L., and Cuppett, S.L. (2011). Near‐infrared spectroscopic determination of degradation in vegetable oils used to fry various foods. Journal of Agricultural and Food Chemistry 59: 12286–12290.
  35. Osawa, C.C., Gonçalves, L.A.G., and da Silva, M.A.A.P. (2013). Odor significance of the volatiles formed during deep‐frying with palm Olein. Journal of the American Oil Chemists' Society 90: 183–189.
  36. Petersen, K.D., Jahreis, G., Busch‐Stockfisch, M., and Fritsche, J. (2013). Chemical and sensory assessment of deep‐frying oil alternatives for the processing of French fries. European Journal of Lipid Science and Technology 115: 935–945.
  37. Ravelli, D., Matsuoka, C.R., Della Modesta, R.C. et al. (2010). Determination of deep frying soybean oil disposal point by a sensory method. Journal of the American Oil Chemists' Society 87: 515–520.
  38. Robertson, C.J. (1968). A review of deep frying current practices point the way to new horizons. Canadian Institute of Food Technologists Journal 1: A66–A75.
  39. Sanibal, E.A.A. and Mancini‐Filho, J. (2004). Frying oil and fat quality measured by chemical, physical, and test kit analyses. Journal of the American Oil Chemists' Society 81: 847–852.
  40. Stevenson, S.G., Vaisey‐Genser, M., and Eskin, N.A.M. (1984). Quality control in the use of deep frying oils. Journal of the American Oil Chemists' Society 61: 1102–1108.
  41. Stier, R. (2001). The measurement of frying oil quality and authenticity. In: Frying: Improving Quality (ed. J.B. Rossell). Cambridge: Woodhead Publishing.
  42. Stier, R.F. (2004). Tests to monitor quality of deep‐frying fats and oils. European Journal of Lipid Science and Technology 106: 766–771.
  43. Stier, R.F. (2013). Ensuring the health and safety of fried foods. European Journal of Lipid Science and Technology 115: 956–964.
  44. Tompkins, C. and Perkins, E.G. (1999). The evaluation of frying oils with the p‐Anisidine value. Journal of the American Oil Chemists' Society 76: 945–947.
  45. Velasco, J., Marmesat, S., Bordeaux, O. et al. (2004). Formation and evolution of monoepoxy fatty acids in thermoxidized olive and sunflower oils and quantitation in used frying oils from restaurants and fried‐food outlets. Journal of Agricultural and Food Chemistry 52: 4438–4443.
  46. Weisshaar, R. (2014). Quality control of used deep‐frying oils. European Journal of Lipid Science and Technology 116: 716–722.
  47. Xu, X.‐Q. (1999). A modified VERI‐FRY® quick test for measuring total polar compounds in deep‐frying oils. Journal of the American Oil Chemists' Society 76: 1087–1089.
  48. Yang, M., Chen, Q., Kutsanedzie, F.Y.H. et al. (2017). Portable spectroscopy system determination of acid value in peanut oil based on variables selection algorithms. Measurement 103: 179–185.
  49. Yee Foo, S., Cuppett, S., and Schlegel, V. (2006). Evaluation of SafTestTM methods for monitoring frying oil quality. Journal of the American Oil Chemists' Society 83: 15.
  50. Zeb, A. and Ullah, F. (2016). A simple spectrophotometric method for the determination of Thiobarbituric acid reactive substances in fried fast foods. Journal of Analytical Methods in Chemistry 2016: Article ID 9412767, 5 pages.
..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.
Reset
3.135.183.89