Food Lipids: Chemistry, Nutrition, and Biotechnology

flavor if properly processed. This low intensity of flavor continues during the early
portions of the frying cycle because the typical fried flavor develops as heating and
frying time increase. Food processors often heat oils or fry preliminary batches of
food to condition the oil to develop this flavor. Some oils develop this characteristic
deep fried-food flavor more quickly than others depending on the fatty acid composition
of the oil. For example, Warner et al. [48] found in previous research that
cottonseed oil with high (50–55%) linoleic acid produces significantly higher intensity
of fried-food flavor in potato chips and french fried potatoes than do oils with
low (10%) linoleic acid, such as high (80–90%) oleic oils. As the fatty acids decompose
in high temperature conditions, the volatile degradation products produce
characteristic flavors. Some oxidation products, such as 2,4-decadienal, are important
in the formation of typical deep-fried flavor. Flavor improves after the first stage of
frying and becomes less acceptable during the last stage. Frying conditions should
be adjusted so that optimal flavor characteristics are maintained for as long as possible
during the frying cycle.
Sensory evaluation is still the method most often used by different countries
to determine when to discard a frying oil [34]. Billek [33] reported that scientific
groups in Germany used sensory assessment of a used frying oil; however, if this
method did not give a clear indication that the oil was deteriorated, then instrumental
or chemical analysis was used to support a final decision on oil quality. More recently,
recommendations from the Third International Symposium on Deep Fat Frying
recommended that the principle quality index for deep-fat frying be sensory
parameters of the fried food [50]. To further confirm oil abuse, total polar materials
should be less than 24% and polymeric triglycerides less than 12% [50]. Sensory
analysis of frying oil and fried-food quality may be conducted by analytical descriptive/discriminative
panels using trained, experienced panelists [46–48,51] or by consumer
panels using untrained judges [34]. Melton used consumer panels to find that
the flavor likability of fried food is dependent on consumer perception and is affected
by the type of oil used for frying [34]. In further studies, Melton and coworkers
could find no differences in fresh chip flavor or likability scores between potato
chips fried in partially hydrogenated canola oil or cottonseed oil when evaluated by
a consumer sensory panel [44]. On the other hand, Warner found that a trained,
experienced, analytical descriptive panel could detect differences (P < 0.05) in the
type and intensity of flavors in fried food prepared in various oil types [48]. More
research is needed to understand the relationship between fried-food flavor and the
volatile and nonvolatile decomposition compounds produced in frying oils.
REFERENCES
1. C. W. Fritsch. Measurements of frying fat deterioration: A Brief View. J. Am. Oil Chem.
Soc. 58:272 (1981).
2. R. Moreira, J. Palau, and X. Sun. Simultaneous heat and mass transfer during the deep
fat frying of tortilla chips. J. Food Proc. Eng. 18:307 (1995).
3. M. M. Blumenthal. A new look at the chemistry and physics of deep fat frying. Food
Tech. 45:68 (1991).
4. J. C. Alexander, B. E. Chanin, and E. T. Moran. Nutritional effects of fresh, laboratory
heated, and pressure deep fry fats. J. Food Sci. 48:1289 (1983).
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