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Study: Comparison of frying methods’ impact on chemical formation in French fries

This article was written by Jorge Luis Alonso G., an information consultant specializing
in the potato crop.

Deep-fat frying, a cooking technique that involves immersing food in hot oil, has been linked to several potential health problems due to the formation of toxic compounds during cooking.

One such compound, acrylamide (AA), found in high-carbohydrate foods like French fries, has been linked to potential human carcinogens. Another compound, hydroxymethylfurfural (HMF), can form during cooking and has been linked to health problems.

To address these concerns, new frying methods such as microwave frying, air frying, and vacuum frying have emerged. Vacuum frying, in particular, has been shown to produce potato fries with lower levels of AA compared to atmospheric pressure frying.

Researchers at the University of Allahabad (India) has published the results of a study in this regard in the journal Innovative Food Science and Emerging Technologies.

The objectives of this study were (I) to investigate the effect of different frying processes on French fries, focusing on their texture, color and sensory evaluation, (2) to study the physicochemical properties of the oil extracted from these French fries, and (3) to identify alternative frying methods that would reduce the intake of toxic substances while maintaining desirable properties in fried foods.

For their experiment, the team used a mechanical cutter to make fries from a 15kg potato batch. Each frying method — deep frying, microwave frying, vacuum frying, and air frying — was performed using different equipment, temperatures, and frying times.

To assess the quality of those samples, the study focused on three key factors: asparagine content, moisture content and color values. The team analyzed asparagine content using a spectrophotometer, calculated moisture content by drying the samples and measured color using an Xrite colorimeter.

The research team found that the moisture content decreased with increasing temperature and frying time for all frying methods except microwave frying. This is due to the electromagnetic field heating of the microwave method, which leads to higher moisture retention. Air frying resulted in the highest loss of moisture content, while deep fat frying required a greater driving force for heat transfer. In terms of fat content, deep frying had the highest amount, while air frying had the lowest. Atmospheric frying had the highest oil uptake, while air frying had the lowest.

Scientists also observed that high temperatures and longer frying times resulted in higher a* (green to red) and browning index values and lower L* (blue to yellow) values. Vacuum and air frying produced a lighter color than atmospheric and microwave frying.

The research team also looked at the formation of harmful compounds during frying. Increasing time and temperature during frying resulted in greater production of HMF and AA. Vacuum frying had the highest percentage reduction in HMF, while air frying had the lowest formation of AA. In addition, peroxide and anisidine levels increased with frying time and temperature, with deep frying producing the highest levels of these compounds. The Dinitro-salicylic acid (TOTOX) value, which is the sum of the peroxide and anisidine values, increased with increasing temperature and frying time.

Overall, this study provides valuable insight into the effect of different frying methods on the quality characteristics of French fries and the formation of harmful compounds during frying.

According to the paper, deep-fried and microwave-fried samples of French fries had higher levels of HMF and AA than air- and vacuum-fried samples. The study also found that AA and HMF levels increased with time and temperature in deep-fried and microwave-fried samples.

However, for air-fried samples, a combination of high temperature and short time resulted in the lowest levels of AA and HMF. Besides, the texture and acceptability of vacuum- and air-fried French fries were superior to those of deep-fried and microwave-fried samples.

Therefore, vacuum and air frying methods can be considered effective solutions to the problems associated with high AA levels, darkening of color, and high oil content in French fries. By using these alternative frying technologies, food manufacturers can reduce processing toxicants and cut oil consumption.

Source: Vandana Verma, Vijayta Singh, Om Prakash Chauhan, Neelam Yada. Comparative evaluation of conventional and advanced frying methods on hydroxymethylfurfural and acrylamide formation in French fries. Innovative Food Science & Emerging Technologies. Volume 83, 2023.
Author: Jorge Luis Alonso G. is an information consultant specializing in the potato crop. He writes marketing materials for Ag-Tech companies.

Editor & Publisher: Lukie Pieterse

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