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The science of producing the ‘perfect French fry’

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

The article analyzes the technical aspects of making ‘the perfect French fry’, specifically examining the importance of potato varieties, frying oil, and the blanching process.

Understanding the Role of Potato Varieties

Potatoes are one of the most nutritious foods in the world, rich in minerals, fiber, vitamins, starch, protein, and more. However, the nutritional composition changes with different processing techniques.

French fries are one of the most popular products in the world, with their attractive yellow-gold color, good taste, aroma, and characteristic texture. Their sensory quality has become increasingly important over the years, but there is now more emphasis on producing healthier French fries due to the risk of diseases such as obesity, high blood pressure, and high cholesterol levels associated with the high-fat content of French fries.

In addition, high heat and exposure to oxygen degrade essential nutrients and create carcinogenic molecules such as acrylamide. Therefore, it is critical to determine how the nutrient composition of specific potato varieties changes during processing, along with their sensory characteristics, to determine variety suitability for commercial French fry production.

On the other hand, water and starch are the most critical compounds in potatoes. The dry matter of potatoes, mainly composed of starch, is a characteristic that depends on several factors, such as planting time, soil moisture, harvesting time, and physiological age of the tuber.

All of these factors influence their nutritional value and flavor, and especially the texture of the processed product. The roasting process can cause changes in the structure of nutrients such as proteins, vitamins, and antioxidants.

As mentioned above, some compounds produced during the frying process, such as acrylamide, are a public health concern. This means that the levels of acrylamide in foods should be reduced to as low a level as reasonably achievable. Acrylamide formation depends on many factors, such as the amount of reducing sugars and free asparagine (depending on the potato variety), the cooking process, the temperature and time, the pH, and the surface-to-volume ratio of the food materials.

Selecting potato varieties that are rich in nutrients can contribute to producing French fries that are not only tasty, but also healthy by being low in fat and harmful substances, while also providing good nutrition.

In 2020, the Institute of Food Science and Technology in China evaluated ten potato varieties suitable for frying, examining their nutritional, functional, and safety properties.

The study showed that each potato variety reacted differently to the frying process, with moisture, ash, protein, carbohydrates, vitamin C, and sugar content decreasing in some, while fat, fiber, vitamin E, and acrylamide increased in others.

Although nutrient loss is inevitable when frying, efforts should be made to retain as much of the nutritional value as possible.

Choosing the Right Oil

Frying is the most traditional and widely used method for cooking potatoes. However, the process alters their physical, chemical, and sensory characteristics, with oil content, color, and texture being their primary quality parameters. Frying enhances the taste and overall palatability of chips and fries, but it also increases their fat content, which has been linked to obesity, high blood pressure, and cholesterol levels.

In response to growing consumer demand for low-fat or fat-free potato products, numerous studies have been conducted to develop and optimize methods to reduce oil absorption in fried chips and French fries. Many food processors are investing resources in producing fried potatoes with low oil content while maintaining their desired flavor and texture. Color, texture, and oil content are considered the most critical quality parameters for the potato chip and French fry manufacturing industries.

A 2018 study by researchers at Jiangsu University in China summarized the findings of several studies on fat absorption in potato chips and French fries. According to the researchers, polymerization reactions during frying can degrade the oil and increase its viscosity, leading to faster absorption into the French fries or chips. Frying oil enriched with oleic acid may be a good option as a frying medium.

For them, the factors affecting oil absorption are complex and interrelated. Two-stage frying and vacuum frying may be better choices to reduce fat absorption. Since fat absorption is a structural phenomenon, the structural properties of potato chips are important.

The application of biopolymer coatings to reduce the evaporation rate and void formation is helpful to reduce oil absorption.

They concluded that future studies should focus on mitigation strategies for problems related to the reduction of sugar, acrylamide, and acrolein formation in combination with oil reduction using novel air frying.

The Science Behind Blanching for Crispy French Fries

As mentioned above, the quality of French fries is characterized by their texture, oil and moisture content, color, taste and food safety. Among these, texture has been recognized as one of the most important quality aspects of French fries.

In the production line of French fries, the blanching process is indispensable for the development of an appealing French fry with good quality in terms of texture and color. During the frying process, blanching pretreatment can promote starch gelatinization and form a gel layer on the surface of French fries to reduce oil absorption.

Blanching also softens the French fries by gelatinizing the starch and solubilizing the pectin. It also effectively reduces the concentration of glucose and asparagine in potato slices, which significantly reduces the formation of acrylamide during frying.

However, blanching has several drawbacks, including slow heat transfer, long processing times, significant loss of soluble nutrients, and high water consumption. Therefore, researchers are combining new technologies with traditional processing methods to achieve better results.

In 2021, researchers at Jiangnan University (China) investigated the effects of combining pulsed electric field (PEF) with blanching pre-treatment on the physio-chemical properties of French fries.

The researchers found that this pretreatment significantly affected the physicochemical properties of the resulting French fries compared to either a single pretreatment or no pre-treatment.

It also increased electrolyte leakage from the potato strips and resulted in a more aesthetically pleasing, brighter and golden yellow final color. The fries were also less hard.

In Summary

Photo by Jonas Allert on Unsplash

Producing the perfect French fry requires a deep understanding of the technical aspects of the process. Factors such as potato variety, frying oil and blanching are critical to achieving the desired texture, color and flavor while ensuring food safety and nutritional value.

The nutritional composition of potato varieties changes during processing. Therefore, selecting varieties with a high nutritional composition can help produce French fries that are not only of good sensory quality, but also more nutritious.

Frying oil plays an important role in determining the amount of fat absorbed. Several studies have been conducted to optimize methods to reduce oil absorption while maintaining the desired taste and texture.

The blanching process is also critical to producing quality French fries in terms of texture and color. Although blanching has several drawbacks, including significant loss of soluble nutrients and high water consumption, it remains an essential part of the production line.

Overall, the production of perfect French fries requires a balance between technical knowledge and innovative approaches to mitigate potential health risks associated with the consumption of this popular snack food.

Author: Jorge Luis Alonso G. is an information consultant specializing in the potato crop. He writes marketing materials for Ag-Tech companies.
Cover photo: Credit Ekaterina from Pixabay

Editor & Publisher: Lukie Pieterse

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