Mapping traditional fries (slapchips) from eleven potato varieties (2024)

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Müller C,

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Sconfeldt HC, Hall N, Pretorius B

Department of Animal and Natural Sciences, University of Pretoria, South Africa

Correspondence:Carmen Muller, Department of Animal and Wildlife Sciences, Department of Food, Nutrition and Welfare, University of Pretoria, Lynnwood Road, Pretoria, Gauteng, South Africa, Tel. +2773-1551095, fax 086-516-6377

Received:2 november 2016 |Published:4 mei 2017

Quote:Muller C, Scönfeldt HC, Hall N, et al. Mapping traditional French fries (slapchips) from eleven potato varieties.J Nutr Health Food Eng. 2017;6(3):88-98. DOI:10.15406/jnhfe.2017.06.00203

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"Slap chips" are a traditional South African product widely consumed throughout the country. These chips are similar to French fries, but are thicker and fried longer at a lower temperature using a double frying method. It is believed that the different textural characteristics of potatoes will mean that certain varieties are better suited for frying than others.

As part of this study, a market survey was conducted to better understand weak chip production methods in order to develop a repeatable weak chip preparation method that simulates market conditions. Chips produced using this method were evaluated by a trained sensory panel to determine sensory properties for aroma, appearance, taste, texture and aftertaste.

A standardized preparation method was developed for the production of weak chips. Statistical analyzes showed that waxy and oily characteristics grouped cultivars together, while dry matter, fried chips, and earthy flavors distinguished chips from different cultivars. Under the current South African potato classification system, no clear grouping of varieties within the same class was found. It can be concluded that frying has such a great influence on the chip properties that cultivar-specific properties have less influence on the properties of the end product. However, certain properties, such as the dry matter, can influence the absorption of tuber oil.

Keyword:potatoes,Potato,slack chips, fries, varieties, sensory panel, frying, cooking

In South Africa, 17% of potatoes produced by farmers are used by the formal processing industry. This figure excludes fresh potatoes that are purchased and then processed by street vendors, corner cafes and takeaways. It is estimated that more than 50% of potatoes produced in South Africa are consumed by the informal market, a large consumer market comprising 46% of the South African population.^1,2

Potatoes are considered a highly biodiverse crop as several cultivars are grown and readily available in the market. Not all potatoes yield a uniform end product (cooked/prepared) due to species differences (dry matter), agronomic conditions (irrigation or dry soil), storage and seasonal planting, and inherent textural differences due to variations between cultivars.³This requires a classification system to categorize potato varieties based on their eating quality, enabling communication and increasing satisfaction from farm to fork.

The current South African potato classification system was implemented in 2008. The system classifies different potato varieties based on their ideal cooking categories, i.e. cooking, frying, chipping (baking in the oven), microwaving, pureeing and keeping its shape while cooking. The current classification system does not include a category for weak chips.⁴A need was therefore identified to include limp chips, as a culturally popular cooking method for potatoes, in this classification system.¹

South African slap chips

Slap chips are widely consumed in South Africa and are usually sold by street vendors and in corner cafes and takeaways, which are generally considered the informal market.⁵Slap chips differ from French fries because they are thicker, have a softer exterior, a creamy interior, and are "limp" or pliable when cooked. They are baked at a lower temperature for a longer period of time, which can lead to a fattier end product with a greasy mouthfeel.⁶ Chips have a thickness of 1 cm x 1 cm or slightly thicker and have an average length of 7 cm^7,8and baked at temperatures between 110°C and 160˚C. Fries are thinner with an average thickness of 0.6×0.6 cm and an average length of 4-5 cm. Fries are fried at a temperature of 180±5˚C for 4.0±0.3 minutes.⁹

Global consumption of fried foods is increasing rapidly; with jacket potatoes being one of the most consumed products.¹⁰According to the European Union report on potato production, "the significant increase in the consumption of processed potato products has increased mainly due to the corresponding increase in the demand for French fries."¹¹Different generations have different food preferences, which leads to such increased consumptionFigure 1. People currently entering the consumer market have a greater preference for fried and processed foods.¹²Consumers also have a greater preference for certain types of potato varieties. As stated intable 1different potato varieties have different sensory and cooking properties that have an effect on the cooked product.¹³

The purpose of the study

This study was conducted in an attempt to classify slack chips made from the 11 different types of cultivars most commonly consumed in South Africa. The purpose of the study was to determine whether certain potato subspecies are better suited for making weak potato chips than others, given their unique textural characteristics. Because there is very little or no data available on the preparation of slapchips, there are no scientifically validated guidelines available on the cooking method for preparing slapchips.

Therefore, the first objective of the study, which was to identify a standardized method for manufacturing weak chips, was investigated and a pilot study was conducted and standardized. Once the method had been developed and standardized, a trained descriptive sensory panel was used to extrapolate the second aim of the study, which was to describe the weak chip qualities of eleven South African potato varieties.

Methodical

When preparing chips, as with most other foods, there are a number of factors that influence the final product consumed (such as variety, cultivation, etc.). For this study, the most commonly consumed varieties in the South African market were identified to obtain a representative sample of all the different texture classes found in potatoes, as shown in Table 1. There are also different cooking methods used worldwide to prepare chips, therefore it is considered necessary to develop a standardized method for evaluating slack chips in the South African context.

Marketing research

To ensure that the research was true to market conditions, a pilot study was conducted to understand the requirements of this market. A number of different slap chip suppliers were visited in three different areas in South Africa; rural (Limpopo), suburban (Vaal Triangle) and urban (Pretoria) areas and asked about the methods they use to prepare limp fries, especially in terms of the cooking techniques used.

The pilot study showed that suppliers purchase 10 kg bags of fresh potatoes, often the bags available at the lowest price (the most affordable variety at the time was Mondial). Potatoes were peeled with hand peelers and immersed in water until cut, a largely manual process. After all the potatoes needed for the day were cut, they were removed from the water and placed on a towel to drain the excess water. The air-dried chips were fried in a pan or a metal drum at a low temperature, between 90˚C - 140˚C, before frying with sunflower oil for the first time. The cooking process took between 10 and 30 minutes. When the raw chips are placed in the oil, a temperature drop occurs, which increases the cooking time because the oil must be reheated. It was therefore difficult to estimate the exact temperature and time that suppliers used, as they prepared different batch sizes and used different amounts of oil.

After the first frying, the chips are removed from the oil and placed on a cloth or paper towel to drain excess oil. These chips are then ready for the second baking. The second round of frying takes place when the consumer buys the chips. The fries are fried in small batches at temperatures between 100˚C-140˚C and served directly to the customer.

Final roasting method

Based on the market research, a standardized frying method has been developed to ensure that the fries in the study resemble those on the informal market as much as possible. A double frying method was used to cook the slap chips. The potatoes were peeled and cut into slices with an average size of 1 cm × 1 cm and an average length of 6 cm and immersed in a 2.5% (v/v) sulfur dioxide mixture to prevent browning. The raw chips were dried on a cloth and then placed in hot sunflower oil, heated to 120°C for 5 minutes, removed from the oil and cooled to room temperature on the cloth. When the fries reached room temperature, they were fried a second time at 120˚C for 3 minutes and served immediately.

Methodical

Sampling

The potatoes used in this study were planted in the Reitz area of ​​the Eastern Free State, South Africa, one of the most productive dryland potato production areas in the country. The potatoes of the different varieties were supplied by Potatoes South Africa, planted on the same day under dry conditions in the same field in the summer of 2012/2013. The tubers were harvested on April 11, 2013. The tubers were not washed, but packed directly from the ground in cultivar-specific bags and transported to the Agricultural Research Council (ARC) Irene, Pretoria, within 24 hours of harvest. The tubers were placed in pre-marked boxes in a dark room at room temperature (20°C) until the slap chips were prepared. The textural characteristics of the selected cultivars are shown intable 1.

Sample preparation

The slap-chip samples were prepared according to the developed standardized methodology. Every day, 5–7 tubers of each cultivar were washed, dried and weighed. The tubers were peeled, cut and placed in a bucket containing a mixture of 2.5% (v/v) sulfur dioxide and water. The chips were cut lengthwise into 1 cm x 1 cm sticks with an average length of 6 cm. The chips were allowed to sit in the sulfur dioxide mixture for 30 minutes to reduce browning. After 30 minutes, the chips were washed under running tap water for 10 seconds to remove excess sulfur dioxide and allowed to drip. The six center fries were pre-fried in a Delonghi Roto Fryer in the preheated frying oil at 130˚C to ensure that when the fries were placed in the oil, the temperature dropped to the desired 120˚C for frying for 5 minutes. The Delonghi Roto Deep Fryer ensures that the basket containing the fries is immersed in oil and continuously rotated to achieve even frying. The oil was kept at the same temperature throughout the fryer. Excella sunflower oil was used to fry the chips because it is the oil that the sellers in the pilot study identified as the oil they use most often.

Oil temperature was measured continuously using a portable stainless steel digital probe equipped with a J-type thermocouple. The fryer lid was not used to simulate market conditions and to allow constant temperature measurement. After frying for 5 minutes, the chips were removed from the oil and placed on paper towels to absorb excess oil. After cooking, the chips had an internal temperature of 84˚C.

The pre-baked chips were allowed to cool to a room temperature of 23˚C to simulate market conditions. For the second frying, the same procedure was followed as for the pre-frying process, but the fries were fried for only 3 minutes and when they were removed from the fryer, the excess oil was removed by shaking the basket. The chips were placed on paper towels to absorb excess oil. The chips were then wrapped in 10cm x 15cm aluminum foil envelopes to ensure they retained heat. This also allows them to steam to simulate market conditions. The aluminum foil envelopes were each pre-coded with a random three-digit code. These envelopes of chips were placed in a preheated oven at 115˚C on a baking tray. After 5 minutes, the chips were removed from the oven and served to the panel on a preheated plate heated in a preheated oven at 60°C.

Samples were given to panelists through individual cabinet doors. In addition to the aluminum foil envelope with chips, the panel received an evaluation form, a pencil, an eraser and a napkin. Also present were water, carrot slices (used as a palate cleanser) and an encyclopedia that was already in the tasting booth. Starting at 9 a.m., the panel tasted 11 samples over 4 sessions per day for 4 days. The first, second, and third sessions each included three taste samples, and the last session of each day included two samples. The samples were served to the panel at 10-minute intervals, with a 15-minute break between sessions.

Testing facilities

All samples were evaluated according to the methods described in the Annual Book of ASTM Standards. The sensory analysis facilities are equipped with all the elements necessary for an effective sensory program and are built according to ASTM design guidelines for sensory facilities.

Panelists assessed the products one at a time (four sessions per day) in separate tasting booths to reduce distraction and interaction with panelists and to ensure uninterrupted, unbiased, individual responses. Once completed, each panelist's score sheets were collected individually and data was recorded directly from the score sheets into an Excel worksheet.

The entire chip was evaluated under white light conditions. White lighting conditions are used to ensure that the product has a natural appearance.

Sensory evaluation

Twelve experienced panelists were selected to participate in this study. These panellists had all previously trained at the Agricultural Research Council Sensory Unit in Irene. The panelists were selected based on their acuity of taste and smell, interest, ability to distinguish between the five basic tastes (sweet, sour, salty, bitter and umami) and availability for the entire study. The panelists have been involved in numerous sensory evaluations of foods such as meat and meat products, fats and oils, dairy products, potatoes, beverages and more.

Prior to the tasting, panel members for this study participated in a general training program consisting of four sessions to:

1. Develop appropriate descriptive terminology for slap chips that can be used in the lexicon
2. Train, familiarize, and test panelists in the use of the evaluation scales that have been constructed
3. Develop and finalize rating scales and terminology to be used.

During the training, panelists were exposed to different potato varieties and asked to analyze them and develop descriptive sensory terms that were used in the final evaluation lexicon (table 2). Thybo and Martens' lexicon was used as a reference point and adapted to include the attribute descriptions suggested by the panelists.¹⁴These descriptive words included aroma, non-oral texture, oral texture, and taste and aftertaste characteristics of the weak chip samples. A category scale was constructed with one (1) indicating the least favorable condition (none: e.g. no clean/fresh oil aroma) and eight (8) indicating the most favorable condition (e.g. extremely intense clean/fresh oil aroma).attachment 1) and is used to evaluate the different samples. To ensure that the panelists were not influenced in any way, no detailed information was provided about the purpose of the project.

Objective evaluation

The dry matter analysis of the tubers was carried out gravimetrically according to the AOAC 934.01 method. Specific gravity was determined by weighing five tubers individually as they are, followed by an underwater weighing in which the tubers are placed in a net and immersed in water. The density is then calculated using the following equation:¹⁵

$SSeCIFICGR\mathrm{-in}vITj=\frac{WeIGHTIN\mathrm{-in}IR}{\left(WeIGHTIN\mathrm{-in}IR-WeIGHTuNDeRw\mathrm{-in}TeR\right)}$

Statistical analysis

The data was recorded using an Excel spreadsheet. The data was checked for outliers using a residual test.

Quantitative descriptive data for all attribute scores were subjected to analysis of variance (ANOVA) using statistical software GenStat.¹⁶An analysis of variance was performed to determine differences between cultivar effects at the 5% level. GenStat's Partial Least Squares (PLS) regression procedure was used to determine which of the set of correlated objective (X-matrix) variables and 11 cultivars were used to determine the variation in the sensory profile (Y-matrix) of loose chip potatoes and explain.

Grouping of potato varieties based on weak chip quality

From ANOVA-analysis (Table 4) showed significant differences (p≤0.05) for 14 of the 17 sensory traits between the different cultivars. Significant differences were seen in scores for aroma, non-oral texture, oral texture, taste and aftertaste characteristics of chips from the eleven varieties, with the exception of earthy aroma, earthy taste and earthy aftertaste. In the future, soil/soil properties can be removed from the taste panel form and no longer need to be measured as a property. Frying food can significantly change the texture and taste of food. Certain textural and flavor aspects already present in the tubers can be improved and others reduced during the roasting process.¹⁷The textural appeal of a potato has a critical impact on potato acceptance and is a dominant indicator of quality among consumers.¹⁸

Since there is no significant difference in the texture of the different weak chips, it can be assumed that all varieties are texturally acceptable to consumers. However, no clear pattern of differences between cultivar types (waxy, waxy/mealy, mealy) emerged for any of the properties, indicating that there are no significant differences in textural properties between the different classes of tubers in the current classification system. Although no single cultivar performed significantly better than the rest, seven (Mondial, BP1, Bp13, Van Der Plank, Fabula, Valor, Avalanche) of the eleven cultivars had overall higher values ​​for typical fried chip flavor and typical fried chip aroma. This may indicate that they may be better suited for the preparation of weak chips.

Aroma is an important aspect of fried foods because aroma is associated with the texture and taste of the food prepared in this way.¹⁹All varieties had a typical fried chip aroma (p<0.001), except Fianna and Sifra, which had a low typical fried chip aroma and aftertaste.

When assessed for appearance, Mondial, Fabula, VDP, Sifra and Avalanche had an oily surface (p<0.001), with BP1, Darius and UTD differing significantly with a low oily surface. BP13 and Darius had a high breaking ease (p<0.001) and Valor a low breaking ease.

The texture of Mondial, Fabula, VDP, Sifra and Avalanche in the chip was higher (p<0.001) and BP1 lower. This is similar to the results for an oily surface. BP13, BP1, Valor, UTD and Darius had a mealy texture (p<0.001) and Mondial, Fabula, VDP, Sifra and Avalanche had a waxy texture (p<0.001). All cultivars except BP1 and Valor had high grain texture (p=0.031).

Overall fattiness (aroma, texture, taste and aftertaste) was lowest in Darius, with few statistical differences observed between Darius and BP1, BP13, UTD and Valor. Although dry matter (Table 4) was high for both Fianna (27.3) and Darius (26.5), appears to have affected oil absorption in Darius to a greater extent. Mondial, Fabula, BP1, VDP, Valor and Avalanche had a high typical fried chip taste (p<0.001). Darius had a low, typical fried chip taste. Mondial, Fabula and Avalanche had high oily (p<0.001) and bitter (p=0.006) taste and BP1 and Darius had low oily taste, while Valor had low bitter taste. Fabula, UTD, BP1, Fianna and Sifra also had high bitter aftertaste (p<0.001).

Mondial, BP1, Valor and Avalanche had a typical aftertaste of fried chips (p<0.001), and Fianna and Sifra had a low typical aftertaste of fried chips. Mondial, Fabula, Sifra, Avalanche and VDP had a high oily aftertaste (p<0.001) and Darius had a low oily aftertaste, Darius also had a low oily aroma (p<0.001).

Mondial and Fabula had high values ​​for most attributes. Avalanche had high values ​​for odor and taste properties. Darius had low taste values. There was no significant difference in the earthiness of the smell, taste and aftertaste of the chips (p > 0.05).

Connection between qualities

A single correlation matrix was constructed to identify correlations between attributes identified by the taste panel. A correlation of 0.8 and above indicates a significant correlation and a correlation of 0.6 and above indicates a fair correlation.²⁰

Strong associations were found between all aspects of adipose tissue. The oily texture correlated with the oily aroma (r=0.7820) and strongly with the oily appearance (r=0.8760), oily taste (r=0.8859) and oily aftertaste (r=0.8480). . Frying potatoes for a long time at a low temperature can significantly affect the amount of oil absorbed.¹⁰This cooking method produces an overall oily final product.

An oily texture correlated positively with a waxy texture (r=0.7882), while it correlated negatively with a mealy texture (r=-0.8201). This indicates that limp chips with a waxy texture appear oilier than limp potato chips with a floury texture. Potatoes with higher moisture and lower solids (waxy substances) have been repeatedly shown to absorb more oil during frying because more moisture is lost during cooking, giving the chips a fattier appearance and taste . For this reason, floured potatoes are generally preferred when preparing French fries.^6,21

It turned out that if a potato looked greasy, it had both an oily taste (r=0.9049) and an oily aftertaste (r=0.9423). A very strong negative correlation was observed between the texture of floury and waxy potatoes (r=0.9813), indicating that there was a significant difference in the textural characteristics of the different varieties. A study of cooked potatoes found that mealy qualities are among the easiest sensory qualities to be assessed by a potato sensory panel.²²In this study, panelists were also able to identify the difference between waxy and mealy, limp chips.

Waxy potatoes had a strong correlation with an oily aftertaste (r=0.8241), while floury potatoes had a negative correlation with an oily aftertaste (r=-0.8241). A chip with an oily taste has a high chance of an oily aftertaste (r=0.9619). A survey of consumer preferences found that American consumers prefer chips that do not have an oily aftertaste and appearance.²³Fries with a typical fresh potato aroma also had a typical fried french fries taste (r=0.8204) and a typical fried aftertaste (r=0.8490).

Dry matter and density correlated less with each other than expected at r=0.6831. A study conducted in America in 1975 showed that there was a strong correlation (r=0.912) between the specific weight and the dry matter content of 1,269 tubers.²⁰In a study conducted in Pakistan, a correlation of r=0.5966 was observed between dry matter and specific gravity.²⁴There are generally significant differences in the relationship between specific gravity and dry matter in potatoes from different countries. These differences may be due to different cultivars and agronomic methods used in different countries.

Specific gravity is one of the most commonly used methods in the potato industry to determine the cooking and shredding quality of tubers, as specific gravity is a determining factor for textural properties and cooking quality.¹The specific gravity determines the total dry matter and dry matter in a potato tuber.¹⁵

Dry matter is considered more reliable because it is a scientifically repeatable evaluation method. Dry matter is measured by drying a known wet weight finely chopped tuber, placing it in a drying oven to extract all moisture from the meat and then weighing it again to determine the total dry matter content.²⁵

Because specific gravity measurements are easier to obtain, they are more often the preferred method of evaluation. Oregon State University has developed a specific density and dry matter reference guide that outlines the relationship between density and dry matter. Specific gravity measurements usually fall within the range between 1.055-1.095 with correlating values ​​for solids between 16.5% and 24%.^26,27A study conducted in Pakistan found that the specific gravity of 32 different potato varieties ranged between 1.0343 and 1.1443.²⁴which is a wider and higher range than the average values ​​of European potatoes. Again, this may be due to the different cultivars and agronomic methods used in different countries.

Dry matter correlated with the typical taste of fried chips (r=-0.6634) and earthy taste (r=-0.6259). The specific gravity correlated with the typical taste of fried chips (-0.6634), earthy taste (-0.6259), oily taste (-0.6675) and oily texture (r=0.8386).

The typical aroma of freshly fried fries correlated with the typical taste of fried fries (0.8204) and the typical aftertaste of fried fries (0.8490). The typical aftertaste of fried fries had a strong correlation with the typical taste of fried fries (0.9665).

Both specific gravity and dry matter had a low correlation with flour (r=0.5327; r=0.1836) and waxy texture (r=-0.4331; r=-0.0271), indicating that no of these criteria can be used in the case of weak chips. as a determinant of the mealy or waxy texture observed in sensory tests. A survey of consumer preferences found that baked potatoes with a low specific gravity and therefore a waxy texture were preferred over baked potatoes with a floury texture based on their texture. But floury potatoes were preferred because of their taste.²⁸

The first two dimensions of PLS ​​(SC1 and SC2) accounted for 95.41% of the data, 83.71% were declared in the first dimension and 11.70% were declared in the second dimension with latent roots of 72, 66 and 10.16 (must be >1 significant).

In the first dimension (SC1), the positive loadings were generally the taste of fried chips (r=0.669), earthy taste (r=0.620); and dry matter (r=-0.999), shown as a negative charge. These properties of the first dimension explain the different grouping of Fabula and UTD versus Sifra, BP1, BP13 and Darius.

The variance in the second dimension (SC2) had negative loadings for mealy texture (r=-0.965) and positive loadings for waxy texture (r=0.984), oily appearance (r=0.915), oily aftertaste (r=0.871), oily taste (r=0.807 and oily aroma (r=0.743).²⁹

The waxy texture and oily appearance, oily aftertaste and oily taste contributed to the grouping of Fianna, Mondial, Valor, Sifra and Buffelspoort (BP13), as opposed to UTD, VDP, Avalanche, Darius and BP1.

Table 5Percentage of variance explained in the first and second dimensions for sensory properties and objective tests performed on slapchips made from eleven different cultivars

Currently, the potato classification is mainly determined by measuring the specific weight of a variety. Specific gravity is a relatively poor indicator (r=-0.228) of texture, but it appears that solids content can provide more accurate results (r=-0.999) for chips.^30,31

The percent variance (PLS) as explained inTable 5shows that dependent variables (sensory properties) are mainly explained by oral similarity in the second dimension, while no sensory properties explain the variance in the first dimension. Variance of the independent variables i.e. chemical analysis, was explained by the percentage of dry matter.

A standardized cooking method was developed to ensure that the weak chips tested in this study were true to market practice. The trained sensory panel that tested the slapchips found no clear grouping of varieties within the same class according to the South African potato classification system.

Fatness was one of the main differentiating factors between cultivars. Chips that looked greasy had an oily taste, aroma, feel and aftertaste. Darius was the cultivar with the lowest score for oily properties. However, there was no clear difference between the types of cultivars (waxy, waxy/mealy, mealy) in terms of sensory properties, indicating that there is no significant difference in the textural properties of the tubers when fried. However, certain cultivars scored higher on the typical traits of slack chip, including Mondial, BP1, BP13, Van Der Plank, Fabula, Valor and Avalanche.

It can be concluded that frying has such a great influence on the chip properties that cultivar-specific properties have less influence on the properties of the end product.

It is recommended to test the preference for different cultivars among typical consumers of slack chips.

Name:Day: 4 (April 19) Session: 3.

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