Investigation of the relationship between the textural characteristics of potato chips and mass transfer parameters of the oils used for frying

Potato is a substancial source for human nutrition and has superior nutritional value for human daily diet with carbohydrate, vitamins and fiber content. Considerable high harvesting yield of potato per unit area and easy adaptation to climatic conditions raises the importance and prevalence of the potato planting. 4000 m above sea level, potato is produced in a very wide area between the 70th north latitude and 50th south latitude. Potato are considered to be the fourth most produced crop after wheat, rice and corn. All over the world especially in developed countries consumption of the fresh potato showed a downward trend while the consumption of potato based fast food, snacks and ready food products showed an upward trend. Potato chips, nuts generally known as ''Snack Food'' are highly demanding by consumers around the world. In addition, potato flour, bread flour is mixed with a certain percentage (2.5-3.0%), the taste of bread increases and the stale is delayed. Potato starch is widely used in making salami and sausages. Both tubers and dried stems are used in animal nutrition. The chemical composition of potatoes is influenced by many factors such as production area, variety, soil, climate and agricultural practices. Among the factors that affect quality in potatoes are the specific weight and dry matter value of the tuber which is the most important of the food industry. It was determined that storage losses were low, reduced sugar accumulation was low and processed product yield was high in potatoes with high dry matter. In addition, the desired quality features vary according to the purpose of use. Potatoes consumed as meal, the protein and dry matter ratio are high and the distribution property is low. It is desirable to have high potato yield, low fat content and light color for chips and french fries. Frying is the process of cooking the food by immersing it in the edible oil at the temperature above the boiling point of water. Frying is a highly complex process due to simultaneous heat and mass transfer. As the high temperature in the oil is transmitted to the food, the water in the food evaporates from the food and the oil diffuses into the gaps formed by the water. At this stage, many physical, chemical and nutritional changes occur in foods. For this reason, frying is a process that is widely used in the production of processed potato products and provides the desired characteristics of the product as well as substances that adversely affect human health. Nowadays, consumer preferences are more healthy and low fat products. Therefore, one of the parameters to be considered in frying process conditions is oil absorption. Accurate understanding of the oil absorption mechanism is possible by mathematical modeling. Modeling is important in minimizing unwanted effects, process optimization, product development and shelf-life stability. The success of the model depends on the accuracy of heat and mass transfer parameters due to the difference in temperature and concentration during frying. In this study, textural properties of the potato chips, different type of vegetable oils as well as their mass transfer relation during the frying process are aimed to investigate. Hence, four different vegetable oil as sunflower oil, olive oil, corn oil and palm olein oil used for frying process, as a potato variety Brooke potato is used and for the model system potato starch anf cellulose are used. For the frying process, (2 ± 0.1 mm) potato slices are subjected to 180°C temperature and during the frying porcess, mass transfer from different type of vegetable oils to potato slice is calculated individually based on experimental methods and modelling also the correlation between textural feature and mass transfer of the potato chips is analyzed and the effect of the fatty acid compoiton on obtained results is discussed. In determining the mass transfer by modeling, the ability of the oil to diffuse into the model liquid composition formed by taking the basic components of the potato into account is demonstrated by dynamic light scattering technique. Experimentally, the mass transfer for the oil is calculated based on Fick's law (Fick's 1st law of diffusion). Soxhlet method is used to analyse the fat content of the chips and for the fatty acid composition gass chromatography is used, also punch test is carried out for stiffness (N), fracturability (N) and deformation (mm). Based on obtained results; the chips which are fried with sunflower oil showed lowest moisture content (%0,93) and highest fat content (%43,13), on the other hand the chips which are fried with palm olein oil showed the highed moisture content (%1,8) with lowest fat content (32,03). This is because, the fat absorbsion rate has a relation with the water evaporating from the product. While water is leaving from sturucture with evapotaion, pores are filling with oil at the same time. The effect of different oil types on moisture content investigated statistically, and similar results were obtained for other oil types except palm olein oil in moisture analysis (p<0,05). The effect of different oil types on fat content investigated statistically, it was seen that there was a significant difference in the effects of oil in fat analysis (p<0,05). It is thought that the heterogeneous distribution of starch and other components of potato on the variability of moisture, oil and textural results is related to texture parameters and frying environment after frying. When the fatty acid analysis results are examined, the saturated fatty acid composition is founded as; palm olein oil (%44,04), olive oil (%13,89), corn oil (%13,29) ve sunflower oil (%9,11). Unsaturated fatty acid composition is %55,51 to %90,19 for these oil varieties. Palmitic Acid (C16-0) is a major saturated fatty acid for all fats, followed by stearic acid (C18-0) for varieties other than olive oil. The major unsaturated fatty acid of sunflower and corn oil linoleic acid (C18-2) cis form, while palm olein and olive oil for oleic acid (C18-1) cis form. Fatty acid composition was found to affect the oil ratio of potato chips. A higher oil content was determined in the fried by unsaturated fatty acids. Foods fried with vegetable oils rich in single-polyunsaturated fatty acids absorb oil more. Based on the texture analysis results, stiffness values; corn oil 1,91 ±0,59 N, palm olein oil 1,7±0,42 N, olive oil 1,57±0,21 N and sunflower oil 1,48±0,33 N for the fracturability; corn oil 1,47±0,17 N, palm olein oil 1,36±0,31 N, olive oil 1,31±0,16 N and sunflower oil 1,1±0,1 N are calculated. The effect of different oil types on hardness analysis; olive oil, palm olein oil and sunflower oil were not different. It is also similar in corn and palm olein oil. Impact on fragility; except sunflower oil, other oils were statistically insignificant (p <0.05). On the other hand, except sunflower oil, other vegetable oils showed increase on diffusion coefficent in realation with the temperature. The diffusion coefficient, calculated by modeling, increases exponentially with increasing temperature for palm olein, olive and corn oil. The diffusion coefficient of sunflower oil is inversely proportional to increasing temperature. The diffusion coefficient values based on the exprerimental methods determined as; palm olein oil 1,35×10-7 m2/s, corn oil 1,28 ×10-7 m2/s, olive oil 1,2×10-7 m2/s and for sunflower oil 1,1×10-7 m2/s. On the other hand the model fluid system's diffusion coefficient values are founded as; corn oil 5,5×10-9 m2/s, palm olein oil 9,3×10-10 m2/s, olive oil 3,18 ×10-12 m2/s ve sunflower oil 14×10-14 m2/s. When the results were evaluated statistically, the two models used to determine the mass transfer of the oils showed a strong correlation with the textural properties of the chips. The saturated fatty acid composition of the oils and the hardness of the chips showed very poor correlation. However, the relationship between them was not statistically significant. In literature, there are studies which discuss about the mass transfer during the frying process of potato chips. But, there is no study which discuss the modelling of the potato composition and evaluating the diffusion ability of the vegetable oil with the help of dynamic light scattering technique. Therefore this study unique in this field. In order to accurately determine the diffusion coefficient of the oil in the model system, it is recommended to consider the deposition since more complex potato models are formed in the future, by re-examining the diffusion capability of the oil and gelatinizing the starch content at 60 ° C in the model structure. It is thought that these findings will help to improve frying mechanisms and improve the quality of potato chips.