Preparation of Sweet Potato Chips by Combined Method in Different Thicknesses

The objective of this research was to prepare sweet potato chips (Ipomoea batatas L.) in three different thicknesses (0.75, 1.25 and 1.75 mm) using a combined oven drying and frying process at three different temperatures (60, 70 and 80 °C) and to evaluate its centesimal composition, water content and texture (rupture resistance). The water and ash contents increased as the thickness increased and the opposite effect was observed for the lipids that reduced with increasing thickness. For the absorption of fat and calories, the chips presented varied values that can be attributed to the fact that the chips did not undergo the process of exhaustion after the frying. The highest values of rupture resistance (RR) were observed for the chips of 1.75 mm and the absorption of fat and water content interfered directly in this resistance. The sweet potato chips with lower caloric value were those that had drying at 60 °C in the thicknesses of 0.75 and 1.75 mm, however the best sample were chips with 0.75 mm thickness by the drying treatment at 60 °C combined with frying, taking into account the values of water content, calories and fracture.


Introduction
Sweet potato (Ipomoea batatas L.) is a tropical and subtropical plant which is also cultivated in temperate regions.Considered as one of the most popular tuberous crops in Brazil, much appreciated as food, being consumed in the form of baked or cooked and industrialized as sweet, and can be found with external colors, yellow, white and purple (Silva, Lopes, & Magalhães, 2010).It is a plant of great socioeconomic importance, participating in the supply of calories, vitamins and minerals in human food.The roots present carbohydrate content between 13.4 to 29.2% and reducing sugars of 4.8 to 7.8%.They are also excellent sources of carotenoids, potassium, iron and calcium (Embrapa, 2010).
Due to the excellent characteristics of sweet potato production, the perishability of this tuber and the lack of alternatives for industrialization have been pointed out as causes that restrict the expansion of this crop, causing a loss of capital.According to Grizotto (2010) the composition of sweet potatoes and their potential agricultural potential mean that this tuber can be used as raw material for various foods such as chips products, which have been occupying a growing space in the Brazilian market.However, one of the most important parameters in the quality of chips products is the amount of oil incorporated during the process, mainly because it is incompatible with the world trend of consumption of healthy products and low calorie and fat (Bouchon & Pyle, 2006).
One of the industrial processes that has proven efficient in obtaining food products is drying, being feasible in the processing of foods with high amounts of starch, such as tubers.Drying makes it possible to ensure the quality and stability of the products, considering that the decrease in the amount of water in the material reduces the biological activity and the chemical and physical changes that occur during storage (Resende, Corrêa, Goneli, Botelho, & Rodrigues, 2008).jas.ccsenet.
In this sce using a co and texture

Obtain
The flowc different th org enario, the obj mbined oven d es.

Note. Chip
The tubers immersed After remo and their t were imm 0.75 mm s After the b temperatur obtained ( packaging

Textur
The textur method pe the sample to the max the equatio where, RR = corresponds to rupture resistance (Pa); Fm = maximum force at the moment of chip rupture (N); A = cross-sectional area (m²).

Statistical Analysis
The results obtained in the centesimal composition were analyzed statistically to identify the best treatment for obtaining sweet potato chips.The data were interpreted through the analysis of variance and the averages of the treatments compared by applying the Tukey test.The program used was the Assistat 7.5 beta.(Silva & Azevedo, 2016) 3 Results and Discussion

Centesimal Composition and Water Activity
Analyzing Table 1, it can be observed that the values of water content and ash content of the chips increased as the thickness increased, a contrary effect is observed for the lipids which reduced with increasing thickness.
There was a statistically significant difference for the parameters of water content, water and protein activity with increasing treatment temperature.
According to the Brazilian Table of Food Composition ( 2006), the water content of potato chips, industrialized type chips is 2.37%.Table 1 shows that the lowest water content is 3.25%, observed in the sweet potato chips at the lowest thickness and pre-dehydrated at 80 °C.Also in Table 1 it is observed that for the water content of sweet potato chips of the same thickness dehydrated at different temperatures, there were significant differences in level of 5% of probability between the chips, being different water contents.Rogério, Leonel and Oliveira, (2005) (who studied the characterization of chips of tropical tuberoses (cassava, Arracacia xanthorrhiza, sweet potato, taro and yam), observed that in the processing of sweet potato, water loss during frying and water content of sweet potato chips reached 3.09%, an approximate value for the present study.
In relation to proteins, a variation of 1.26 to 1.85% is observed, Carvalho, Seccadio and Ferreira (2010) studying cassava chips obtained values of 0.97 to 1.06%, Oliveira (2009) analyzing different brands of fried potatoes chips, obtained values of proteins varying from 6.35 to 11.60%.Analyzing the values (Table 1), there were significant differences at a 5% probability level for all chips except for chips of 0.75 and 1.75 mm at 70 °C and 0.75 mm at 80 °C.Note.Means followed by the same letters in the column do not differ from each other by the Tukey test at 5% probability.DMS = significant difference.CV% = coefficient of variation in %.Rogério and Leonel (2004) studied sweet potato chips in the thicknesses of 1.5 and 2.0 mm under different pre-cooking conditions obtained values for lipids of 15.37 to 31.80% and observed that the pre-cooking did not interfere with the absorption of oil by the chips.According to the lipid contents of Table 1, it can be said that the drying pre-treatment is efficient with respect to the reduction of oil absorption for sweet potato chips.For the Figure Figure 2 o drying tempe

Table 1 .
Mean values of the centesimal composition and water activity of sweet potato chips