Characterization of physical attributes of cassava chips in different frying conditions

Krepek tette is a variety of casava-based chips. However, the process production is quite different with cassava chips. After peeling, cassava is steamed, flattened, and dried. As one of the culinary signatures of Pamekasan, good quality keripek tette must be guaranteed by the Industry. Crispeness is the most essential factor in assessing the quality of this product. Therefore, this study aims to characterize product quality attributes such as moisture content, thickness expansion, porosity, and color products in different temperatures and frying times. The frying process used the deep frying method. The experiment was designed using two factors, and each experiment used three levels: temperature (150, 160, 170°C) and frying time (40, 50, 60 s). The result showed a higher temperature and frying time, and the moisture content of the product was lower. The thickness expansion increases in line with the temperature rising. However, it decreases with longer frying time. In addition, porosity increases linearly with temperature and frying time. The appearance of the product slightly changes. Before frying, the color of the product is yellowish, and after that, it turns slightly brownish. The result is the potential to develop an evaluation of crispiness quantitatively.


Introduction
Keripik tette is one of Madura's cuisines that is made of cassava, and it is a specialty product from Pamekasan.Moreover, there are three locations in which the favorite keripik tette is produced: Taro'an, Toronan, and Blumbungan village.Keripik tette differs from cassava chips because cassava is steamed, flattened, and dried after peeling.This process makes the product special because it can be mixed with other cuisines, namely Rujak, Campur, Soto, and Bakso.Typically, keripik tette is sold in raw products (dried chips form) in traditional markets or souvenir shops.This condition is an opportunity for the producer to elevate the product by serving a ready-to-eat product and providing a variety of snacks besides cassava chips.
One of the factors consumer acceptance benchmarks in chip purchases is crispness [1].Crispness is one of the parameters used to assess the texture of dry food products.According to the survey, crispness is the most essential factor in assessing the quality of chips [2].Crispness is when the volume of space in a material filled with water evaporates and is replaced with air caused by the frying or heating [2].This crispness is influenced by some factors, including pore diameter, thickness and pore wall hardness, development volume, and chip density [3].Moreover, crispness is influenced by moisture content and the composition of the ingredients [4].The crispness of the keripik tette can be noticed after the keripik tette is fried.This frying causes the development and formation of air cavities of chips in which the air cavities produce crispness of keripik tette [4].
Since the fried product of keripik tette is not yet available massively and to standardize the quality of fried products that meet consumer acceptance, the characterization of keripik tette through different frying temperatures and frying times is crucial to achieve a good product.Therefore, this study aims to characterise product quality attributes, namely, moisture content, puffiness, porosity, and color products in different frying temperatures and frying times.

Methods
This study was implemented in September -October 2023 and worked in the agroindustrial technology laboratory at the University of Trunojoyo Madura.This study was conducted with the deep frying method, which used an electric deep fryer model (Idealife, Japan).The deep fryer was controlled by an electric system, which maintained the frying temperature ± 5°C.This study applied two treatments: frying temperature (150°C, 160°C, 170°C) and frying time (40s, 50s, 60s).The observation parameters are moisture content, thickness, porosity, and color of products.The sample was kept in a zipper plastic bag after the temperature decreased to room temperature, approximately 1h after frying [5], and then the parameters were observed.The results of the data from the test were then analyzed using multiple linear regression and correlation methods.

Research parameters
2.1.1.Moisture content.The gravimetric method measured the fried keripik tette for moisture content.This test begins by ovening an empty cup for 30 minutes at 105°C, desiccator for 15 minutes, and then weighing the empty cup.The samples weighed 2g, placed in an empty cup, and weighed before drying.Oven empty cup and sample for 4 hours at 105°C and desiccator for 15 minutes, and then weigh empty cup and sample after drying.Next, re-oven the empty cup and sample for 1 hour at 105°C and desiccator for 15 minutes and then weigh the empty cup and sample after drying.The procedure is repeated until it reaches a constant weight.Moisture content was calculated using equation (1).
where: w = Initial sample weight (g) w1 = Weight of sample and empty cup after drying (g) w2 = Empty cup weight (g) 2.1.2.Thickness expansion.The percentage thickness expansion was measured using a caliper.Measurement was made on 3 samples for each treatment, and each sample was measured in 20-point observation.The formula to calculate the percentage of thickness expansion (  ) correspond to equation (2) [6].
where:   = thickness before frying (mm) () = thickness after frying (mm) 2.1.3.Porosity.The measurement of the solid density used a pycnometer.The step begins with grinding 2 g of sample, then dissolved with 30 ml of aquadest.After that, a reconstituted sample was filtered using a filter cloth to separate the keripik tette powder from the mixture.Next, two empty pycnometers were heated in the oven for 10 minutes and stored in a desiccator for 10 minutes.After that, the first empty pycnometer was weighed, filled with aquadest to the maximal volume, and weighed again.Later, the second empty pycnometer was weighed, filled with samples to the maximal volume, and weighed again.The sample was measured in triplicate.Solid density was calculated through equations ( 3): Meanwhile, the calculation of bulk density used the principle of liquid displacement.However, in this study, liquid was replaced with green bean seeds.The sample was measured in triplicate.The solid and bulk density value was used to calculate the porosity for each treatment.Porosity was calculated using equation ( 4) [5].

Statistical analysis
Data analysis performed in this study includes independent variables (temperature and frying time) and dependent variables (moisture content, thickness expansion, porosity).The result of the data from the test was then analyzed using a multiple linear regression method.Data is formulated using Excel.Moreover, regression analysis is used to generate a response function and fitted to a first polynomial (7) or second-degree polynomial (8) [5].The function was evaluated based on p-value, where if the p-value > 0.05, then there is a significant effect on the parameters of keripik tette; otherwise, if the p-value < 0.05, then there is no significant effect on the parameters of keripik tette.A stepwise backward regression was applied to experiment data to obtain coefficients of the polynomial function.
Correlation analysis was carried out to determine the closeness of the relationship between moisture content, thickness expansion, solid density, bulk density, and porosity.The two variables' correlation coefficient (r) is 0 and ±1.If two variables have a value r = 0, there is no relationship between the variables.Otherwise, if two variables have a value r = ±1, two have a perfect relationship [8].Minus sign (-) indicates an opposite relationship, meaning if the value of one variable increases, the value of another variable decreases, while plus sign (+) indicates a unidirectional relationship, meaning if the value of one variable increases, the value of other variables also increases [8].

Physical properties of keripik tette
The moisture content response plot (Figure 1a) shows the highest moisture content of keripik tette in the frying with a temperature of 150°C for the 40s, which was 5,759% (w.b).The lowest moisture content of keripik tette in the frying with a temperature of 170°C for the 60s is 2,577% (w.b).The results revealed that moisture content decreased along with high frying temperature and length of frying time.The same result was also obtained by Saeleaw and Schleining [5], which resulted in lower moisture content.While research on keripik tette products has never been done.Regression analysis supported this result that frying temperature and time had a significant effect (p<0.05).Higher temperatures ignite more heat during frying, and more water evaporates.As a result, water contained in the chips decreases [9].Another factor that made water evaporate effectively was the product's dimension because the product's dimension also contributed to the decrease of moisture content and vice versa [10].Meanwhile, the average thickness of the keripik tette ranged from 0.7 mm to 1.9 mm.
Figure 1b shows the thickness expansion of the keripik tette.The highest thickness expansion in frying temperature at 170°C for the 40s was 190.6%.Meanwhile, the lowest thickness expansion in frying at the temperature of 150°C for the 50s was 27.7%.The thickness expansion is linearly increased with higher temperature; meanwhile, frying time showed more effectiveness quickly.The same result was also obtained by Saeleaw and Schleining [5], which resulted in a high percentage of linear expansion at 160°C for 10s during the frying of cassava crackers.This observation was also related to statistical analysis that frying temperature and frying time had a significant effect (p<0.05) on the thickness expansion of the keripik tette.This condition happens because longer and higher temperatures are used, resulting in pores in the chips so that the puffiness increases [6].
The porosity shown in Figure 1c indicated the highest porosity in the frying temperature at 160°C for the 60s, which is 0,906291.Meanwhile, the lowest porosity in the frying temperature at 150°C for the 40s is 0,814803.The results show that frying temperature and time had a significant effect (p<0.05) on the porosity of keripik tette.This phenomenon happens when the water evaporates, making the pores in the chips' structure.High porosity is associated with water loss during the frying process [11], in which water loss is directly related to oil absorption.As a result, the oil can uptake the part of the void space left by water vapor during evaporation, especially during cooling conditions [12].As for multiple linear regression modelling is in Table 1.

Color
Figure 2 shows value of parameters for each treatment.Meanwhile, Figure 3 shows that the appearance of keripik tette is in accordance with the color parameter data generated.The product visual was compared based on color analysis, namely, Total difference color (), and Yellowness index (YI).The  value indicates the darker color of a material [13].The highest  value was produced by 160°C, 60s at 19.7786, while the lowest  value was produced by 160°C, 50s treatment at 12.8349.The highest  value indicates that the keripik tette's color is striking.In contrast, the lowest  value indicates that the keripik tette's color is fading [13].The average  produced from all treatments is small because the color produced in keripik tette is fading or not yellow.
The YI value before frying with the highest value is 160°C, 40s of 163, while the lowest value is 160°C, 50s of 125.YI value after frying with the highest value is 150°C, 40s of 112, while the lowest value is 170°C, 50s of 71.If the YI value is more than 138, the resulting color is bright yellow or striking; otherwise, if the YI value is less than 138, the resulting color is slightly brownish.After the frying process, the YI value decreased due to the frying process, which caused the brownish color of keripik tette to be produced.The brownish color of chips is caused by the Maillard (browning non-enzymatic) [14].The benefit of knowing the YI value for chip products is related to the appearance of chips after frying [15], and the appearance of the chips is one of the attractions of buying a chip product.

Statistical analysis
Regression analysis results are described in Table 1.Regression analysis shows that the moisture content is included in the first-order polynomial.The thickness expansion is included in the second-order polynomial, and the porosity is included in the second-order polynomial.The R 2 is used to measure the ability of the model to explain variations in the independent variable [16].The R 2 value is 0.96979, which indicates that the temperature and time of frying affect the moisture content by 96.97%, while other factors outside this study influence the remaining 3.03%.The R 2 value is 0.8805, which indicates that the temperature and time of frying affect the thickness expansion by 88.05%, while other factors outside this study influence the remaining 11.95%.The R 2 value is 0.9576, which indicates that the temperature and time of frying affect the porosity by 95.76%, while other factors outside this study influence the remaining 4.24%.The F test determines the significance of the relationship between variable X and variable Y and whether variable X affects variable Y [16].The sign-F value generated by the parameters of moisture content, thickness expansion, and porosity shows that all of them are < alpha 0.05, so it can be concluded that there is a significant influence between variable X and variable Y.  2. Correlation analysis shows that the correlation coefficient between the bulk density and porosity variables is the strongest negative correlation, which means that the higher the bulk density value, the lower the porosity value.The correlation coefficient between moisture content and bulk density variables is the strongest positive correlation, which means that the higher the moisture content value, the higher the bulk density value is.A higher correlation coefficient between two variables or closer to 1 means a stronger relationship between two variables.Meanwhile, if the lower correlation coefficient between two variables is closer to 0, it means a weaker relationship between two variables [8].

Conclusion
Based on the study, it can be concluded that the effect of temperature and frying time on characteristics of keripik tette product is higher temperature and longer frying time, then the lower moisture content which is 2,577% (w.b)., increased puffiness which is 190.6%, and higher porosity which is 0,906291.The color produced for all treatments is generally brownish.

Figure 1 .
Figure1.Physical properties of keripik tette in the three-dimensional graph as a response to different frying temperatures and times.As for multiple linear regression modelling is in Table1.

( a )Figure 2 .Figure 3 .
Figure 2. Color parameters with different frying temperature and frying time

Table 1 .
Regression analysis for physical atribute of keripik tette.