Optimization of Process Parameters for Producing RTE Puffed Groundnut (Kharmure)

Introduction

The Ready-To-Eat (RTE) food sector represents a significant component of the food industry. The importance of RTE puffed and popped snacks are an undeniable fact in the era of fast life, rapid urbanization convenience and all a health-conscious society. RTE snacks prepared by puffing and popping of cereals, pulses and millets may provide a myriad of choices for meeting today's

Materials and Methods Preparation of puffed groundnut

The groundnuts are procured from local market of Parbhani. The raw groundnuts were soaked for 45 min, and then soaked groundnut were surface dried for 4 h prior to puffing. Groundnuts were puffed using a multigrain puffing-cumpopping machine at 250 o C and 3 RPM, developed by the Department of Agricultural Process Engineering, College of Agricultural Engineering and Technology, VNMKV, Parbhani. The High Temperature Short Time (HTST) principle is the basis for its operation. A consistent grain to salt ratio of 1:10 is essential for effective puffing. The machine is equipped with a rotating drum and a panel that digitally controls the temperature.

Quality Evaluation of Puffed Groundnut Within the Experimental range

Puffing yield:The puffing yield of puffed groundnut is a ratio of final number of puffed grains to the number of total grains of puffed groundnut Puffing yield was calculated by using following formula 𝑃𝑢𝑓𝑓𝑖𝑛𝑔 𝑌𝑖𝑒𝑙𝑑 = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑃𝑢𝑓𝑓𝑒𝑑 𝑔𝑟𝑎𝑖𝑛𝑠 𝑇𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑔𝑟𝑎𝑖𝑛𝑠 ∈ 𝑠𝑎𝑚𝑝𝑙𝑒 × 100

Expansion Ratio:

The expansion ratio was determined by measuring the average bulk volume of the product post-puffing and comparing it to its original average bulk volume. (Jadhav et al., 2018) [7] 𝐸𝑥𝑝𝑎𝑛𝑠𝑖𝑜𝑛 𝑟𝑎𝑡𝑖𝑜 = 𝑇𝑜𝑡𝑎𝑙 𝑝𝑜𝑝𝑝𝑒𝑑 / 𝑝𝑢𝑓𝑓𝑒𝑑 𝑣𝑜𝑙𝑢𝑚𝑒(𝑐𝑚 3 ) 𝑣𝑜𝑢𝑙𝑚𝑒 𝑜𝑓 𝑟𝑎𝑤 𝑘𝑒𝑟𝑛𝑙𝑎𝑠(𝑐𝑚 3 )

Color:

The L-value, indicating the color of the puffed groundnuts, was measured using a Hunter Lab colorimeter. These color readings are reported as L-values. Measurements were taken two days following the popping experiment (Jadhav, 2018) [7] . The Lvalue quantifies the lightness on a scale from 0 (black) to 100 (white). It was noted that the 'a' and 'b' values showed minimal variation with different process parameters, so the focus of this study was solely on the L-value (lightness). For each experimental sample, the average of three replicates was calculated (Tavanandi et al., 2021) [8] .

Textural Properties: Textural properties of puffed groundnut, specifically hardness and crispness, were assessed using a Stable Micro System TA-XT plus texture analyser from Texture Technologies Corp., UK. The analysis employed a cylindrical probe P75 with a testing force of 0.05N, 50% strain, measuring force in compression mode, a pre-test speed of 0.5 mm/s, and a test speed of 1 mm/s. Hardness was quantified using the average peak compression force, while crispness was determined from the major positive peaks obtained during compression. (Jaybhaye and Srivastav, 2015 and Anon et al., 1998) [9,10] . Each experiment involved averaging 10 replications for both parameters.

Effects of Process Parameters on the Quality Attributes of Puffed Groundnut Design-Expert software (Version 10.0, Stat-Ease Inc., Minneapolis, MN, USA) was employed to create response surface graphs and contour plots, these graphs and contour plots are used to assess how process variables influenced the response variables (Jaybhaye and Srivastav, 2015) [9] . The same software facilitated both numerical and graphical optimization of the process parameters, aiming to decide the optimal levels of the independent variables. This optimization sought to enhance popping efficiency and expansion ratio while ensuring the desired bulk density, hardness, color, and crispiness were achieved (Montgomery, 2001; Pawar et al., 2014) [11] . The experimental setup was crafted following the selection of parameter ranges, utilizing the Box Behnken Design (BBD) with three variables, each having three levels. Where, y represents predicted response, Xi and Xj represents independent variables, β0= regression coefficients for interept, βi= linear coefficient, βii= squared coefficient, βij= interaction coefficient, ε =noise or error.

Results and Discussion

Impact of Different Process Parameters on Puffing Yield Table 2 displays the calculated puffing yield values for puffed groundnut produced using various combinations of process parameters. The puffing yield values for puffed groundnut were found to range from 56.74% to 97.63% across the different variable combinations examined. The quadratic equation that illustrates the impact of process parameters on the puffing yield of puffed groundnut, expressed in terms of the actual levels of variables, is provided as follows:

Where, X 1 = soaking time, X 2 = surface drying time and X 3 = puffing temperature

The effects of the processing variables on the puffing yield of groundnut were evaluated using the ANOVA F-values (Table 3) and the estimated regression coefficients of the actual variables. The developed quadratic model was highly significant (Model F-value=386.77; p <0.05) , indicating that it adequately explained the variation in puffing yield. In addition, the lack-of-fit was non-significant, confirming the suitability and predictive capability of the fitted model within the experimental domain. The positive linear regression coefficients for soaking time (X₁) , surface drying time (X₂) , and puffing temperature (X₃) indicated that increasing these process variables enhanced the puffing yield over the investigated range. As illustrated in Figure 1, the puffing yield increased progressively with increasing soaking time up to 45 min, surface drying time up to 4 h, and puffing temperature up to 250 °C . These findings suggest that adequate hydration, controlled moisture removal, and higher puffing temperature collectively promoted efficient expansion of the groundnut kernels, resulting in improved puffing yield.

Impact of Different Process Parameters on Expansion ratio (ER)

Table 2 displays the calculated expansion ratios for puffed groundnut, which were prepared using various combinations of process parameters. The expansion ratios observed for the puffed groundnut varied from 1.11 to 1.31 across the different variable combinations examined. The quadratic equation that illustrates how the process parameters influence the expansion ratio of puffed groundnut, based on the actual levels of the variables, is provided as follows:

Where, X 1 = soaking time, X 2 = surface drying time and X 3 = puffing temperature

The influence of the processing variables on the expansion ratio of puffed groundnut was evaluated using the ANOVA F-values and the regression coefficients of the actual variables (Table 3).

The developed response surface model was statistically significant (Model F-value=14.81; p<0.05) indicating that the selected variables adequately explained the variation in expansion ratio. The positive linear coefficients of soaking time (X₁) , surface drying time (X₂) , and puffing temperature (X₃) demonstrated that increasing these processing parameters enhanced the expansion ratio within the experimental range. However, the negative quadratic coefficients indicated that further increases beyond the optimum levels resulted in a decline in expansion ratio, reflecting the existence of curvature in the response surface. Among the investigated variables, puffing temperature (X₃) had the most pronounced effect on the expansion ratio, followed by soaking time (X₁) and surface drying time (X₂) . As illustrated in Fig. 2, the expansion ratio increased with soaking time up to 45 min, surface drying time up to 4 h, and puffing temperature up to 250 °C . Beyond these optimum conditions, a progressive decline in expansion ratio was observed, which may be attributed to over-processing and structural deterioration of the groundnut kernels, thereby limiting further expansion during puffing. 6.02 NS PY-puffing yield, ER-expansion ratio, CRP-crispiness, HDS-hardness, L-colour value -significant, and NS-Non-significant Table 2 displays the calculated crispiness values for puffed groundnuts produced using various combinations of process parameters. The crispiness values of the puffed groundnuts were found to vary between 13 and 23 (number of positive peaks) across the different variable combinations examined. The quadratic equation that illustrates how the process parameters influence the crispiness of puffed groundnuts, based on the actual levels of the variables, is provided as follows:

Where, X 1 = soaking time, X 2 = surface drying time and X 3 = puffing temperature The effect of the processing variables on the crispiness of puffed groundnut was evaluated using the ANOVA F-values and the regression coefficients of the coded variables (Table 3). The developed model was statistically significant, with a Model Fvalue of 24.89 (p<0.05) , indicating that the selected variables adequately explained the variation in crispiness. The positive linear coefficients of surface drying time (X₂) and puffing temperature (X₃) indicated that increasing these process variables enhanced the crispiness of the product within the experimental range. In contrast, the negative interaction and quadratic coefficients suggested that excessive levels of these variables adversely affected crispiness, reflecting the presence of an optimum processing region. As illustrated in Fig. 3, the crispiness of puffed groundnut increased with soaking time (X₁) up to 45 min, surface drying time (X₂) up to 4 h, and puffing temperature (X₃) up to 250 °C . Beyond these optimum conditions, particularly with further increases in surface drying time and puffing temperature, the crispiness decreased, which may be attributed to excessive moisture loss and structural changes in the puffed kernels that reduced the desirable crisp texture.

Impact of Different Process Parameters on Hardness

The hardness of puffed groundnuts was assessed using the TA. XT-2 Texture Analyser, following the experimental design outlined in Table 2, for various process parameter combinations. The hardness ranged from 49 to 140 N across the studied variable combinations. The quadratic equation that illustrates how the process parameters influence the hardness of puffed groundnuts, based on the actual levels of the variables, is provided as follows:

Where, X 1 = soaking time, X 2 = Surface drying time and X 3 = puffing temperature The effect of the processing variables on the hardness of puffed groundnut was evaluated using the ANOVA F-values and the regression coefficients of the coded variables (Table 3). The developed response surface model was highly significant, with a Model F-value of 192.58 (p<0.05) , indicating that the model adequately explained the variation in hardness. The negative linear regression coefficients of soaking time (X₁) , surface drying time (X₂) . , and puffing temperature (X₃) indicated that increasing these processing variables reduced the hardness of puffed groundnut within the experimental range. Among the investigated factors, puffing temperature (X₃) exerted the greatest influence on hardness, followed by soaking time (X₁) and surface drying time (X₂) As illustrated in Fig. 4, the hardness of puffed groundnut decreased with increasing soaking time up to 45 min, surface drying time up to h, and puffing temperature up to 250 °C . The reduction in hardness under these processing conditions may be attributed to enhanced moisture distribution during soaking, controlled moisture removal during surface drying, and greater expansion of the kernels at higher puffing temperatures, resulting in the formation of a porous structure with a softer texture.

Impact of Different Process Parameters on color (L-value) of puffed groundnut

The lightness of puffed groundnut, influenced by different process parameters, was measured using a Colour Flex Hunter Lab Colorimeter, represented by the (L-value). This value reflects the brightness of the puffed groundnut. It was found that the L-value of the puffed groundnut varied between 32.73 and 50.85 (Table 2) across the studied variable combinations. The quadratic equation that illustrates how the process parameters affect the L * ₋ value of puffed groundnut, based on the actual levels of the variables, is provided as follows: Where, X 1 = soaking time, X 1 = surface drying time and X 1 = puffing temperature The influence of each factor on color (L-value) can be assessed through the F-values from the analysis of variance (Table 3) and the size of the coefficients of the coded variables. The ANOVA results indicate a model with an F value of 15.93 at a 5% significance level. The lack of fit F value is not significant, indicating a good model fit. Positive coefficients for linear terms suggest that an increase in these parameters leads to a rise in the color L-value of puffed groundnut. Conversely, negative coefficients for the quadratic terms imply that an excessive increase in these parameters causes a reduction in the color L*value of puffed groundnut.

Optimization

Design-Expert software (Version 10.0, Stat-Ease Inc., Minneapolis, MN, USA) was employed to optimize multiple responses simultaneously. The software provided optimal conditions for independent variables along with predicted response values. The ideal values for process variables were determined through graphical optimization as follows:

Conclusion

The design of experiments and optimization employed the BBD and RSM techniques, which effectively demonstrated how process parameters (ST, SD, and PT) influenced the responses (PY, ER, HD, CSP, and L * . -value) of puffed groundnut. The ideal puffing conditions for groundnut grains involved heating to 250 °C , , followed by a soaking period of 45 minutes and a surface drying duration of 4 hours. Under these optimal conditions, the puffed groundnut achieved a puffing yield of 97.63%, an expansion ratio of 1.29, crispness with 22 positive peaks, hardness of 69 N, and a color L*-value of 50.23.

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