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In recent years, the fascinating range of Response surface methodology (RSM) applications has captured the interest of many researchers and engineers worldwide. RSM is entirely based on well-known regression principles and variance analysis principles that enable the user to improve, develop and optimize the process or product under study. An overview of the theoretical principles of RSM, the experimental strategy and its tools and components, along with the applications and pros and cons, are described in this paper. Some of the widely used experimental designs of RSM compared in terms of its characteristics and efficiency are included, which helps to point out the importance of design of experiments (DOE) in optimization using RSM. The live demonstrations of a few optimization examples using response surface methodology in different research manuscripts included in this paper also provide a better understanding of the characteristics of RSM in different scenarios.

Background: Trans Fatty Acid (TFA) content in oil is an important quality parameter due to its adverse health effect. This study was aimed to examine the TFA content in the frying oil used by street food vendors in India for two traditional snack foods. Methods: Totally, 143 oil samples were collected at different frying times (0, 2, and 4 h) from five different vendors for Samosa and Jalebi. TFA levels of the oil samples were analyzed by Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATRFTIR). Statistical analyses were carried out using SPSS software version 23.0. Results: ATR-FTIR spectra exhibited an increase in peak intensity at 966 cm-1 with different frying time in both frying oil samples, indicating the formation of TFA. The TFA content in oils fried at 4 h was significantly higher than the ones at 0 and 2 intervals. It was found that 3 out of 74 (4%) Samosa fried oils and 12 out of 69 (17.4%) Jalebi fried oils were over the maximum allowed regulatory limit of TFA (5%). Jalebi fried oils had significantly higher TFA content than Samosa fried oils. Conclusion: The increase in frying time decreased the peroxide values and increased saturated fatty acids and TFA values of oils used for both food items. The local vendors and consumers should be educated by national authorities regarding health risk of TFA in street fried snacks.

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The bypass of an air bubble through a liquid−liquid interface may produce rich fluidic physics. Air injection is a passive technique to mix the contents of the two separated fluids and provides an effective heat and mass transfer intensification by increasing the interfacial area between them. Entrainment of heavier fluid into the lighter fluid at atmospheric and isothermal conditions has been simulated by using the VOF (volume of fluid) technique mimicking a Taylor bubble bypass through a horizontal liquid−liquid interface of water and polydimethylsiloxane (PDMS) solution. The migration of a Taylor bubble across the interface is completed through five different stages, namely, approach, encapsulation, de-encapsulation, entrainment, and detrainment. The bubble kinematics, entrained water volume, microdroplets formation, and film thinning characteristics have been studied in detail. The marginal pinch-off mechanism for the rupturing of the entrapped water film has been observed due to the presence of the surface tension gradient. The film thinning initially occurs due to the domination of gravitational force and eventually due to capillary force after the entrapped film thickness achieves capillary length scale, δ crit ∼ (σ/(ρg)) 1/2 . The entrapped water film shrinks over the interface of the Taylor bubble to generate the water microdroplets in the PDMS solution. The entrained height and volume of the water column grows quadratically with time.