Physico-chemical changes of fried products during oil and vacuum frying

Abstract

With critical analysis of the available literature, this review article emphasizes upon physico-chemical changes of various fried food products during oil and vacuum frying processes. Physical characteristics involve texture and colour. On the other hand, chemical and nutritional parameters include moisture content, fat content, acrylamide, carotenoids, flavonoids, phenolics etc. Such investigation affirmed positive dependency of textural parameters such as hardness, firmness and stiffness with temperature and time during both oil and vacuum frying processes. Similarly, colour such as L*, a*, b* and ΔE enhances during the frying processes. On the other hand, nutritional parameters such as protein, fat, carotenoids, flavonoids and phenols reduced significantly with increase in temperature and time during oil and vacuum frying. On the other hand, such frying processes leads to a toxic compound known as acrylamide which is carcinogenic in nature. Thus, this article addresses the major parametric changes during oil and vacuum frying processes. This would facilitate product-process design for the said frying processes. Further, it would be beneficial to design a frying equipment and optimize the process condition. The main result of this study was the demonstration by Sothornvit R. that the use of two hydrocolloids (guar gum and xanthan gum) helped reduce the oil absorption of vacuum-fried banana chips, giving values of 8-9% oil absorption, hardness 27.32 N (Sothornvit R, 2011). Variation of Gulab Jamun balls with temperature.-130oC and time-10 minutes, activation energy, texture-24.5-77.6 kJ/mol, color-28.66-43.52 kJ/mol, lightness (L*)-79.86 decreased to 23.48-29.25, overall color (ΔE)-53.22-59.30, hardness-0.168 N/mm-3.935 N/mm, strength-0.13 N/mm-11.19 N/mm, stiffness-0.19N/mm2-7.91N/mm2. This paper aims to study the combined effect of different baking methods on fruits and vegetables and some traditional sweets.