Philippine Journal of Science
150 (1): 43-52, February 2021
ISSN 0031 – 7683
Date Received: 08 Jun 2020

Moisture Sorption Characteristics and Isosteric
Heat of Sorption of Vacuum Fried Chicken
(Gallus gallus domesticus L.) “Isaw”

Anastacio T. Cagabhion III¹* and Ivy C. Emnace²

¹Department of Home Economics
College of Agriculture, Forestry and Environmental Sciences
Western Philippines University, San Juan, Aborlan, Palawan 5302 Philippines

²Department of Food Science and Technology
College of Agriculture and Food Science
Visayas State University, Visca, Baybay City, Leyte 6521 Philippines

*Corresponding author: nashjayahr@gmail.com

ABSTRACT

Chicken “isaw,” which is common street food in the Philippines, is prepared by conventional frying and is observed to have poor shelf-life and keeping qualities. Hence, a new product was developed employing vacuum frying technology to minimize undesirable changes and provide longer shelf-life as the conditions under vacuum frying involves the use of low temperature and minimal exposure to oxygen. However, data on its quality is not yet available since the product is new. Thus, the development of sorption isotherm and understanding of isosteric heat of sorption to the newly developed product is essential for the quantitative approach to predicting stability and quality changes during packaging and storage. Isotherms of vacuum fried chicken “isaw” were measured at 20 °C, 30 °C, and 40 °C by the static gravimetric method over a range of relative humidity (RH) from 7–75%. BET (up to 43% Aw), Smith, Kuhn, Oswin, Karel, and Peleg were the mathematical models used in fitting the experimental sorption data. Corresponding to BET, the monolayer moisture content (Xm) revealed that the vacuum fried chicken “isaw” must have a moisture content of 3.79%, 1.98%, and 1.96% at 20 °C, 30 °C, and 40 °C, respectively to prevent auto-oxidation and to enhance product stability of vacuum fried chicken “isaw” during storage. The net isosteric heat was calculated using the Clausius-Clapeyron equation and was observed that as moisture content is decreased, the isosteric heat of sorption increases. With these data gathered, generating and understanding the product’s sorption isotherm, energy constants, and general equation at 20 °C, 30 °C, and 40 °C would provide valuable information for predicting quality changes during storage and packaging and for convenience in its future processing in an attempt to improve its quality, safety, and profitability.