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Effect of High Pressure CO2 Treatment on the Moisture Sorption Isotherm and Physicochemical Properties of Beef Jerky
- Author / Creator
- Ren, Yanzhao
High pressure carbon dioxide (HPCD) treatment is a promising non-thermal pasteurization technique, targeting the enhancement of food safety by inactivating microorganisms without sacrificing quality. Even though this technique is effective for high moisture foods, research on products with a low water activity (aw) is limited. Beef jerky, as a low aw ready-to-eat snack, has become more popular because of the growing trend of high-protein and low-carb diets. The objective of this thesis research was to investigate the effects of HPCD treatment on the moisture sorption behavior and physicochemical properties of beef jerky.
Moisture sorption isotherms (MSIs), monolayer water content (M0) and net isosteric heat of sorption (qst) were determined under air and CO2 environments at ambient pressure, as well as HPCD environment. MSI data were described mathematically by fitting into six isotherm equations. The deviation of the models used to fit the data increased under CO2 atmosphere at ambient pressure and HPCD conditions. At ambient pressure, compared to the air environment, samples in CO2 environment had higher aw at a given moisture content. Under HPCD environment, the shape of MSIs changed from type II to type III and the isotherms became very steep at aw levels of 0.73 and 0.70 at high pressures of 57 and 200 bar, respectively. Monolayer water content decreased with temperature, but pressure did not have a significant effect on M0. Net isosteric heat of sorption in CO2 environment was higher than that in air environment and the differential between the two environments decreased when the moisture content was increased.
The effects of HPCD processing parameters, including pressure, temperature, processing time and depressurization rate, on the physicochemical properties, including, aw, surface color, fat content, and Warner-Bratzler shear force, of beef jerky were studied by response surface methodology (RSM). Water activity decreased after HPCD treatment and temperature had a significant effect. In terms of surface color profile, L, a, b values increased after HPCD treatment and pressure had a significant effect on L value, no processing parameter showed a significant effect on a value, and pressure, quadratic pressure and depressurization rate had a significant effect on b value. After HPCD treatment, fat content of beef jerky was reduced slightly but no processing parameter had a significant effect. Warner-Bratzler shear force was either increased or decreased after HPCD treatment, where quadratic depressurization rate and linear temperature had a significant effect. An optimum HPCD treatment condition, that is, pressure of 92.9 bar, temperature of 59.1˚C, processing time of 35.9 min and depressurization rate of 56.3 bar/min, was determined via the RSM model to minimize the changes in responses.
The results obtained from this thesis research provide valuable information on further understanding of moisture sorption behavior during HPCD treatment that would contribute to elucidation of the microbial inactivation mechanism and the impact of HPCD treatment on the quality attributes of a low aw food product like beef jerky.
- Graduation date
- Fall 2019
- Type of Item
- Master of Science
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