Development of a novel methodology to validate optimal sterilization conditions for maximizing the texture quality of white beans in glass jars

Optimal thermal processes were designed for white beans in glass jars heated in a still and end-over-end rotary pilot water cascading retort. For this purpose, isothermal kinetics of thermal softening of white beans were studied in detail using a tenderometer and a texturometer. The fractional conversion model was applied in both cases to model the texture degradation. The Arrhenius equation described well the temperature dependence of the reaction rate constant. With regard to the heat transfer, heat penetration parameters (fh and jh) were experimentally determined from 100 containers under static as well as rotational (end-over-end) conditions at 4, 7, 10, and 15 rpm. Theoretical optimal temperatures, maximizing volume average quality retention, were calculated using a computer program valid for conduction heating foods. Experimental verification of the calculated results was conducted. Considering the finite surface heat transfer coefficient, theoretical and experimental optimal temperatures were of the same order of magnitude, around 130 °C, while for an infinite surface heat transfer coefficient the calculated optimum temperature was much lower than the experimental value. The type of reaction kinetic model, fractional conversion or first-order models, does not significantly affect optimal sterilization temperatures. Although some differences were found, the developed theoretical approach was successfully applied to convective and mixed heating mode products. The use of the correct surface heat transfer coefficient is crucial to design optimal processing conditions.