Particulate foods, chemical markers

The chemometric principle was used to derive a guideline for obtaining a simple yes or no answer about the sterility of food particulates heated at aseptic processing temperatures. A quadratic temperature pulse model was used to estimate bacterial destruction from the fractional yield of thermally produced chemical marker compounds (2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one, M-1, and 4-hydroxy-5-methyl-3(2H)-furanone, M-2) and the rate constants and the activation energies of the chemical and bacterial systems. The model yielded a conservative estimate of lethality at the center of meat-balls heated under different time-temperature conditions. A scheme for determining the minimum marker yield for a designated F -value is provided. 

Several chemical marker compounds formed at sterilizing temperatures from precursor compounds inherently present in the foods have been reported (Kim and Taub, 1993 Kim et al, 1994). In order to apply these chemical markers to real processing conditions, where lethality accumulates under nonisothermal conditions, accurate informations about the reaction rate constants and their temperature dependence (activation energy or Z-value) are needed. The variability of the precursor concentration within the particulates and among different particulates also needs to be considered carefully. 

Kim, H.-J. Taub, I. A. Intrinsic chemical markers for aseptic processing of particulate foods. Food Technol. 1993, 47(1), 91-99. 

Principles and Applications of Chemical Markers of Sterility in H h-Temperature— Short-Time Processing of Particulate Foods... 

In either case, the time-temperature measurement within the moving food particulates is difficult, and consequently assuring commercial sterility without overprocessing is not a straightforward matter. In this p ier, we will discuss how thermally produced compoimds can be used as chemical markers of sterility in ohmic heating and microwave sterilization. 

The reported chemical markers are useful markers of sterility, which is an important quality index in shelf-stable foods. The use of the markers to map lethality distribution in particulate foods has been demonstrated. The markers can be used for validating and optimizing new thermal processing technologies such as ohmic heating and microwave sterilization. 

Chemical markers can mimic other processes. Chemical reactions taking place in foods can be used to mimic an entirely different process taking place in the vicinity of the site where the chemical measurements are made. An interesting example is the use of chemical markers to determine lethality within a food particulate where direct temperature measurement is not practical (Chapter 6). It appears that chemical reactions can mimic bacterial destruction, and are potentially useful time-temperature integrators in the continuous thermal processing of foods. 

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