Magnetic resonance imaging (MRI) of a cookie in comparison with time-lapse photographic analysis (TLPA) during baking process.

Magnetic Resonance Imaging (MRI) has been used to study the baking of a cookie. The structural and dynamic changes occurring during baking have been monitored, including changes in the internal moisture saturations and distribution. The images reveal the moisture distribution is initially uniform, and during baking a gradient in moisture develops from the interior to the edge. Changes in physical dimensions calculated from the data are consistent with those obtained from time-lapsed photography.

NMR applications in complex food systems.

The rheological and functional properties of food components are related to their molecular structure, morphology, and atomic mobilities. NMR provides a powerful tool for elucidating chemical structures, molecular conformations, and interactions of components in food systems. Quantitative analysis of sugars, fats, and other principal compounds in complex food systems was achieved by high-resolution liquid NMR. In addition to information available from liquid experiments, solids NMR experiments can reveal differences and changes in crystal packing of structures in food model systems. Interpretation of experimental results is enhanced by molecular modeling of key food compounds. Models for fat crystallization are carried out to enhance understanding of the molecular structures involved in the fat crystallization process. Recently, MRI has also shown significant impact on food science and technology. Some examples of NMR applications are given in this presentation.

Effect of metal ion concentration on a biological reactor.

Saccharomyces cerevisiae (yeast) cells were employed as a source of alcohol dehydrogenase in the NAD(+)-to-NADH reaction. The cells were immobilized in calcium alginate monofilament fibers and used in a biological reactor. The alginate could not be heat sterilized since temperatures above 80 degrees C caused the polymer chains to degrade. The same proved true for the high pH necessary for the reaction, but the alginate strength was increased by Ba(2+) solution treatment. X-ray probe analysis showed that about 30% of the Ca(2+) sites exchanged with the Ba(2+) ions. The Ba(2+) ions (as well as the Ca(2+) ions) permeabilized the cells and increased the reaction rate. Long term trials showed that Ba(2+) ions were slowly elutriated from the fiber biocatalyst, causing a drop in reaction rate. The trend certainly was reversible as far as the fiber was concerned. It is assumed that the permeabilization of the cells by the Ba(2+) ions was a reversible process.

Mechanisms of heat damage in proteins. 7. The significance lysine-containing isopeptides and of lanthionine in heated proteins.

1. Studies have been made with solvent-extracted chicken muscle, bovine plasma albumin (BPA) and other proteins, all severely heated in the absence of carbohydrates so as to cause a large decrease in their fluorodinitrobenzene (FDNB)-reactive lysine contents. 2. epsilon-N-(beta-L-aspartyl)-L-lysine and epsilon-N-(gamma-L-glutamyl)-L-lysine isopeptides were determined after enzymic digestion of heated chicken muscle, and their content was found to increase as the material was subjected to more heat treatment. Heated chicken muscle was not found to contain lanthionine. Heated BPA, on the other hand, was found to contain lanthionine but not the isopeptides. Both lanthionine and isopeptide cross-linkages were detected in most of the other heated proteins. There was some difficulty in quantifying the amounts of isopeptides formed on heat treatment, because the enzymic digestion procedure used in their isolation appeared to be incomplete. Neither lysinoalanine nor ornithinoalanine was detected in any of the test materials.