Microstructure of high-pressure vs. atmospheric frozen starch gels

Main Characteristics of Processed Grain Starch Products and Physicochemical Features of the Starches from Maize (Zea mays L.) with Different Genotypes

To understand the relationship between the genotype of maize plants and differences in their origin and the ploidy of the genome, which carry gene alleles programming the biosynthesis of various starch modifications, the thermodynamic and morphological features of starches from the grains of these plants have been studied. This study investigated the peculiarities of starch extracted from subspecies of maize (the dry matter mass (DM) fraction, starch content in grain DM, ash content in grain DM, and amylose content in starch) belonging to different genotypes within the framework of the program for the investigation of polymorphism of the world collection of plant genetic resources VIR. Among the starch genotypes of maize studied, four groups comprised the waxy (wx), conditionally high amylose ("ae"), sugar (su), and wild (WT) genotypes. Starches with an amylose content of over 30% conditionally belonged to the "ae" genotype. The starches of the su genotype had fewer starch granules than other investigated genotypes. An increase in amylose content in the investigated starches, accompanied by a decrease in their thermodynamic melting parameters, induced the accumulation of defective structures in the starches under study. The thermodynamic parameters evaluated for dissociation of the amylose-lipid complex were temperature (T_aml) and enthalpy (H_aml); for the su genotype, temperature and enthalpy values of dissociation of the amylose-lipid complex were higher than in the starches from the "ae" and WT genotypes. This study has shown that the amylose content in starch and the individual features of the maize genotype determine the thermodynamic melting parameters of the starches under study.

Facilitating high pressure phase-transition research and kinetics studies at subzero temperatures using self-cooling laboratory units

Self-cooling phase-transition units were built and tested to successfully carryout pressure shift freezing, high pressure thawing and subzero temperature microbial destruction kinetics. The design of these equipment has been progressively improved over the years as highlighted in this paper. Phase transition data on grape & apple juices, and sodium chloride (20%) & glucose solutions (20%) in Ice I were gathered and modeled using Simon-like and polynomial equations. Factors influencing the Ice I and water to Ice III phase transition position were evaluated, and found to be mainly affected by the solute in the aqueous solution. For pressure shifting freezing and pressure assisting freezing to Ice III, water and 20% sodium chloride solution were successfully employed and verified as cooling media for creating the temperature change pathway of potato and carrot. Using sodium chloride solution (20%) as the cooling medium, the phase transition pathway of apple juice and grape juice under high pressure for the phase transition of Ice I and metastable water to Ice III was established. This could be used in kinetic studies. The developed cooling unit concepts can use in any commercial high pressure equipment for subzero temperature treatment of foods without externally supplied cooling.