High-temperature Short-time Conditions Research Articles

The impact of thermal processing on the simulated infant gastrointestinal digestion, bactericidal and anti-inflammatory activity of bovine lactoferrin – An in vitro study

Lactoferrin (LF) is a multifunctional glycoprotein which, when thermally processed, undergoes significant physicochemical changes. The link between such changes and the bioactivity of LF is not well characterised and requires much research. In this work, bovine LF solutions (1%, w/v, protein, pH 7) were thermally processed using high temperature short time conditions (72, 80, 85 or 95 °C with 15 s holding times). Following this, it was shown that LF and heat induced LF aggregates were largely resistant to simulated infant gastric, but not intestinal, digestion. Also, the efficacy of LF bactericidal activity, and inhibition of lipopolysaccharide-induced NF-κB activation were negatively impacted by thermal processing. This study confirmed that the efficacy of LF bio-functionalities was affected by the extent of heat-induced changes in protein structure whereby processing conditions of least severity (i.e. pasteurisation) had the least impact on bioactivity.

Ascorbic acid degradation kinetics in mushrooms in a high-temperature short-time process controlled by a thermoresistometer

The degradation of ascorbic acid was studied in mushrooms heated at temperatures between 110 and 140°C, high-temperature short-time conditions, in a five-channel computer-controlled thermoresistometer. The kinetics parameters were calculated on the assumption that there are 2 degradation mechanisms, one aerobic (during the first few seconds of the process) and the other anaerobic. The 2 stages followed first-order reaction kinetics, with E a=46.36 kJ/mol for aerobic degradation and E a=49.57 kJ/mol for anaerobic degradation.

Microbial inactivation of paprika by a high-temperature short-X time treatment. Influence on color properties.

High-temperature short-time (HTST) treatments have been used to destroy the bioburden of paprika. With this in mind, we have designed a device to treat samples of paprika with a gas whose temperature, pressure, and composition can be selected. Temperatures and treatment times ranged from 130 to 170 degrees C and 4 to 6 s, respectively. The survival of the most commonly found microorganisms in paprika and any alteration in extractable and superficial color were examined. Data showed that the optimum HTST conditions were 145 degrees C, 1.5 kg/cm2 of overpressure, 6 s operation time, and a thermal fluid of saturated steam. No microbial growth was detected during storage after thermal treatment. To minimize the color losses, treated (HTST) paprika samples should be kept under refrigeration.

Thermal sterilization of heat‐sensitive products using high‐temperature short‐time sterilization

High‐temperature short‐time (HTST) sterilization with a continuous‐flow sterilizer, developed for this study, was evaluated. The evaluation was performed with respect to (a) the chemical degradation of two heat‐sensitive drugs in HTST range (140–160°C) and (b) the microbiological effect of HTST sterilization. Degradation kinetics of two heat‐sensitive drugs showed that a high peak temperature sterilization process resulted in less chemical degradation for the same microbiological effect than a low peak temperature process. Both drugs investigated could be sterilized with acceptable degradation at HTST conditions. For the evaluation of the microbiological effect, Bacillus stearothermophilus ATCC 7953 spores were used as indicator bacteria. Indicator spore kinetics (DT, z value, k, and Ea), were determined in the HTST range. A comparison between the Bigelow model (z value concept) and the Arrhenius model, used to describe the temperature coefficient of the microbial inactivation, demonstrated that the Bigelow model is more accurate in prediction of DT values in the HTST range. The temperature coefficient decreased with increasing temperature. The influence of Ca2+ ions and pH value on the heat resistance of the indicator spores, which is known under typical sterilization conditions, did not change under HTST conditions. © 2001 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:275–287, 2001

Processing conditions influencing the physical properties of French fried potatoes

Achieving optimal colour and texture in French fries requires careful control of the unit operations that convert the raw potatoes into fries. The effects of variation in blanching, drying and finish frying conditions on puncture properties (peak force and peak deformation) and Hunterlab L (lightness) values of French fries were investigated. Fries blanched by low-temperature long-time (LTLT) conditions had larger peak force, peak deformation and L value than fries processed by standard conditions. High-temperature short-time (HTST) blanching increased lightness but decreased peak force and peak deformation. For drying, the colour and textural quality of French fries processed by standard conditions were better than those processed by the drying alternatives. For finish frying, LTLT conditions increased peak force whereas HTST conditions increased lightness. Therefore, a compromise has to be made in processing conditions to optimise both colour and textural quality. Even after finish frying, compositional differences within potato tubers influenced texture, both between and within French fries.

Kinetics of green asparagus ascorbic acid heated in a high-temperature thermoresistometer

Thermal degradation of green asparagus ascorbic acid in high-temperature short-time conditions was studied by heating in a five-channel computer-controlled thermoresistometer. Ascorbic acid was heated to between 110 °C and 140 °C and the degradation kinetics were analyzed assuming that two different inactivation mechanisms were occurring, one aerobic and the other anaerobic. The two reactions followed first-order kinetics, with E a=12.3(2.0) kcal/mol and k 125 °C=47.0(3.0)×10–3 s–1 for the aerobic oxidation, and E a=6.1(1.4) kcal/mol and k 125 °C=4.1(0.2)×10–3 s–1 for the anaerobic degradation.

High-Temperature Short-Time Inactivation of Peroxidase by Direct Heating with a Five-Channel Computer-Controlled Thermoresistometer

The thermal inactivation kinetics of horseradish and asparagus peroxidase in high-temperature short-time conditions was studied by heating in a five-channel computer-controlled thermoresistometer. Horseradish peroxidase was heated between 111.5 and 145°C and the reaction was analyzed assuming that two isoenzymes with EaL = 44.1 and Eas = 22.0 kcal/mol were present. Asparagus peroxidase heated from 110 to l20°C reacted with first-order kinetics, with Ea = 20 kcal/mol. The five-channel computer-controlled thermoresistometer enabled us to study the inactivation kinetics of the more labile fraction of horseradish peroxidase at temperatures above 100°C; this equipment was suitable for studying the heat resistance of peroxidase at high temperatures.

Heat Inactivation Kinetics of Trypsin Inhibitors During High Temperature‐Short Time Processing of Soymilk

ABSTRACTHeat treatment of soymilk was studied in the conventional batch boiling process and under High Temperature‐Short Time (HTST) conditions. Reduction in total trypsin inhibitor was assayed enzymatically, and individual inhibitors, the Kunitz and the Bowman‐Birk inhibitor, were assayed by ELISA technique. Standard first‐order reaction kinetics and thermodynamics were applicable for inactivation, and results indicated that the mechanism was not protein unfolding, because entropy changes were zero or negative. The two inhibitors were inactivated at the same rate around 137°C. Therefore, a simple first‐order kinetic model which gave a good, slightly conservative estimate of residual anti‐trypsin activity under HTST conditions could be established.