Thermal behaviour of high amylose cornstarch studied by DSC

The thermal behaviour of high amylose cornstarches (80% amylose content) was studied by DSC using high pressure stainless steel pans in the temperature range between 0-350 degrees C. The number of endotherms and the enthalpy of gelatinization were found to depend on moisture content. Up to four endotherms and one exotherm were determined when the moisture content was above 40%. The meaning of each endotherm has been discussed. The enthalpy of gelatinization was calculated based on the summation of all the gelatinization endotherms and found to increase with increasing water content

Starch gelatinization under shearless and shear conditions

This article reviews the development of studying starch gelatinization under shear and shearless conditions, in particular the technologies used to detect the degree of gelatinization. Advantages and disadvantages of each technology were discussed and then some examples were presented to demonstrate their application. A new technology RheoScope, an instrument that can measure viscosity under shear stress and simultaneously observes variation of starch particles using a microscope, was also introduced. It was found the definition of "gelatinization" could be different for different detection technologies. Under shearless condition full gelatinization of starch needs about ratio of water 3/starch 1, while the gelatinization under shear condition requires less water content since shear stress enhances the processing. The number of endotherm and enthalpy of gelatinization depends on amylose/amylopectin, moisture and lipid content

The potential of a targeted unilateral compound training program to reduce lower limb strength asymmetry and increase performance: a proof-of-concept in basketball

ObjectiveThis study investigates the efficacy of training methodologies aimed at mitigating asymmetries in lower limb strength and explosiveness among basketball players.MethodsThirty male university basketball athletes were enrolled in this research. Initial assessments were made regarding their physical attributes, strength, and explosiveness. Subsequently, the participants were randomly allocated into two groups: an experimental group (EG, n = 15) and a control group (CG, n = 15). Over 10 weeks, the EG engaged in a unilateral compound training regimen, incorporating resistance training exercises such as split squats, Bulgarian split squats, box step-ups, and single-leg calf raises (non-dominant leg: three sets of six repetitions; dominant leg: one set of six repetitions) and plyometric drills including lunge jumps, single-leg hops with back foot raise, single-leg lateral jumps, and single-leg continuous hopping (non-dominant leg: three sets of 12 repetitions; dominant leg: one set of 12 repetitions). The CG continued with their standard training routine. Assessments of limb asymmetry and athletic performance were conducted before and after the intervention to evaluate changes.Results1) Body morphology assessments showed limb length and circumference discrepancies of less than 3 cm. The initial average asymmetry percentages in the single-leg countermovement jump (SLCMJ) for jump height, power, and impulse were 15.56%, 12.4%, and 4.48%, respectively. 2) Post-intervention, the EG demonstrated a significant reduction in the asymmetry percentages of SLCMJ height and power (p < 0.01), along with improvements in the isometric mid-thigh pull (IMTP) test metrics (p < 0.05). 3) The EG also showed marked enhancements in the double-leg countermovement jump (CMJ) and standing long jump (SLJ) outcomes compared to the CG (p < 0.01), as well as in squat performance (p < 0.05).ConclusionThe 10-week unilateral compound training program effectively reduced the asymmetry in lower limb strength and explosiveness among elite male university basketball players, contributing to increased maximal strength and explosiveness

Rheological properties of starches with different amylose/amylopectin ratios

The theological properties of corn starches with different amylose/amylopectin ratios (80/20, 50/50, 23/77, and 0/100) were systematically studied by Haake rheometry. The starches were initially pre-compounded with water to designated moisture content levels using a twin-screw extruder. A single-screw extruder with a slit capillary die was then used to characterize the shear stress and melt viscosity characteristics of sample pellets, as a function of both moisture content (19-27%) and extrusion temperature (110-140 degrees C). The melts exhibited shear thinning behavior under all conditions, with the power law index (0 < n < 1) increasing with increasing temperature and moisture content in the majority of cases. The higher the amylose content, the higher is the viscosity (for example, eta increases from 277 Pa s to 1254 Pa s when amylose content increases from 0% to 80% under a certain condition), which is opposite to the sequence of molecular weight; amylopectin-rich starches exhibited increased Newtonian behavior. These theological behaviors are attributed to the higher gelatinization temperature of amylose-rich starches, and in particular the multiphase transitions that occur in these starches at higher temperatures, and the gel-ball structure of gelatinized amylopectin. (C) 2009 Elsevier Ltd. All rights reserved

Extrusion processing and characterization of edible starch films with different amylose contents

Various edible starch films were prepared via extrusion, with a particular focus on the effects of the amylose content of starches from the same resource (corn) on film processibility and performances. Four corn starches with different amylose contents (4.3-77.4%) were used as model materials. The effects of various extrusion processing conditions, such as temperature, screw speed, feeding rate, and water content were systematically investigated. It was found that, while a higher amylose content increased the difficulty of extrusion processing, this could be overcome by increasing the processing temperature, moisture content, and equilibration time. On the other hand, mechanical testing, differential scanning calorimetry, dynamic mechanical analysis, and microscopy showed that films based on higher amylose starch had better mechanical and thermal properties. The reasons include not only the easy entanglement of long linear amylose chains, but also the retained granular structure in high-amylose films, which may act as self-reinforcement

Maximizing plyometric training for adolescents: a meta-analysis of ground contact frequency and overall intervention time on jumping ability: a systematic review and meta-analysis

Abstract Plyometric training boosts adolescents' jumping ability, crucial for athletic success and health. However, the best total ground contact frequency (TGCF) and overall intervention time (OIT) for these exercises remain unclear. This meta-analysis aims to identify optimal TGCF and OIT in plyometric training for adolescents, focusing on countermovement jump (CMJ) and squat jump (SJ) outcomes. This systematic review encompassed five databases and included 38 studies with 50 randomized controlled experiments and 3347 participants. We used the Cochrane risk assessment tool for study quality and Review Manager 5.4 for data analysis. The current meta-analysis incorporated a total of 38 studies, comprising 50 sets of randomized controlled trials, to investigate the influence of different TGCFs and OITs on plyometric training. The Cochrane risk assessment tool indicated that all the included studies were classified as low risk. Various TGCFs in plyometric training positively affected CMJ and SJ heights in adolescents. The TGCF of less than 900 was ideal for enhancing CMJ, whereas more than 1400 was effective for SJ. The optimal OIT was 400–600 min, specifically, 500–600 min for CMJ and 400–500 min for SJ. Plyometric training improves jumping ability in adolescents. Lower ground contact frequency ( 1400 contacts) is more effective for SJ. Optimal intervention time ranges from 400 to 600 min, with 500 to 600 min benefiting CMJ and 400 to 500 min improving SJ

Effects of training intensity, interval time, and training method on jump height in two stages.

(A) Time × protocol interaction effects on jump height over time in different training intensities. (B) Time × training intensity interaction effects on jump height over time under different training methods. (C) Jump height of the same population receiving different training protocols in two stages.</p

Effects of training intensity, interval time, and training method on jump peak power in two stages.

(A) Time × protocol interaction effects on PPO over time in different training intensities. (B) Time × training intensity interaction effects on PPO over time with different training methods. (C) Comparison of PPOs of the same crowd under different training methods in the two stages.</p

Mean test ± standard deviations (SD), test reliability.

Mean test ± standard deviations (SD), test reliability.</p