Combination of heat treatment and chitosan coating to improve postharvest quality of wolfberry (Lycium barbarum)

The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits.     

采前水杨酸处理对哈密瓜果实防御酶的诱导

采用1.0、2.0、3.0 mmol/L水杨酸分别在"蜜农9号"哈密瓜开花前1周、幼果期(花后2周)、果实迅速膨大期(花后3周)和网纹形成期(花后4周)对植株进行4次喷洒.依次在幼果期、膨大期、网纹形成期和成熟期进行取样.分析不同浓度水杨酸处理后果实体内3种防御性酶活性的变化.结果表明:采前1.0、2.0、3.0 mmol/L水杨酸处理均能有效地提高哈密瓜果实中过氧化物酶(POD)、多酚氧化酶(PPO)和苯丙氨酸解氨酶(PAL)活性,尤其以2.0 mmol/L水杨酸处理酶活性增加最为显著.     

Efficiency of acetic acid and formic acid as a catalyst in catalytical and mechanocatalytical pretreatment of barley straw

In this study, the potential of organic acids (formic acid, acetic acid) in a catalytical and mechanocatalytic conversion of lignocellulosic barley straw to valuable sugars is explored using sulfuric acid as a reference. Acid-catalyzed hydrolysis has been carried out with acid-impregnated samples as well as unmodified barley straw. In the mechanocatalytical approach, pretreatment consists of impregnation with the acid catalyst and mechanical treatment by ball milling following chemical hydrolysis. Straw samples and residues were analyzed by Fourier transform infrared spectrometry (FT-IR) whereas hydrolysate analysis was based on total reducing sugar (TRS) determination following the DNS method and capillary electrophoresis (CE) analysis. The results indicated that acetic acid and formic acid are rather mild acids yielding low TRS levels compared to the reference acid. Mechanocatalytical pretreatment slightly increased TRS yields, but not significantly. Strikingly, sulfuric acid showed an efficient conversion efficiency yielding almost 45% of TRS. Furthermore, this study provided evidence for the acetylation of straw components when acetic acid was used as catalyst. Alkali hydrolysis induced the de-esterification, but revealed no significant increase of TRS yields.     

Effect of sintering temperature on mechanical properties of magnesia partially stabilized zirconia refractory

The optimized sintering conditions for a 3.5 wt% magnesia partially stabilized zirconia (Mg-PSZ) refractory were proposed in our recent research. The influence of the sintering temperature on the development of phase composition, microstructure, densification, thermal expansion and mechanical strength was studied in detail by X-ray diffraction (XRD), scanning electron microscope (SEM), He-pycnometer, high temperature dilatometry and three-point bending test. The samples sintered at 1670 °C had the highest bend strength, the maximum densification, the lowest thermal expansion coefficient (CTE), a homogeneous microstructure and a linear change in thermal expansion.     

Exosomal RNAs: Novel Potential Biomarkers for Diseases—A Review

Exosomes are a subset of nano-sized extracellular vesicles originating from endosomes. Exosomes mediate cell-to-cell communication with their cargos, which includes mRNAs, miRNAs, lncRNAs, and circRNAs. Exosomal RNAs have cell specificity and reflect the conditions of their donor cells. Notably, their detection in biofluids can be used as a diagnostic marker for various diseases. Exosomal RNAs are ideal biomarkers because their surrounding membranes confer stability and they are detectable in almost all biofluids, which helps to reduce trauma and avoid invasive examinations. However, knowledge of exosomal biomarkers remains scarce. The present review summarizes the biogenesis, secretion, and uptake of exosomes, the current researches exploring exosomal mRNAs, miRNAs, lncRNAs, and circRNAs as potential biomarkers for the diagnosis of human diseases, as well as recent techniques of exosome isolation.     

适宜臭氧处理对甜瓜采后品质的影响

以甜瓜西州密25号为实验对象,在温度6~8℃,RH80~85%条件下对甜瓜进行适宜的臭氧处理,通过臭氧发生器按照适宜的臭氧浓度和间隔处理时间在50 L的塑料桶中进行密封40 min处理,每次处理结束后去盖贮藏。研究甜瓜在42 d贮藏期中通过适宜臭氧处理观察其相关品质指标的动态变化,以及适宜臭氧处理对链格孢和镰刀菌的抑菌影响。实验表明:适宜臭氧处理(浓度4.28mg/cm~3、间隔时间24 h)后的甜瓜糖度和硬度平均每天仅下降0.07、0.03%,臭氧对其下降起到了明显的延缓作用,同时降低了42%的失重率,对镰刀菌和链格孢起到很强的抑菌作用且对链格孢有更好的抑菌效果,平均每天仅增长4.04 mm;适宜的臭氧处理对甜瓜采后低温贮藏品质有较好的保持作用,延长了贮藏期。本文为甜瓜采后低温贮藏保鲜提供了一定的理论基础。     

Study of taste-active compounds in the water-soluble extract of mature Cheddar cheese

The chemical composition of the water-soluble extracts of mature Cheddar cheese were identified, with the emphasis on understanding the interplay of compounds contributing to the savoury taste in Cheddar. The ultra-filtered water-soluble extracts of two mature Cheddar cheeses were fractionated by gel permeation chromatography (GPC). By sensory evaluation, two taste-active GPC fractions were identified from each cheese. On the basis of chemical profiling of these fractions, aqueous model tastant mixtures were prepared and sensory omission tests carried out. Glutamic acid, organic acids and mineral salts were the main tastants, whereas the other amino acids had a limited impact on taste. The characteristic umami taste was explained by a synergistic effect of glutamic acid and salts. Matching umami taste intensities were obtained from different concentrations of glutamic acid and salts. Unmasking of a bitter or sweet taste from mixtures of sub-threshold concentrations of amino acids without glutamic acids was also observed.     

Aflatoxin contamination and exposure in processed cereal-based complementary foods for infants and young children in greater Accra,Ghana

In the study, aflatoxin levels were assessed in thirty five (35) cereal-based food products intended for infants and young children. Additionally, the results showed that 71% of the processed foods intended for infants contained AFB₁ (0.18 ± 0.01 to 36.10 ± 0.32 μgkg⁻¹) levels higher than the European Union permissible limits of 0.1 μg kg⁻¹. Aflatoxin intake was estimated using aflatoxin levels in the food products and the estimated individual consumption rates. The study also revealed mixed cereals as having the highest intake of aflatoxin B₁ contaminants (0.005–0.852 μgkg⁻¹bw d⁻¹; 0.004–0.657 μgkg⁻¹bwd⁻¹) with mean estimated daily intake (EDI) of 0.23 ± 0.16 μgkg⁻¹bwd⁻¹ and 0.153 ± 0.13 μgkg⁻¹bwd⁻¹ for infants and young children respectively. The estimated AFT intake recorded for infants and young children for all the cereal-based food ranged from 0.005 to 1.054 μgkg⁻¹bwd⁻¹ and 0.004–0.838 μgkg⁻¹bwd⁻¹ respectively.     

Electrochemical performance study of proton exchange membrane electrolyzer considering the effect of bubble coverage

Bubble dynamics are closely related to the electrochemical performance of a proton exchange membrane electrolyzer (PEMEC). However, tiny bubbles need to be clustered together to affect the electrochemical performance of PEMEC significantly. In this paper, the effect of microscopic bubbles on macroscopic electrochemical properties were assessed by bubble coverage. The bubble dynamics, two-phase flow, and electrochemical performance were captured under different conditions using a high-speed, microscopic visualization experimental system. The results show that various factors influence the two-phase flow pattern. At 60 °C, 1.5 A/cm² and 5 mL/min, the annular flow occupied 76.8% of the gas phase area, and when the water flow increased to 80 mL/min, the annular flow ratio decreased substantially to 2.7%. The two-phase flow of bubbles in the flow channel showed different flow patterns over time. Under the experimental conditions (60 °C, 20 mL/min, 0.8 A/cm²), the bubble flow pattern experienced the emergence of bubbles, bubble flow, segmental plug flow, annular flow, and final steady state with the occurrence times of 0.15 s, 1.5 s, 5.0 s, 10.5 s, and 21.2 s, respectively. The bubble coverage increased with current density and temperature, while it decreased with the increase of water velocity. In addition, the effects of temperature and water velocity on bubble coverage and PEMEC performance vary in principle. Specifically, higher temperature mainly improves the bubble coverage by increasing the electrochemical performance of PEMEC. In contrast, higher water velocity mainly improves the electrochemical performance of PEMEC by decreasing the bubble coverage. This study elucidates the relationship between microscopic bubbles and macroscopic electrochemical performance, contributing to a better understanding of the processes and principles of bubble effects on the electrochemical performance of PEMEC. The results may provide a theoretical basis and experimental data for operating condition optimization, operating efficiency improvement, multiphase flow study, gas diffusion layer structure, and flow field design of PEMEC.