Dajing Li

Analysis of (all-E)-lutein and its (Z)-isomers during illumination in a model system

Light induced-isomerization of (all-E)-lutein in organic solvent and starch model systems was investigated. Lutein and its (Z)-isomers were separated by HPLC using a C30 column and gradient mobile phase based on methanol-methyl-tert-butyl ether-water in 24min. (All-E)-lutein and twelve (Z)-isomers of lutein, in addition a small amount of (all-E)-zeaxanthin and (9Z, 9Z)-zeaxanthin were identified by HPLC-DAD-APCI-MS. Five di-(Z)-luteins were identified for the first time, namely, (9Z, 9Z)-, (9Z, 13Z)/(9 Z, 13Z)-, (13Z, 15Z)- and (9Z, 15Z)-lutein and (9Z, 9Z)-zeaxanthin. A mixture of (9Z)-lutein and of (9Z)-lutein was the main product of the iodine-catalyzed photo-isomerization. (9Z, 13Z)/(9Z, 13Z)-lutein were the major di-(Z)-isomers of lutein formed. The susceptibility of lutein to degradation was much less under dark storage than under lighted storage in starch model system. Isomerization and degradation of lutein and its (Z)-isomers proceeded simultaneously in all the model systems.

Effects of ultrasound pretreatment on drying kinetics and quality parameters of button mushroom slices

ABSTRACT The aim of this study was to investigate the utilization of ultrasound as a pretreatment method prior to drying to improve the quality of button mushroom slices during both hot air drying and far infrared drying processes. The effects of ultrasound and blanching pretreatments upon drying were analyzed. The ultrasound frequency was 40 kHz, the power was 0.4 W/cm2, and the ultrasound energy was applied for 3 and 10 min, respectively. The ultrasound treatment caused reduction of the drying time by 9.5% in comparison to untreated samples. The drying kinetics of button mushroom slices were improved by ultrasound application, which involved an improvement of mass transfer coefficient and effective moisture diffusivity. The logarithmic model showed the best fit to the experimental drying data. For ultrasound treated samples, the parameters including hardness, crispness, rehydration ability, shrinkage, microstructure, and nutrient composition had remarkable changes compared with blanched and untreated samples.

Protective Effects of Blueberry Anthocyanins against H2O2-Induced Oxidative Injuries in Human Retinal Pigment Epithelial Cells

Blueberry anthocyanins are considered protective of eye health because of their recognized antioxidant properties. In this study, blueberry anthocyanin extract (BAE), malvidin (Mv), malvidin-3-glucoside (Mv-3-glc), and malvidin-3-galactoside (Mv-3-gal) all reduced H2O2-induced oxidative stress by decreasing the levels of reactive oxygen species and malondialdehyde and increasing the levels of superoxide dismutase, catalase, and glutathione peroxidase in human retinal pigment epithelial cells. BAE and the anthocyanin standards enhanced cell viability from 63.69 ± 3.36 to 86.57 ± 6.92% (BAE), 115.72 ± 23.41% (Mv), 98.15 ± 9.39% (Mv-3-glc), and 127.97 ± 20.09% (Mv-3-gal) and significantly inhibited cell apoptosis (P < 0.01 for all). Mitogen-activated-protein-kinase pathways, including ERK1/2 and p38, were involved in the bioactivities. In addition, the anthocyanins decreased vascular-endothelial-cell-growth-factor levels and activated Akt-signal pathways. These combined results supported the hypothesis that blueberry anthocyanins could inhibit the induction and progression of age-related macular degeneration (AMD) through antioxidant mechanisms.

Light-induced oxidation and isomerization of all-trans-β-cryptoxanthin in a model system

The oxidation and isomerization of all-trans-β-cryptoxanthin as affected by iodine-catalysed illumination and non-iodine-catalysed illumination were studied. Seven cis-isomers and two oxidation products were separated by HPLC method using a C30 column. The identification and structural elucidation of the compounds were determined by HPLC-DAD-APCI-MS. Five compounds were identified in details for the first time, namely, β-β-carotene-3-one, 5,6-epoxy-β-β-carotene-3-one, 13,15-di-cis-, 9,13-di-cis- and 9,9-di-cis-β-cryptoxanthin. Sum of 13- and 13-cis-β-cryptoxanthin was the major cis-isomer of β-cryptoxanthin formed, accounting for 59.0% and 30.6%, respectively. The formation of di-cis isomers may prefer in the present of iodine. 13,15-di-cis-β-cryptoxanthin was the major di-cis-isomer of the iodine-catalysed photo-isomerization.

Thermal degradation kinetics of all- trans and cis -carotenoids in a light-induced model system

Thermal degradation kinetics of lutein, zeaxanthin, β-cryptoxanthin, β-carotene was studied at 25, 35, and 45°C in a model system. Qualitative and quantitative analyses of all-trans- and cis-carotenoids were conducted using HPLC-DAD-MS technologies. Kinetic and thermodynamic parameters were calculated by non-linear regression. A total of 29 geometrical isomers and four oxidation products were detected, including all-trans-, keto compounds, mono-cis- and di-cis-isomers. Degradations of all-trans-lutein, zeaxanthin, β-cryptoxanthin, and β-carotene were described by a first-order kinetic model, with the order of rate constants as kβ-carotene>kβ-cryptoxanthin>klutein>kzeaxanthin. Activation energies of zeaxanthin, lutein, β-cryptoxanthin, and β-carotene were 65.6, 38.9, 33.9, and 8.6kJ/moL, respectively. cis-carotenoids also followed with the first-order kinetic model, but they did not show a defined sequence of degradation rate constants and activation energies at different temperatures. A possible degradation pathway of four carotenoids was identified to better understand the mechanism of carotenoid degradation.

Effect of Thermosonic Pretreatment and Microwave Vacuum Drying on the Water State and Glass Transition Temperature in Agaricus bisporus Slices

This study aimed to understand the micromechanism of thermosonic pretreatment and microwave vacuum drying on Agaricus bisporus. The water state and glass transition temperature (Tg) of fresh and thermosonically treated Agaricus bisporus slices during microwave vacuum drying were studied using differential scanning calorimetry (DSC), low-field nuclear magnetic resonance (LF-NMR), and magnetic resonance imaging (MRI). Results showed that four population groups were contained in the initial distribution of transverse relaxation time (T2) data of fresh A. bisporus slices: T21 (0.38–7.05xa0ms), T22 (9.33–32.75xa0ms), T231 (37.65–265.61xa0ms), and T232 (305.39–811.13xa0ms). Thermosonic pretreatment significantly decreased the initial free water content of A. bisporus sample but was accompanied by a sharp increase in its immobilized water. “Semi-bound water transfer” appeared during microwave vacuum drying (MVD) at moisture contents (Xw) of 0.70 and 0.60 g/g (wet basis (w.b.)) for untreated and thermosonically treated samples, respectively. MVD caused dramatic changes in the water state and enhanced the Tg by decreasing the content and mobility of immobilized water in A. bisporus tissues. The mobility of semi-bound water for thermosonically and MVD-treated samples was higher than for MVD-untreated samples, resulting in Tg values decreasing by approximately 2–11.5xa0°C, but the uniformity of water distribution in thermosonic-treated and MVD-treated samples was better at Xwxa0≤xa00.52 g/g (w.b.).

Identification and Quantification of All-Trans-Zeaxanthin and Its Cis-Isomers During Illumination in a Model System

The degradation and isomerization of all-trans-zeaxanthin in a model system during illumination, in the absence or presence of iodine, were investigated. A high-performance liquid chromatography method was developed using the C-30 column to separate all-trans-zeaxanthin and its cis-isomers. Three mono-cis-isomers and four di-cis-isomers were assigned by high-performance liquid chromatography-photo diode array detection-atmospheric pressure chemical ionization-mass spectrometry (HPLC-DAD-APCI-MS), namely, 15/15’-cis-, 13/13’-cis-, 9/9’-cis-13,15-di-cis-, 9,15-di-cis-, 9,13-di-cis-, and 9,9’-di-cis-zeaxanthin. 13/13’-cis- and 9, 13-di-cis-zeaxanthin were the major cis-isomers of zeaxanthin formed during illumination. Di-cis-zeaxanthin was favored during illumination in the presence of iodine. The degradation of total amount of all-trans-zeaxanthin during illumination was found to fit a first-order model. The degradation rate of iodine-catalyzed photoisomerization of all-trans-zeaxanthin was faster than that of non-iodine-catalyzed photoisomerization. Isomerization and degradation of all-trans-zeaxanthin and its cis-isomers during illumination proceeded simultaneously.

Dielectric properties of Agaricus bisporus slices relevant to drying with microwave energy

ABSTRACT Dielectric properties of sliced Agaricus bisporus samples, with 0.16–0.89 [g/g, wet basis (w.b.)] moisture content, were determined using a network analyser and an open-ended coaxial-line probe, over a frequency range of 915 MHz to 2450 MHz and a temperature range of 25°C to 60°C. The results showed that the permittivity of A. bisporus was a function of frequency, moisture content, and temperature. The dielectric constant and loss factor were directly proportional to moisture content and temperature, respectively, and both decreased with increasing frequency. However, the influence of temperature on the dielectric constant showed a different trend, as this was affected by the moisture content of the sample. The dielectric loss factor initially increased and then decreased with the decrease in moisture content. Both inflection points appeared at the moisture content value of 0.69 (g/g, w.b.), which represents the “semi-bound water transfer” point. Third-degree polynomial models could be used to describe dielectric constant and loss factor values as functions of moisture content and temperature. The penetration depth decreased with increasing frequency and temperature; however, this first decreased with decreasing moisture content and then increased. Notably, the penetration depth was at a low ebb when the moisture content ranged from 0.69 to 0.52 (g/g, w.b.), indicating easier uneven drying. Low frequency (915 MHz) with large penetration depth represents a highly effective method for large-scale industrial dielectric microwave drying of A. bisporus slices from the angle of uniformity.

Ultrasound-assisted osmotic process on quality of microwave vacuum drying sweet potato

ABSTRACT The effects of pretreatment before microwave vacuum drying (MVD) on texture, color, expansion, rehydration, drying rate, microstructure, sensory evaluation, and other properties of sweet potato were investigated in this study. The pretreatment consisted in five processing conditions, using blanching; osmotic dehydration at 35°Brix of sucrose (OD); ultrasound in distilled water (US); ultrasound in distilled water before osmotic dehydration (USu2009+u2009OD), and ultrasound-assisted osmotic dehydration (USOD). Pretreatments of sweet potato before MVD have shown success in reducing drying time with US treatment relatively more effective regarding drying time than other treatments. Compared with other treatments, US showed the highest rehydration ratio values. The osmotic group pretreatment exhibited a pronounced effect on water loss and solid gain, improved the color, aroma, and taste of dried sweet potato, whereas sucrose impregnation resulted in a hard texture observed with OD sample. USOD samples had a higher expansion ratio, lower hardness and color difference values, appeared less cell damaged, and recorded better overall quality than the other samples. There was a slight difference between USOD and USu2009+u2009OD samples. Combining osmotic dehydration with ultrasound as a pretreatment can significantly accelerate the heat transfer rate, reducing the dried time accordingly and increasing energy efficiency.

Screening Quality Evaluation Factors of Freeze-Dried Peach (Prunus Persica L. Batsch) Powders from Different Ripening Time Cultivars

The quality evaluation of processed products is complex. To simplify the quality evaluation process and improve the efficiency, fourteen evaluation factors of freeze-dried powders of seventeen cultivars of peach at different ripening times were analyzed. The most important evaluation indicators and criteria were obtained by analysis of variance (ANOVA), correlation analysis (CA), principal component analysis (PCA), system cluster analysis (SCA), and analytic hierarchy process (AHP). Results showed that the peach powders had the significant differences in quality ( ), and some processing factors were related with some physicochemical and nutritional factors. Five principle components were extracted by PCA and the cumulative contribution achieved was 84.46%. Through the score plot of the first two principal components, a clear differentiation among ripening times was found and three distinct groups were separated according to ripening time. Five characteristic factors were obtained as titratable acid, browning index, hemicellulose, hygroscopicity, and vitamin C by SCA. Their weights of 0.1249, 0.3007, 0.0514, 0.4916, and 0.0315 were obtained by AHP, respectively. The peach cultivars were divided into four evaluation grades by the comprehensive quality score.