油胞破坏性青花椒干燥过程中叶绿素降解机制

青花椒在快速干燥过程中可以抑制叶绿素的降解,但油胞破坏性青花椒除外。为了探讨这个现象背后的发生机制,本实验将对油胞破坏性青花椒的叶绿素和相关酶的变化进行研究。结果表明,与油胞完整性青花椒相比,干燥后和油胞破坏性青花椒的叶绿素变化更加严重和复杂,干燥后的叶绿素仅剩下原来的6%。油胞破坏抑制了通过脱镁叶绿酸a氧化酶途径形成的焦脱植基叶绿素,并导致脱镁叶绿酸a的在青花椒体内积累（占总叶绿素的18%）。在慢速干燥过程中,逐渐增加的叶绿素降解过氧化物酶活力使得C132氧化型叶绿素的含量不断增加,相关的酶、叶绿素酶和脱镁叶绿素酸酶呈现出下降趋势,而叶绿素降解过氧化物酶和脱镁螯合物则出现波动变化。     

干燥条件对青花椒色泽的影响

为了解不同的干燥条件与青花椒果皮表面油胞的完整性对鲜青花椒干燥后色泽的影响,以鲜青花椒为原料,研究破油胞组、未破油胞组、阴干组这3 种干燥条件对青花椒色泽和叶绿素降解情况的影响。结果表明：不同的干燥条件对干燥后青花椒的色泽均有一定程度的影响,破油胞组干青花椒变色最为严重,阴干组干青花椒变色次之,未破油胞组干青花椒青绿色泽最好;不同干燥条件下,叶绿素的降解产物不完全相同;脱镁叶绿酸等褐色叶绿素降解产物的产生可能是破油胞组与阴干组干青花椒变色的原因之一;干燥过程中,青花椒的色泽参数值与叶绿素a、b含量的变化呈极显著（P＜0.01）正相关关系。     

Impact of UV-B irradiation on chlorophyll degradation and chlorophyll-degrading enzyme activities in stored broccoli (Brassica oleracea L. Italica Group) florets

UV-B irradiation was applied to broccoli florets to investigate its effect on chlorophyll degradation and chlorophyll-degrading enzyme activities in stored broccoli. Broccoli florets were irradiated with UV-B doses at 4.4, 8.8, and 13.1 kJ m⁻² and then kept at 15 °C in darkness. We found that a UV-B dose of at least 8.8 kJ m⁻² efficiently delayed the decrease of the hue angle value and the contents of chlorophylls a and b. Chlorophyllide a and 13²-hydroxychlorohyll a gradually decreased with senescence. Pheophorbide a and pyropheophorbide a levels were significantly higher in broccoli without UV-B treatment. Chlorophyllase and chlorophyll-degrading peroxidase activities with UV-B treatment were suppressed, as well as the activity of Mg-dechelatase. Mg-dechelating substance activity was also suppressed with this treatment. We concluded that UV-B treatment effectively suppressed chlorophyll degradation in broccoli florets during storage, suggesting that the effect could be due to the suppression of chlorophyll-degrading enzyme activities.     

Bleaching of Green Peas and Changes in Enzyme Activities of Seeds under Simulated Climatic Conditions

ABSTRACT: The effects of simulated climatic conditions on green color loss of peas ( Pisum sativum ) and related enzyme activities were investigated. Seeds of 2 green pea cultivars showing different resistance to green color bleaching were subjected to light only, soaking in water without light, and soaking in water with light. Green color loss and chlorophyll loss were highest in seeds soaked in water and exposed to light, less in seeds soaked in water under dark conditions, and least in seeds exposed to light only. Increased chlorophyllase activity was associated with loss of green color and chlorophyll, whereas no significant relationship was found between chlorophyll loss and lipoxygenase or chlorophyll-degrading peroxidase activity. Susceptible and resistant cultivars had significant differences in green color, chlorophyll content, chlorophyll a/b ratio, and chlorophyll degradation kinetics constant when seeds were soaked in water and exposed to light. Enzyme activity was not significantly different between the cultivars. Soaking led to more green color loss, chlorophyll breakdown, and chlorophyllase activity than light exposure. Chlorophyllase may be the key enzyme responsible for green pea bleaching instead of the oxidative chlorophyll degradation pathway with lipoxygenase or chlorophyll-degrading peroxidase.     

微波与护色剂结合处理对自然干制青花椒色泽的影响

为解决青花椒自然干燥过程中极易发黑发褐的问题,提高干制青花椒产品品质,采用微波与护色剂结合处理的工艺。考查不同微波处理条件及结合不同护色剂对自然干制青花椒色泽的影响。结果表明,经微波处理的最佳工艺条件（载料量50g,微波功率462W,微波时间60s）处理后,再结合用含有0.4%异抗坏血酸钠的30%乙醇溶液进行喷涂处理,于室温（28℃,相对湿度为45%）下阴干后,所得干制青花椒△a值可达-5.26,青花椒色泽青绿,护色效果显著。      

单色光照射对鲜青花椒叶绿素降解的实验研究

以鲜青花椒为实验材料,研究了在8种单色光照射下鲜青花椒色泽和叶绿素含量的变化,以确定各种单色光对鲜青花椒叶绿素降解的影响。研究结果表明,在整个单色光光照过程中,鲜青花椒果皮的绿色逐渐褪去,并逐渐变暗;其中,紫外光的照射对鲜青花椒色泽的影响最为明显,其次是蓝色光和黄色光;同时,鲜青花椒的叶绿素逐渐降解,其中对叶绿素a降解有显著影响的单色光依次为紫外光、蓝色光和黄色光,而对叶绿素b降解有显著影响的单色光依次为紫外光、黄色光和蓝色光。另外,青花椒果皮的色差值与青花椒体内总叶绿素的降解率相关系数为0.8380。      

Cold plasma enzyme inactivation on dielectric properties and freshness quality in bananas

Cold plasma (CP) technology is a novel, non-thermal method to inactive enzymes and improve the quality of food materials. In this study, banana samples were processed via CP treatment for different lengths of time (1, 1.5, and 2 min intervals) and their properties, including dielectric properties, enzyme activities, levels of ROS (reactive oxygen species), enzymatic browning products, color, flavor compounds, and surface microstructure, were measured. The dielectric constant (ε′) and loss factor (ε′′) after CP treatment decreased with increasing frequency and increased with increasing temperature, respectively. Higher values of ε′ and ε′′ could also be found after CP treatment. The enzyme activity of polyphenoloxidase (PPO) and peroxydase (POD) decreased with increasing CP treatment time. ROS levels in cells increased after CP treatment, and quinones generated from enzymatic browning decreased at extended treatment times. CP treatment had a positive effect on the surface color of bananas due to enzyme inactivation, while significant differences in a^⁎ and b^⁎ values at different treatment times were noted. However, surface morphology changed with increasing CP processing time, leading to a rougher surface microstructure. CP treatment has little impact on flavor compounds and has demonstrated a potential pretreatment technology for dielectric heating/drying.     

Using drying treatments to stabilise mango peel and seed: Effect on antioxidant activity

The aim of this work was to study the effect of different drying treatments on the antioxidant activity of mango peel and seed. Freeze-drying allowed the peel (when extraction was carried out with ethanol:water) and seed to be stabilised without diminishing their antioxidant activity. In addition, this treatment improved mango peel’s antiradical capacity against ABTS^?+ (in ethanol:water), as well as the capacity of the seed to scavenge free radicals and to inhibit the lipid peroxidation. Oven-drying at 70 °C (with static or forced air) was the treatment that had the most negative effect on the antioxidant capacity of mango peel (when extraction was carried out with ethanol) and seed. Because the effect of drying methods on the phenol and anthocyanin content of mango peel or seed is related to antioxidant activity (with a moderately strong significant correlation, p < 0.003), it can be concluded that the phenol content of both materials is largely responsible for their antioxidant activity.     

Analytical Methods for Enzyme and DPPH Radical Scavenging Activities of Natural Pigments from Some Plants

The enzyme activities in different fractions of Dioscorea japonica Thunb. and 1,1-diphenyl-2-picryl hydrazyl radical scavenging activity in 15 natural plant pigments from black rice, purple sweet potato, yellow bitter melon, yellow paprika, red cabbage, yellow gardenia, blue gardenia, Chinese foxglove, mulberry leave, onion peel, grape peel, mulberry, red beet, gromwell, and cactus were determined. The antioxidant activity in the cosmetic composition of mulberry leaves, grape peel, mulberry, and red cabbage pigments was relatively high in comparison with all other studied plants. Enzyme activities in investigated plants were evaluated as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). The cosmetic composition of mulberry leaf pigment had the highest SOD enzyme activity of 67.1% while onion peel pigment showed the lowest SOD enzyme activity of 15.3%. The activity of CAT and APX from cosmetic composition of natural plant pigments has also been investigated. Both CAT and APX showed higher values in the cactus, mulberry, and red cabbage cosmetic compositions in comparison with other plant pigments. The cosmetic composition in EtOAc extract of D. japonica Thunb. had the highest SOD enzyme activity while the BuOH and EtOH extracts were comparatively low. CAT and APX activities showed significantly high values in EtOH and EtOAc extracts. The antioxidant enzyme activities of D. japonica Thunb. differ significantly in different plant pigments during their extraction. In conclusion, we showed that the plant pigments and D. japonica Thunb. had the potent biological activities. Therefore, these plant resources having anti-aging components could be good materials for development of source of natural cosmetics.     

不同干燥方式对核桃青皮活性物质含量和生物活性的影响

目的研究不同干燥方法对核桃青皮提取物的生物活性物质含量、抗氧化活性和抑菌活性的影响。方法分别采用Folin-Ciocalteu法、硝酸铝显色法和分先先度法测定核桃青皮提取物的多酚含量、黄酮含量和单宁含量;采用自由基清除法和三价铁离子还原法测定抗氧化活性;采用抑菌圈法、最低抑菌浓度值法(minimum inhibitory concentration,MIC)和最低杀菌浓度值法(minimum bactericidal concentration,MBC)测定抑菌活性。结果真空冷冻干燥后的提取物的生物活性成分保留量最大,1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除能力和铁还原能力(ferric reducing antioxidant power,FRAP)均最强,对革兰氏阳性菌的抑制作用强于革兰氏阴性菌;自然干燥后的提取物清除2,2-联氮-二(3-乙基-苯幵噻唑-6-磺酸)二铵盐(2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate),ABTS)自由基的能力最强;红外干燥后的提取物对革兰氏阴性菌的抑制作用强于革兰氏阳性菌。结论不同干燥方式对核桃青皮提取物的生物活性物质的含量和活性均有不同的影响     

Comparing physicochemical properties of banana pulp and peel flours prepared from green and ripe fruits

Banana pulp and peel flour prepared from green and ripe Cavendish banana were assessed for physicochemical properties such as pH, total soluble solids (TSS), water holding capacity (WHC) and oil holding capacity (OHC) at 40, 60 and 80 °C, colour values L^∗, a^∗ and b^∗, back extrusion force (BEF) and viscosity. Data obtained were analysed by MANOVA, discriminant analysis and cluster analysis. All statistical analyses showed that physicochemical properties of flour prepared from pulp and peel, and green and ripe banana were different from each other. TSS, WHC40, WHC60 and BEF can be used to discriminate between peel and pulp flour, whilst TSS and viscosity can be used to discriminate between flour prepared from green and ripe banana.     

Non-stationary drying of carrot: Effect on product quality

This paper presents the results of studies concerning the quality of food materials like vegetables subjected to convective drying in non-stationary conditions. The effect of different frequencies and amplitudes of the periodically changeable drying air temperature on the quality of dried carrot (Daucus carota L.) has been investigated. The indicators of the quality such as the color change, the water activity and the retention of β-carotene were analyzed. The slices of carrot root were used as the material for experimental tests. It has been shown that the non-stationary drying carried out in a prescribed variable air temperature significantly minimized the unfavorable effects in color changes, β-carotene degradation, and decay phenomena.     

不同干燥温度下橘皮的干燥特性及香味变化

为研究不同干燥温度下橘皮的干燥特性及挥发性香味成分变化情况.以橘皮为原料,分析了不同干燥温度下橘皮含水量变化及干燥速率的变化规律,确定了最优的橘皮干燥动力学模型,并考察了干燥温度对橘皮挥发性香味成分的影响.结果表明:橘皮干燥过程主要发生降速干燥,干燥温度越高,干燥所用时间越短,Page模型可较优地描述橘皮的干燥过程;橘...     

Pectinesterase extraction from Mexican lime (Citrus aurantifolia Swingle) and prickly pear (Opuntia ficus indica L.) peels

Extracts from Mexican lime (Citrus aurantifolia Swingle) and prickly pear (Opuntia ficus indica L.) peels were tested for their pectinesterase activity. A factorial design was applied in this study as a method for enzyme extraction in which the variables were the source of enzyme (prickly pear and Mexican lime peels) and the NaCl solution concentration (0–3.0 M). In all cases, enzyme extracts obtained using the same NaCl concentration from lime peel showed higher activity than extracts from prickly pear peel. NaCl concentration influenced the pectinesterase extraction process in both cases. Maximum enzyme activities were obtained with NaCl 0.5 M and 1.0 M for Mexican lime and prickly pear peels, respectively.     

Identification of adenosine deaminase inhibitors from Tofu wastewater and litchi peel and their synergistic anticancer and antibacterial activities with cordycepin

Adenosine deaminase ( ADA) inhibitors regulate cellular levels of adenosine and deoxyadenosine and can be used as anti‐inflammatory and anticancer drugs or degradation inhibitors of adenosine drugs. Screening of natural ADA inhibitors indicated crude extracts from Tofu wastewater and litchi peel showed strong ADA inhibition. Genistin, genistein and daidzein from Tofu wastewater and cyanidin‐3‐rutinoside from litchi peel were purified with simple processes and identified as ADA inhibitors. Structure–activity investigation indicated genistein and cyanidin‐3‐rutinoside had high ADA inhibition at IC₅₀ of 0.4 and 0.6 mg mL^?1, respectively. Genistein and cyanidin‐3‐rutinoside showed synergistic anticancer and antibacterial activities with cordycepin. Docking simulation suggested that genistein and cyanidin‐3‐rutinoside can enter into ADA active site, bind with its functional amino acids through H‐bonds and competitively inhibit the enzyme. This work indicated the extracts from Tofu wastewater and litchi peel, and their active flavonoids from food processing wasters can be used as health food.     

Determination of effective moisture diffusivity and assessment of quality attributes of banana slices during drying

The influence of drying temperatures on the moisture diffusivity and quality attributes of the dried banana slices in terms of volatile compound, shrinkage, color, texture and microstructure were studied. Bananas with peel color index of 5 corresponding to yellow color with green tip were sliced into 3 mm thickness, dipped into ascorbic acid solution and dried at four temperatures of 70, 80, 90 and 100 °C. Drying rate of banana slices can be divided into two sub-drying periods, first and second falling rate periods. The effective diffusivity estimated by the optimization technique was found to decrease sharply with moisture content in the first falling rate period and changed slightly in the second falling rate period. High-temperature drying seems to provide lower loss of volatile compounds in the dried sample. Moreover, the dried banana was very porous, resulting in remarkably lower hardness value than that obtained from the low-temperature drying whilst the crispiness was not significantly different amongst the samples obtained at various drying temperatures. Although the textural property could be improved at high temperature, the product color was brown as manifested by the low L- and hue values in particular at the drying temperature of 100 °C.     

Misting Affects Market Quality and Enzyme Activity of Broccoli During Retail Storage

Vitamin C, enzyme activities, color and texture changed in misted and nonmisted broccoli at 0, 24, 48 and 72 hr intervals during display cabinet storage (18°C). Reduced ascorbic acid (RAA), ascorbate oxidase and peroxidase activities, total chlorophyll extractions, Hunter-lab color and Instron texture measurements were followed. Misting significantly enhanced RAA (p=0.0001), and retention of chlorophyll (p=0.0001), and green color as measured by hue angle (p=0.0021) during 72 hr storage. RAA degradation in misted and nonmisted broccoli and total chlorophyll degradation in nonmisted samples followed first order kinetics. Peroxidase activity was significantly greater in both the nonmisted broccoli floret/stem (p = 0.0221) and stalk tissue (p=0.0079). No significant differences were found between misted and nonmisted broccoli for ascorbate oxidase activity (p = 0.9426) or Instron shear values (p = 0.3652).     

Physicochemical and functional properties of chitosans affected by sun drying time during decoloration

The typical production of chitosan from crustacean shell consists of demineralization, deproteinization, decoloration, and deacetylation. Selected physicochemical and functional properties of chitosans as affected by various decoloration times (4, 5, 6, 7 or 8 h) using sun drying were evaluated. Moisture content (6.67-6.89 g/100 g), degree of deacetylation (81.91-82.73%), and color L^∗ value (78.32-79.43) of chitosans were not affected by sun drying time. However, color a^∗ and b^∗ values decreased when sun drying time was over 4 h. The viscosity of chitosan solution (0.5 g/100 mL acetic acid) decreased gradually with increasing sun drying time, with a more pronounced effect observed at 8 h of sun drying. There was no change in water-binding capacity (WBC) of chitosans decolorized by sun drying between 4 and 6 h; however, further increase in sun drying time from 6 to 7 or 8 h increased WBC of chitosans. DPPH radical scavenging activity of chitosans increased with increasing sun drying time. This study demonstrated that white-colored chitosans could be produced by an alternative decoloration step using sun drying for 4 h following the deacetylation step. However, increasing sun drying time to 7 h produced chitosan with increased WBC and DPPH radical scavenging activity.     

Effect of ethanol treatment on quality and antioxidant activity in postharvest broccoli florets

Broccoli deteriorates very quickly after harvest at ambient temperature due to the loss of green color and the consequent yellowing of florets. To search for an effective method to control quality deterioration, the effect of ethanol treatment on visual quality, antioxidant enzymes and health-promoting compounds in broccoli florets was investigated. Ethanol treatment (500?μL/L) markedly extended shelf-life, inhibited the increase of L ^* value and the decrease of H value. It also reduced the rate of chlorophyll degradation by inhibiting the activities of chlorophyllase, Mg-dechelatase and peroxidase. In addition, the 1, 1-diphenyl-2-picrylhydrazyl radical scavenging activity and the activities of superoxide dismutase, ascorbate peroxidase and catalase were enhanced in florets treated with ethanol. The contents of total phenolic compounds, glucosinolates and sulforaphane in broccoli were also profoundly increased after treating with ethanol. These results indicated that a postharvest application of ethanol can prolong shelf-life, maintain visual quality and enhance the nutritional value of broccoli florets.     

Combination of digital images and laser light to predict moisture content and color of bell pepper simultaneously during drying

Optical devices are being increasingly used for more accurate and faster ways to investigate quality parameters of agricultural products. The main task of this research is to evaluate the use of a CCD camera in combination with laser diodes emitting at 532 nm and 635 nm to monitor changes in moisture content of red, yellow and green bell pepper during drying. Moreover, the feasibility of using the CCD camera alone to analyze color changes during drying, in alternative to the colorimeter, is assessed. Results showed that scattering area and light intensity were able to predict moisture content changes of bell pepper during drying. While excellent correlations were obtained for yellow colored samples (R = 0.93 and RMSEP = 7.28), the behavior of green and red wavelengths in peppers with red and green color, respectively, may raise some doubt on the ability to predict moisture content (R = 0.33 and RMSEP > 22). Additionally, light scattering varied according to the different depths on the surface where the images were taken. Furthermore, it was concluded that a change in tissue structure during drying may have caused dispersion of photons through the surface resulting in varying degrees of scattering. The presented technique based on a digital camera and laser diodes shows the potential to be applied in the future as a fast and modern method for in-line measurements of monitoring moisture content during drying. Digital images in terms of RGB values have been demonstrated to be a promising alternative to monitor changes of L^∗ (R = 0.87 and R = 0.90), and a^∗ values (R = 0.93 and R = 0.97), during drying of yellow and green pepper. Extensive studies are still required to determine the suitability of digital images for analysis of b^∗ values at different colors of bell pepper.