Effect of natamycin in combination with pure oxygen treatment on postharvest quality and selected enzyme activities of button mushroom (Agaricus bisporus)

The combined effects of natamycin (NA) and pure oxygen (PO) treatment on microbial and physicochemical characteristics of button mushroom ( Agaricus bisporus ) stored at 4 ± 1 °C for 16 days was investigated. Mushroom respiration rate, weight loss, firmness, color, percent open caps, total soluble solids, microbial and activities of polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), and peroxidase (POD) were measured. The results indicate that treatment with natamycin + pure oxygen (NAPO) maintained tissue firmness, inhibited increase of respiration rate, delayed browning and cap opening, and reduced microorganism counts of yeasts and molds compared to control treatment. The efficiency was better than that of NA or PO treatment. Furthermore, NAPO inhibited the activities of PPO, PAL, and POD throughout the storage period. Our study suggests that NAPO treatment has the potential to improve the quality of button mushroom and extend the shelf life.     

Effect of ultrahigh hydrostatic pressure on the activity and structure of mushroom (Agaricus bisporus) polyphenoloxidase

High hydrostatic pressure (HHP, treatment pressure ≤700 MPa) is approved to be the most successful commercial nonthermal processing due to its minimal modifications in nutritional and sensory quality. However, for some pressure stable enzymes such as PPO, this unique technology can hardly inactivate them at treatment pressure below of 700 MPa. This study investigated the effects of ultrahigh hydrostatic pressure (UHHP, treatment pressure >700 MPa) on the activity of Agaricus bisporus mushroom polyphenoloxidase (PPO) both in the phosphate buffer and in the mushroom puree, and on the structure of the enzyme by means of circular dichroism (CD), fluorescence emission spectra, and sulphydryl group detection. The results showed that UHHP treatment at pressure from 800 to 1600 MPa caused significant inactivation on the PPO both in the phosphate buffer and in the mushroom puree. UHHP treatment at 1400 and 1600 MPa for 1 min reduced the enzyme activity by 90.4% and 99.2% in the buffer;, however, higher enzyme activity remained in the puree after UHHP treatment at the same condition. CD and fluorescence spectra analysis showed that the secondary and tertiary structures of UHHP treated mushroom PPO were changed. The sulphydryl group (SH) detection revealed that the SH content on the surface of UHHP treated mushroom PPO was increased. It has been suggested that the inactivation of mushroom PPO by UHHP treatment at pressure higher than 1000 MPa was due to the synergistic effect of the pressure and the heat arising from pressurization, in which heat plays a major role.     

水分胁迫对温室双孢菇动态发育品质及水分利用效率的影响

为研究基质水分胁迫对双孢菇全育期内菇形的动态发育、产菇品质的影响,确定温室双孢菇适宜、高效的施水方案,以"奥吉1号"品种为试验材料,于2020年8月进行双孢菇全育期基质水分胁迫试验。该试验设置正常T1(基质饱和持水率的80%～90%)、轻度水分胁迫T2(基质饱和持水率的70%～80%)、中度水分胁迫T3(基质饱和持水率的60%～70%)、重度水分胁迫T4(基质饱和持水率的50%～60%)4种水分处理方案,出菇期测定双孢菇发育动态、单菇品质、区域产菇品质、产量与水分利用效率(Water Use Efficiency,WUE)。结果表明:1)菇盖与菇柄的形态指标、出菇品质与基质含水量呈正相关,菇高受水分胁迫影响不明显。2)盖厚、茎粗、菇高的发育经历逐渐增长、快速增长和缓慢增长3个阶段。在T4水处理下菇厚、茎粗的最大值比T1水处理减少26.1%、24.9%,出菇时间延迟16.5 h(P0.05)。随着水分胁迫的加剧,菇柄与菇盖的生长速率峰值逐步提前,迅速增长期延长。3)在T2水处理下,双孢菇WUE和产菇数最高,相比T1水处理提高2.3%和9.2%(P0.05),出菇产量和优质菇率略低于T1水处理。4)双孢菇结菇前期和后期可进行轻度水分胁迫提高WUE,形成耐旱机制。快速发育期内应保持基质充足含水量,以提高双孢菇品质,加快出菇时间。该研究为双孢菇水分精准管理提供理论依据。     

Enzyme inactivation analysis for industrial blanching applications: comparison of microwave, conventional, and combination heat treatments on mushroom polyphenoloxidase activity.

Browning reactions in fruits and vegetables are a serious problem for the food industry. In mushrooms, the principal enzyme responsible for the browning reaction is polyphenoloxidase (PPO). Microwaves have recently been introduced as an alternative for the industrial blanching of mushrooms. However, the direct application of microwave energy to entire mushrooms is limited by the important temperature gradients generated within the samples during heating, which can produce internal water vaporization and associated damage to the mushrooms texture. A microwave applicator has been developed, whereby irradiation conditions can be regulated and the heating process monitored. Whole edible mushrooms (Agaricus bisporus) were blanched by conventional, microwave, and combined heating methods to optimize the rate of PPO inactivation. A combined microwave and hot-water bath treatment has achieved complete PPO inactivation in a short time. Both the loss of antioxidant content and the increase of browning were minor in the samples treated with this combined method when compared to the control. This reduction in processing time also decreased mushroom weight loss and shrinkage.     

Characterization of phytase activity from cultivated edible mushrooms and their production substrates

Phytase is used commercially to maximize phytic acid degradation and to decrease phosphorus levels in poultry and swine manure. To determine phytase content in edible mushrooms, basidiomata of Agaricus bisporus and three specialty mushrooms (Grifola frondosa, Lentinula edodes, and Pleurotus cornucopiae) and spent mushroom substrate (SMS) were surveyed. Enzyme activity ranged from 0.046 to 0.074 unit/g of tissue for four A. bisporus types (closed and open whites and closed and open browns) grown at The Pennsylvania State University's Mushroom Test Demonstration Facility (MTDF). The addition of various nutrient supplements to phase II mushroom production substrate did not alter phytase activity in A. bisporus. Portabella mushrooms (open brown) obtained from a commercial farm had significantly higher levels of phytase activity (0.211 unit/g of tissue) compared to A. bisporus grown at the MTDF. Of the specialty mushrooms surveyed, maitake (G. frondosa) had 20% higher phytase activity (0.287 unit/g of tissue) than commercial portabella mushrooms. The yellow oyster mushroom (P. cornucopiae) ranked second in level of phytase activity (0.213 unit/g of tissue). Shiitake (L. edodes) contained the least amount of phytase in basidiomata (0.107 unit/g of tissue). Post-crop steam treatment (60 degrees C, 24 h) of SMS reduced phytase activity from 0.074 to 0.018 unit/g. Phytase was partially purified from commercially grown portabella basidiomata 314-fold with an estimated molecular mass of 531 kDa by gel filtration chromatography. The optimum pH for activity was 5.5, but appreciable phytase activity was observed over the range of pH 5.0-8.0. Partially purified A. bisporus phytase was inactivated following a 10-min incubation at > or =60 degrees C.     

不同压块模式对双孢菇生产的影响

中国双孢菇栽培工艺较为传统,产量不高,为了促进以牛粪和麦秸为主要原料的食用菌基质化利用效率,开展了双孢菇栽培基质压块工艺的试验研究。本试验采用传统工艺(方案1)和2种基质压块工艺(方案2:紧实度400 kg/m3,方案3:紧实度500 kg/m3)的双孢菇栽培效果进行对比。结果表明,方案1出菇时间为36 d,方案2和方案3出菇时间为38 d,压块工艺使出菇时间延长2 d但并不会影响双孢菇的正常生产;方案1、2、3的双孢菇单产分别为0.198、0.205和0.279 kg/kg,方案3提升最为显著,单产提高了40.9%;方案1、2、3的双孢菇栽培实际面积分别为5.4 m2、4.7 m2和3.8 m2,随着压块工艺紧实度的增加节约栽培占地面积越多;方案1、2、3的双孢菇总产量分别为22.5 kg、23.3 kg和31.7 kg。综合以上结果,本研究认为方案3为最优基质压块工艺,有效的提高了双孢菇产量、节约了栽培面积、降低了成本,该研究为基质压块工艺的实际应用奠定了理论基础。     

双孢蘑菇片气调干制工艺优化研究

以提高双孢蘑菇片干制质量为目的，采用自制小型气调干燥试验设备，以CO₂、N₂置换部分空气作为干燥介质对双孢蘑菇片进行干制对比试验。采用正交试验方法，分析了不同干燥介质对双孢蘑菇片干制质量的影响。结果表明，在干燥室气体的O₂含量相同条件下，以N₂置换部分空气为干燥介质，可提高双孢蘑菇片的脱水率，干制品褐变度降低、维生素C保存率较高。用均匀试验设计回归分析程序拟合产品的褐变度、维生素C和ADF质量分数随干燥室气体O₂含量、干制温度和干制时间变化的回归方程，置信水平达95%，可用于指导实际生产。     

Thermal and high-pressure inactivation kinetics of polyphenol oxidase in Victoria grape must

The inactivation kinetics of polyphenol oxidase (PPO) in freshly prepared grape must under high hydrostatic pressure (100-800 MPa) combined with moderate temperature (20-70 degrees C) was investigated. Atmospheric pressure conditions in a temperature range of 55-70 degrees C were also tested. Isothermal inactivation of PPO in grape must could be described by a biphasic model. The values of activation energy and activation volume of stable fraction were estimated as 53.34 kJ mol(-1) and -18.15 cm3 mol(-1) at a reference pressure of 600 MPa and reference temperature of 50 degrees C, respectively. Pressure and temperature were found to act synergistically, except in the high-temperature-low-pressure region where an antagonistic effect was found. A third-degree polynomial model was successfully applied to describe the temperature/pressure dependence of the inactivation rate constants of the stable PPO fraction in grape must.     

Lignin degradation by Agaricus bisporus accounts for a 30% increase in bioavailable holocellulose during cultivation on compost

The common mushroom Agaricus bisporus is a non-white rot saphrophytic fungus that can degrade lignin to free and utilize holocellulose embedded in fermented straw as present in compost. A new method is described to estimate the actual amount of bioavailable holocellulose in 3.8 kg compost cultures spawned with A. bisporus Horst U1 prior to and during a cultivation with two cycles of mushroom harvesting. The method shows that the initial amount of bioavailable holocellulose per culture, accounting for 130 +/- 22 g, is lower than the total holocellulose consumption by A. bisporus accounting for 182 +/- 15 g. This difference is explained by a 30% increase in bioavailable holocellulose. The increase is caused by the degradation of 95 +/- 3 g of holocellulose-shielding lignin. The results are discussed within the scope of the A. bisporus mushroom yield and lignin degradation by white rot fungi during growth on lignocellulose-containing materials.     

Effects of stage of maturity and cooking on the chemical composition of select mushroom varieties

Select mushrooms were analyzed for proximate constituents and carbohydrate profiles either raw or cooked and at different stages of maturity. White button mushrooms (Agaricus biporus) contained high concentrations of ash (12.5 and 11.9% for immature and mature mushrooms, respectively). Starch and total dietary fiber (TDF) concentrations were higher in maitake (Grifola frondosa) and shiitake (Lentinus edodes) mushrooms. Crude protein (CP) and acid-hydrolyzed fat (AHF) were highest in crimini (Agaricus bisporus) and white button and maitake mushrooms, respectively. Chitin concentrations were highest in portabella (Agaricus bisporus) and enoki (Flammulina velutipes) mushrooms (8.0 and 7.7%, respectively). Oligosaccharides were found in low concentrations in some mushrooms. CP and TDF accounted for 86.4 and 49.3% of mushroom organic matter. Cooking increased starch, TDF, and AHF but decreased CP and chitin concentrations. The chitin concentration increased with mushroom maturity. These results detail the complete carbohydrate profile of several important mushroom varieties.     

Thermal inactivation of mushroom polyphenoloxidase employing 2450 MHz microwave radiation.

Browning reactions in fruits and vegetables are a serious problem for the food industry. In mushrooms, the principal enzyme responsible for the browning reaction is polyphenoloxidase (PPO). A microwave applicator has been designed and used for studying mushroom PPO inactivation. The effects of microwaves and conventional heating on the kinetics of the monophenolase and diphenolase activities of PPO were studied. Conventional and microwave treatments produce different enzyme intermediates with different stability and kinetic properties. We describe how considerable time can be saved during microwave inactivation of the enzyme compared with the time needed when conventional hot-water treatment is used, resulting in greater profitability and enhanced quality. The short exposure time required for samples irradiated with microwaves is very important for maintaining the quality of mushrooms. The fast microwave treatment used resulted in an increase in antioxidant content and a considerable decrease in browning.     

Chitin and chitosan--value-added products from mushroom waste

Accumulation of chitinous material in Agaricus bisporus stalks was determined during postharvest storage at 4 and 25 degrees C. The chitinous material was extracted after alkali treatment and acid reflux of alkali insoluble material and analyzed for yield, purity, degree of acetylation (DA), and crystallinity. The total glucosamine content in mushroom stalks increased from 7.14% dry weight (DW) at harvest (day 0) to 11.00% DW and 19.02% DW after 15 days of storage at 4 degrees C and 5 days of storage at 25 degrees C, respectively. The yield of crude chitin isolated from stalks stored at 25 degrees C for 5 days was 27.00% DW and consisted of 46.08% glucosamine and 20.94% neutral polysaccharides. The DA of fungal chitin was from 75.8 to 87.6%, which is similar to commercially available crustacean chitin. The yield of crude fungal chitin of 0.65-1.15% on a fresh basis indicates the potential for the utilization of these mushroom byproducts.     

气调贮藏对双孢蘑菇细胞超微结构的影响

为了揭示气调贮藏抑制双孢蘑菇褐变的作用机理,采用透射电镜法对气调贮藏条件下双孢蘑菇细胞超微结构的变化进行观察,分析了双孢蘑菇细胞超微结构完整性与组织褐变度之间的关系,结果表明:双孢蘑菇贮藏过程中组织细胞的完整性与褐变度密切相关,适宜的气调环境能够显著抑制双孢蘑菇贮藏过程组织细胞的降解,从而延缓组织褐变。     

番茄地套作蘑菇对土壤肥力和生物活性的影响

通过温室盆栽试验,研究了套作双孢蘑菇(Agaricus bisporus)对潮土速效养分含量、微生物数量、关键酶活性以及番茄(Lycopersicon esculentum Mill.)生长的影响。结果发现,与对照相比,添加双孢蘑菇培养基质对土壤有机碳、矿质氮与速效磷含量均没有显著影响,但速效钾含量显著增加(P<0.05),且土壤细菌数量趋于增加、真菌数量显著减少(P<0.05),土壤脲酶与磷酸酶活性显著增强(P<0.05)、纤维素酶活性显著下降(P<0.05),番茄植株地上部和地下部生物量分别增加130%和67%,但产量没有明显变化;在添加培养基质基础上再接种双孢蘑菇菌种与不接种相比显著降低土壤有机碳含量和脲酶活性(P<0.05),番茄植株生物量也降到与对照相接近的水平,尽管番茄产量没有明显变化,但额外收获了双孢蘑菇。结果表明,套作双孢蘑菇对潮土生物活性具有促进作用,并可以增加单位面积经济产出,因而在潮土地区具有推广潜力。     

Influence of pH, benzoic acid, glutathione, EDTA, 4-hexylresorcinol, and sodium chloride on the pressure inactivation kinetics of mushroom polyphenol oxidase.

Pressure inactivation of mushroom PPO was studied for pH values ranging from 4 to 8, and the effect of some antibrowning agents on the pressure stability of mushroom PPO at pH 6.5 was evaluated. pH reduction below 6.5 resulted in a lowered inactivation threshold pressure and an increase of the absolute value of the activation volume (or a decrease of the z(p) value), the latter two parameters reflecting the pressure dependency of the inactivation rate constant. An increase in pH from 6.5 to 8, on the other hand, did only marginally affect the pressure stability of the enzyme. Mushroom PPO at pH 6.5 was markedly sensitized toward pressure by the presence of 2.5 mM 4-hexylresorcinol and slightly stabilized by the presence of 5 mM EDTA. The presence of 5 mM glutathione, sodium chloride, or benzoic acid caused no significant alteration of the enzyme pressure stability. Only in the presence of 4-hexylresorcinol, significant changes of the activation volume and z(p) value were noticed.     

双孢蘑菇工厂化生产关键配套装置设计与试验

针对双孢蘑菇工厂化生产过程中有关二次发酵培养料装盘-码盘,托盘在育菇床架收布及双孢蘑菇采摘3个关键作业环节,分别设计了与各环节相配套的培养料连续装盘-码盘装置、培养料托盘机械化收布装置及与机械式育菇床架配合使用的移动式采菇滑车等作业装置,结合双孢蘑菇栽培技术要求确定了该配套装置各关键部件设计参数,并进行了作业性能测试。装置性能试验结果表明:设计的相关作业环节配套装置运行可靠、稳定,培养料压实厚度保持在269.8~281.5 mm,紧实度均值达到491.4 kg/m3,压实均匀性保持在97.38%~99.62%之间,压实效果满足双孢蘑菇后续工厂化生产需求;涉及3个工段的装置基本运行生产时间不超过5 min,提高了双孢蘑菇工厂化生产效率;设计装置产量效应显著,配套装置栽培双孢蘑菇的小区产量均值可达17.61 kg/m2,较传统人工栽培提高了5.79 kg/m2。研究结果将为双孢蘑菇工厂化生产配套装置的设计研发提供参考。     

双孢菇片微波真空干燥特性及工艺优化

为解决双孢菇的干制问题,采用微波真空干燥技术对双孢菇片进行干燥试验,研究双孢菇片的干燥特性,并与热风干燥、真空干燥和冷冻干燥方法进行比较。研究结果显示,微波真空干燥时,微波强度对双孢菇片的干燥速率有显著影响,而真空度影响较小,最优的干燥参数为：微波强度为17.4 W/g,真空度70 kPa,干燥时间20 min,含水率可达6.9%。通过对比4种干燥方法的干制时间及产品的复水率、色泽和维生素C含量,可知微波真空干燥的菇片品质接近冷冻干燥,明显优于热风干燥和真空干燥,而微波真空干燥在干制时间方面要比冷冻干燥明显缩短。微波真空干燥是适合双孢菇片的有潜力的干制技术。     

Agaricus blazei (class Basidiomycotina) aqueous extract enhances the expression of c-Jun protein in MCF7 cells

The edible mushroom Agaricus blazei Murill is considered a health food in many countries after it was reported to be a source of antitumor and immunoactive compounds. An aqueous extract (AE) from this basidiomycete significantly enhanced the expression of the c-Jun/activator protein-1 (AP1) in the human breast cancer cell line MCF7. Incubating the cells with 17-beta-estradiol (E2), p-nonylphenol (NP), and the AE combined, or NP plus the AE, resulted in increased cell proliferation compared to the untreated control by 93 and 67%, respectively. However, incubating the cells with the extract alone did not enhance cell division. It is suggested that the enhanced proliferation of MCF7 cells in the presence of NP and the AE may be due to the involvement of an AP1 gene regulatory complex. This is the first report showing enhanced c-Jun/AP1 expression in MCF7 cells incubated with an aqueous fungal extract.     

Purification and characterization of polyphenol oxidase from rape flower

The purification and partial enzymology characteristics of polyphenol oxidase (PPO) from rape flower were studied. After preliminary treatments, the crude enzyme solution was in turn purified with ammonium sulfate, dialysis, and Sephadex G-75 gel chromatography. The optimal conditions and stability of PPO were examined at different pH values and temperatures. Subsequently, PPO was also characterized by substrate (catechol) concentrations, inhibitors, kinetic parameters, and molecular weight. Results showed that the optimal pH for PPO activity was 5.5 in the presence of catechol and that PPO was relatively stable at pH 3.5-5.5. PPO was moderately stable at temperatures from 60 to 70 °C, whereas it was easily denatured at 80-90 °C. Ethylenediaminetetraacetic acid, sodium chloride, and calcium chloride had little inhibitive effects on PPO, whereas citric acid, sodium sulfite, and ascorbic acid had strongly inhibitive effects. The Michaelis-Menten constant (K(m)) and maximal reaction velocity (V(max)) of PPO were 0.767 mol/L and 0.519 Ab/min/mL of the crude PPO solution, respectively. PPO was finally purified to homogeneity with a purification factor of 4.41-fold and a recovery of 12.41%. Its molecular weight was 60.4 kDa, indicating that the PPO is a dimer. The data obtained in this research may help to prevent the enzymatic browning of rape flower during its storage and processing.     

电喷雾纳米涂膜工艺优化及其对双孢蘑菇保鲜效果

为了使涂膜技术更有效地应用于果蔬采后保鲜,该文通过电喷雾技术将纳米SiO_2/马铃薯淀粉膜液喷涂在新鲜的双孢蘑菇上,研究了在(4±1)℃贮藏期间双孢蘑菇生理品质的变化,筛选出适于电喷雾涂膜的最佳膜液浓度,且对电喷雾形成涂层的性能(透水率、透O_2率、透CO_2率、水溶性、溶胀度、拉伸强度)和微观结构(scanning electron microscopy,SEM、X-ray diffraction,XRD、fourier transform infrared spectroscopy,FTIR)进行一定的研究。结果表明,适合双孢蘑菇电喷雾技术纳米涂膜保鲜的最佳膜液0配比为纳米SiO_2质量分数0.4%、马铃薯淀粉质量分数4%、甘油质量分数3%,其透水率、透O_2率、透CO_2率分别为514.35、126.84、778.06 g/(m2×d)、拉伸强度24.50 MPa、水溶性54.76%、溶胀度85.75%。电喷雾因液滴带同种电荷,形成的涂层比较均匀,纳米SiO_2分散性更好,分子间作用力较强,且涂层的性能更优。在贮藏保鲜期间电喷雾处理的双孢蘑菇相对普通喷雾处理组能保持较好(P0.05)的感官品质及生理品质,研究结果为电喷雾技术在食用菌采后保鲜的应用上提供参考。