基于高通量测序探究东北粳稻储藏期间真菌群落的演替

为探究不同初始水分的东北粳稻在模拟实仓环境储藏的条件下,稻谷中真菌群落随储藏时间的演替变化。选取水分在14.50%~15.50%的稻谷HW和13.50%~14.50%稻谷LW,进入模拟储藏实验。结果表明,在第一和第二储藏期高水分稻谷HW水分含量由15.50%降低至15.09%,低水分稻谷LW水分含量由14.21%降低至13.59%,直至第三储藏期保持平稳。基于可操作性分类单元（Operational Taxonmic Units,OTUs）的物种分类分析,两种水分的稻谷真菌群落经历了不同的演替变化。高水分稻谷在每个储藏期,真菌群落都发生了明显演替,稻瘟病菌（Magnaporthe_grisea）、金黄色蝶形担孢酵母（Papiliotrema_aurea）、弯孢菌（Curvularia_inaequalis）、黑孢霉（Neosetophoma_samararum）、汉纳酵母菌（Hannaella_sinensis）在储存结束时成为了最终的优势菌种。低水分稻谷在第二储藏期真菌群落发生明显演替,优势菌种为弯孢菌（Curvularia_inaequalis）、汉纳酵母菌（Hannaella_sinensis）、Hannaella_zeae。     

真菌及昆虫在储藏小麦中生长产生CO_2气体的特点

在各种温、湿度条件下对小麦储藏期间真菌和昆虫活动产生二氧化碳气体(CO2)进行监测,研究可用于判断小麦储藏安全性的方法。试验结果表明,储粮温度对处于生长状态的真菌产CO2速率影响最大,从20℃升高到25℃,产CO2速率可提高10倍。在安全水分小麦中,昆虫是产CO2的主要类群,对高水分小麦,真菌是产CO2的主体。在产CO2特性方面,昆虫密度与产CO2量具线性关系(r0.99),而真菌产CO2呈明显的加速现象,在储藏初期带菌量没有显著增加(p0.05)时,产气速率已提高5.96倍。在大型粮仓储藏中的试验也表明,昆虫的产气量恒定,粮堆4 m深度昆虫活动部位25 d的CO2浓度变化幅度为13%,而离霉变点0.5 m的CO2浓度变化高达37倍。因此,利用检测CO2气体浓度变化的方法可以灵敏地发现小麦储藏中昆虫和真菌的危害活动。     

小麦储藏安全水分的研究

对储粮安全水分、真菌生长临界水分、储粮水分迁移进行了研究。研究发现,在常规条件下,储粮安全水分(MC)与真菌生长临界水分(mc)和储粮中水分迁移最大增量值(Δmc)有关,当MC+Δmc≤mc时,储粮是安全的,否则,是不安全的。并由此可得出储粮安全水分临界值MC=mc-Δmc。通过这个理论计算公式,以我国北方小麦储藏为例,进行了我国北方小麦储藏安全水分的初步研究。试验结果表明,小麦真菌生长临界水分为14.0%,水分迁移最大增量值为1.0%,我国北方小麦储藏安全水分临界值在13.0%左右。     

应用高通量测序技术检测小麦储藏过程中真菌群落的变化

通过高通量测序技术研究仓储小麦中真菌群落的变化规律及影响因素,为小麦仓储条件优化提供参考。结果表明,仓储小麦中真菌污染以链格孢霉、曲霉、枝孢霉为主,其中曲霉属测得11个种,是物种多样性最高的属。结果表明,小麦储藏时间可能对其中真菌群落有较大的影响,储存1、2、3 a的小麦真菌群落有各自的特征真菌。小麦在仓库中的储藏方位可能与其中的真菌群落关系较小。储存深度对小麦真菌群落有影响,其中粪壳菌纲的微生物随着储藏深度的增加而丰度变低。河南和黑龙江两地的仓储小麦真菌群落差异较大。本研究可以为仓储小麦中真菌群落的发生演变模型的建立提供基础数据支持,为仓储小麦真菌控制提供可行方案。     

稳定方法对小麦胚理化特性及储藏性能的影响

分别采用微波法、高压气蒸法、常压气蒸法和干热法对小麦胚进行稳定化处理,并与未经处理的样品在色泽、气味、水分及其提油率、蛋白溶解性、储藏性能等进行比较研究.结果表明:与其他稳定化方法相比,微波稳定化处理的小麦胚保持原有色泽和气味,达到同样水分含量,微波处理的时间显著较短,温升较慢,但出油率较高,且在储藏期间脂肪酸值变化率较小.     

两种装具对籼稻储藏损失影响的对比研究

对三节式彩钢板组合仓(组合仓)和聚乙烯塑料仓(PE仓)储藏籼稻1年的重量损失和品质变化的影响进行了研究。结果表明,组合式粮仓的储粮平均损失率为3.10%, PE仓储粮平均损失率为0.5%。PE仓相较于组合仓,所储籼稻的霉变、虫蚀,水分损失、脂肪酸值、蛋白质含量、直链淀粉含量等品质劣变指标比较小,是一种更好的农户储粮装具。     

小麦储藏危害真菌生长规律的研究

采用真菌孢子计数法,对不同含水量的小麦在储藏期间,危害真菌生长的规律进行了研究.结果表明:在30℃,13.3%、14.2%、15.7%、16.4%四个水分的小麦样品,除13.3%水分储藏90 d未检出有危害真菌生长外,14.2%水分储藏80 d时,可检出有真菌生长迹象,但生长很慢.15.7%和16.4%两个水分,储藏20 d时,检出有真菌生长,这些真菌初期生长速度较快,当达到一定的值时,生长逐步减缓,整个生长呈动态变化过程,即:孢子-菌丝-孢子;经初步鉴定表明:在本试验中以灰绿曲霉生长为主,另外还有少量的白曲霉和青霉.整个试验期间样品的水分变化幅度为0.3%～0.9%,温度变化幅度为0.3～1.1℃,其变化大小与危害真菌生长有明显的关系;本方法与感染粒法比较,两者研究的结果具有良好的相关性.     

不同储藏条件下粳稻谷脂肪酸值及气味变化研究

将不同水分(12.5％、13.5％、14.5％、15.5％)的粳稻谷分别置于不同温度(15、20、25、30℃)的恒温箱中储藏4个月,每30 d检测1次脂肪酸值和气味.结果表明:随着储藏时间的延长脂肪酸值先增加继而有下降趋势,温度和水分越高,粳稻谷的脂肪酸值越大.水分为15.5％的粳稻谷在30、25、20、15℃条件下储藏60 d后,脂肪酸值(mgKOH/100 g)上升至47.36、42.60、36.47、32.77;25℃条件下,水分为15.5％、14.5％、13.5％、12.5％的粳稻谷储藏90 d后脂肪酸值分别上升至44.79、42.11、42.47、39.47.水分为14.5％的粳稻谷在30、25、20、15℃条件下储藏120 d后,气味值分别升高了1.69、1.56、1.03、1.21;30℃条件下,水分为15.5％、14.5％、13.5％、12.5％的粳稻谷储藏120 d后气味值分别升高至1.79、1.60、1.28和1.02.脂肪酸值与气味值回归方程为y=-1.522 +0.144x-0.002x2,R =0.917,R2 =0.841.     

小麦产毒病原菌及其毒素防控的研究进展

小麦是全球第二大粮食作物,每年因病害造成小麦严重减产,品质下降。一些病原菌还能够产生真菌毒素,进一步危害小麦及其制品的质量安全,对人畜健康造成巨大危害。由镰刀菌引起的小麦赤霉病是我国最主要的小麦病害之一,由交链孢引起的小麦黑胚病也备受关注。这2种真菌既能引起小麦病害,又能产生真菌毒素,故称之为产毒病害。镰刀菌产生的脱氧雪腐镰刀菌烯醇(deoxynivalenol,DON)、玉米赤霉烯酮(zearalenone,ZEN)、伏马菌素等和交链孢产生的交链孢酚(alternariol,AOH)、交链孢酚单甲醚(alternariol monomethyl ether,AME)和细交链格孢酮酸(tenuazonic acid,Te A)等是2类病原菌产生的主要真菌毒素。本文综述了能引起小麦产毒病害的镰刀菌和交链孢的特点、真菌毒素以及病害和毒素的防控技术,尤其是2类病原菌引起的小麦病害和真菌毒素的防控。这将为后期防治小麦产毒病害及控制毒素产生的研究提供有利参考。     

农户小麦储藏品质评价指标研究

为了探讨农户储粮的品质评价指标,为农户储藏小麦的品质检验与控制提供指导,对取自河南省小麦主产区储藏的3个年份小麦样品质量指标以及储藏品质指标进行测定,筛选能够明显反映出农户小麦储藏品质变化的指标.结果表明,随着储藏时间的延长,发芽率、面筋吸水率作为快速判定农户小麦质量及品质变化的指标灵敏性不高,霉变粒、不完善粒和降落数值随时间变化较大,且与储藏时间呈极显著相关,相关系数分别为0.566、0.837和0.545,在各个指标中尤其是虫蚀率与储藏时间呈极显著相关(r=0.960),虫蚀率变化最为灵敏,且不受其他测定因素的影响,可操作性强,可以直接用来评价农户小麦储藏品质.     

优质籼米地下仓储藏过程中品质变化

为探索成品粮绿色、安全的储藏方法,在南方高温高湿地区,利用地下仓储藏黄花粘和籼优998两种优质籼米,定期检测水分、碎米总量、小碎米率、垩白粒率、黄粒米、直链淀粉、品尝评分值、色泽气味、不完善率、害虫虫口密度等指标。实验结果显示,实验期间,大米水分呈小幅下降;2种大米不生虫时间长达13个月;小碎米率、色泽气味等指标无显著性变化;碎米总量、黄粒米、不完善粒含量小幅增加,直链淀粉含量逐渐增加,但均未导致大米质量等级下降;垩白粒率显著增加,品尝评分值显著下降,且均造成大米质量定等下降。根据国家标准《大米》的规定,籼优998于储藏3个月后,质量定等由二级降为三级,储藏6个月后,已不属于优质籼米,黄花粘于实验结束后仍为优质籼米三级。说明地下仓具有良好的保湿、保鲜和害虫抑制效果,优质籼米耐储性能与储藏条件和品种均相关。     

Estimating mycotoxin contents of Fusarium-damaged winter wheat kernels

Winter wheat (Triticum aestivum L., cultivars Ritmo and Dekan) grain was sampled in Northern Germany between 2001 and 2006. Kernels damaged by fungi of the genus Fusarium were separated from sound grain by visual assessment. Samples containing 0%, 20%, 40%, 60%, 80% and 100% of Fusarium-damaged kernels were compiled and analyzed for the Fusarium type B trichothecenes deoxynivalenol (DON, 2001-2006), nivalenol (NIV, 2006), 3-acetyl-deoxynivalenol (3AcDON, 2006) and 15-acetyl-deoxynivalenol (15AcDON, 2006). The relationship between mycotoxin contents and the percentage of Fusarium-damaged kernels was calculated for each lot of grain. Apart from one exception, relationships between the percentage of Fusarium-damaged kernels and NIV, 3AcDON or 15AcDON were non-significant. In contrast, close relationships between the percentage of Fusarium-damaged kernels and the DON content were observed (r(2)=0.93-0.99). The y-axis intercepts were not significantly different from zero, but the DON content of the damaged kernels varied by a factor of 11.59 between years and by a factor of 1.87 between cultivars. Fusarium-damaged kernels contained between 0.21 and 2.39 microg DON kernel(-1). The overall average DON content of a Fusarium-damaged wheat kernel was 1.29 +/- 0.11 microg. The DON content of diseased kernels was affected by environment and wheat genotype but not by genotype x environment interaction. On average, Fusarium-damaged kernels contained 9.7-fold more DON than 15AcDON, 19.5-fold more DON than NIV, and 26.9-fold more DON than 3AcDON. 3AcDON and 15AcDON contents per wheat kernel were not significantly different between cultivars. On average, 4.27% of Fusarium-damaged kernels were sufficient to reach the 1.25 mg DON kg(-1) grain limit for unprocessed cereals in the EU. Given the low percentages of Fusarium-damaged kernels that are equivalent to current legal DON limits, grading accuracies >96% would be needed when using automatic grading systems for separating sound from damaged kernels.     

Quality changes in macadamia kernel between harvest and farm-gate

BACKGROUND: Macadamia integrifolia, Macadamia tetraphylla and their hybrids are cultivated for their edible kernels. After harvest, nuts‐in‐shell are partially dried on‐farm and sorted to eliminate poor‐quality kernels before consignment to a processor. During these operations, kernel quality may be lost. In this study, macadamia nuts‐in‐shell were sampled at five points of an on‐farm postharvest handling chain from dehusking to the final storage silo to assess quality loss prior to consignment. Shoulder damage, weight of pieces and unsound kernel were assessed for raw kernels, and colour, mottled colour and surface damage for roasted kernels. RESULTS: Shoulder damage, weight of pieces and unsound kernel for raw kernels increased significantly between the dehusker and the final silo. Roasted kernels displayed a significant increase in dark colour, mottled colour and surface damage during on‐farm handling. CONCLUSION: Significant loss of macadamia kernel quality occurred on a commercial farm during sorting and storage of nuts‐in‐shell before nuts were consigned to a processor. Nuts‐in‐shell should be dried as quickly as possible and on‐farm handling minimised to maintain optimum kernel quality. Copyright © 2010 Society of Chemical Industry     

Impact of storage environment on the efficacy of hermetic storage bags

Small hermetic bags (50 and 100 kg capacities) used by smallholder farmers in several African countries have proven to be a low-cost solution for preventing storage losses due to insects. The complexity of postharvest practices and the need for ideal drying conditions, especially in the Sub-Sahara, has led to questions about the efficacy of the hermetic bags for controlling spoilage by fungi and the potential for mycotoxin accumulation. This study compared the effects of environmental temperature and relative humidity at two locations (Indiana and Arkansas) on dry maize (14% moisture content) in woven polypropylene bags and Purdue Improved Crop Storage (PICS) hermetic bags. Temperature and relative humidity data loggers placed in the middle of each bag provided profiles of environmental influences on stored grain at the two locations. The results indicated that the PICS bags prevented moisture penetration over the three-month storage period. In contrast, maize in the woven bags increased in moisture content. For both bag types, no evidence was obtained indicating the spread of Aspergillus flavus from colonized maize to adjacent non-colonized maize. However, other storage fungi did increase during storage. The number of infected kernels did not increase in the PICS bags, but the numbers in the woven bags increased significantly. The warmer environment in Arkansas resulted in significantly higher insect populations in the woven bags than in Indiana. Insects in the PICS bags remained low at both locations. This study demonstrates that the PICS hermetic bags are effective at blocking the effects of external humidity fluctuations as well as the spread of fungi to non-infected kernels.     

河北省2010年至2019年小麦质量监测数据统计分析

为了给小麦收储企业和加工企业提供河北省小麦质量信息,对合理利用当地小麦资源提供技术依据,对2010年至2019年河北省小麦主产区的新收获小麦进行容重、千粒重、不完善粒含量、生芽粒含量、水分、硬度指数、降落数值、湿面筋含量以及蛋白质含量等品质质量指标的分析,从各检测指标的年度变化、各市检测指标平均值比较和检测指标优选比较三个方面分析河北省近十年小麦的质量情况。结果表明：除2013年、2018年外均为正常年景。2013年的小麦质量是十年之中最差的,小麦的容重、千粒重、降落数值均处于十年中的最低值,不完善粒含量及生芽粒含量、水分则处于十年中的最高值。在近十年的数据中,辛集市的小麦在高容重、高千粒重、低不完善粒含量、高硬度指数方面上都有明显的比较优势,另外邯郸市、邢台市、石家庄市的小麦在高容重方面有着明显的比较优势。     

热烫前处理对鲜食玉米贮藏过程中保鲜品质的影响

由于鲜食玉米在贮藏期间品质会不断下降,本文利用热烫对鲜食玉米进行前处理,研究其对贮藏期间品质的影响。对鲜食玉米先进行热烫,然后用复合生物保鲜剂进行保鲜,分析含水量、质量损失率、TPA指标、气味与感官品质等,研究贮藏期间鲜食玉米的品质变化。结果表明,热烫前处理的鲜食玉米在贮藏期间,水分含量显著(p<0.05)高于对照,热烫处理可有效抑制鲜食玉米水分散失。热烫处理的鲜食玉米在贮藏0~10 d时,质量损失率略低于对照,30 d时高于对照2.2%,但差异不显著(p>0.05)。热烫处理鲜食玉米的弹性、粘性及回复性与对照差异不显著;而内聚性显著高于对照(p<0.05),硬度、胶粘性和咀嚼性均极显著高于对照(p<0.01)。热烫处理的鲜食玉米气味变化较小。热烫处理对鲜食玉米的保鲜效果较好,能较好保持色、香、味等感官品质。     

不同处理对小麦储藏品质影响的研究

为了进一步加深对小麦贮藏过程的了解,使品质检测数据相对稳定,较系统地分析了不同储存条件对小麦陈化的影响。测定水分含量、发芽率、酸度、脂肪酸值、过氧化氢酶活性、色泽等指标变化情况,讨论了不同储藏条件对小麦品质指标变化的影响。结果表明:真空处理可以很好地抑制氧化分解作用,防止小麦储藏过程中脂肪酸值、酸度的升高,提高小麦的营养价值和商业价值。且以0℃条件下真空处理的小麦储藏品质最佳。     

Effect of harvest time and storage conditions on almond kernel oil and sugar composition

The effect of storage for 6 months at 5 °C (80% RH) versus 20 °C (60% RH) of shelled versus in‐shell almonds was studied on early versus late harvested nuts from ‘Ferragnes’ and ‘Texas’ trees. Kernel quality characteristics, oil composition and sugar composition were determined initially and after 6 months of storage. Early harvested almonds had similar kernel weight to but higher moisture content than late harvested almonds after 6 months of storage. Early harvested almonds also had similar oil quality (based on ultraviolet absorption coefficient measurements) and oil composition but lower sugar content and modified sugar composition compared with late harvested almonds. Storage of shelled almonds resulted in kernels with higher oil content, better oil quality, similar oil composition, similar sugar content and some modifications in sugar composition compared with in‐shell stored almonds. Finally, storage for 6 months at either 5 or 20 °C resulted in lower moisture content, higher oil content, similar oil quality and composition, similar sugar content and some modifications in sugar composition compared with freshly harvested almonds. Almonds stored at 5 °C retained higher kernel weight and moisture content than almonds stored at 20 °C. © 2003 Society of Chemical Industry     

Estimating deoxynivalenol contents of wheat samples containing different levels of Fusarium-damaged kernels by diffuse reflectance spectrometry and partial least square regression

Fusarium head blight is a fungal disease causing yield losses and mycotoxin contamination in wheat and other cereals. Wheat kernels (cultivar Ritmo) were sampled in 2001, 2002, 2003, and 2006 and Fusarium-damaged kernels were separated from sound grain based on visual assessment. Subsequently, grain lots containing 0, 20, 40, 60, 80, and 100% of damaged kernels were compiled. Each lot was split and the spectrometric reflectance (wavelengths 350-2500 nm) was measured using subgroup one, while the concentration of the mycotoxin deoxynivalenol (DON) was determined by high-performance liquid chromatography in subgroup two. DON concentrations in batches classified as sound were not significantly different from 0. Estimating DON contents from the percentage of Fusarium-damaged kernels was impeded by vast variability, resulting in a coefficient of determination of 0.49. Using spectrometric data subjected to partial least square regression allowed estimating DON contents with higher accuracy, in particular at elevated percentages of damaged kernels. The coefficient of determination was 0.84 for the relationship between DON contents estimated based on spectrometric data and the DON contents measured. The intercept of a regression line fitted through a plot of estimated versus measured DON contents was 0.89 ± 3.61 mg/kg. Since intercept + standard error was larger than the actual legal limit (1.25 mg DON per kg dry grain in the European Union), the spectrometric procedure was still not precise enough to allow a reliable separation of grain samples with DON contents below 1.25 mg/kg from samples with DON contents above the limit. However, spectrometric data also allowed estimating the DON content of the average damaged kernel within a given lot composed of sound and damaged kernels, which is probably the reason for the reduction of the fraction of unexplained variance by 35% compared to the visual approach and illustrates that spectrometric approaches can make a contribution to reducing DON contents of wheat grain.     

Growth inhibition of Fusarium graminearum and reduction of deoxynivalenol production in wheat grain by bacillomycin D

Fusarium graminearum causes Fusarium head blight, which leads to the quality and yield loss of wheat. In the present work, the inhibition effects of bacillomycin D (BD) on the growth of F. graminearum and reduction of deoxynivalenol (DON) production in wheat grain storage were investigated. The hyphal growth and sporulation of F. graminearum were restrained dramatically in the presence of 75 μg/mL BD, and the inhibition rate reached to 94.6% and 97.5%, respectively. Ultrastructural observation of the hyphae showed BD caused stripping of F. graminearum hyphal surface and destroying of the cellular structure. Furthermore, BD could lower the free fatty acid value and total antioxidant capacity and delay the decline of wheat quality, then exhibit an effective protection for wheat infection by F. graminearum. BD could effectively inhibit mold growth and DON production during wheat seeds storage, thus enhancing the quality and shelf life of the kernel. The addition of BD (75 μg/g wheat) remarkably inhibited the amount of F. graminearum growth, and reduced the DON production to 47.5–71.5%. These results indicated that BD might be a promising natural and effective fungicide, and would have potential for reducing mycotoxins in food and feed.