Changes in the content and composition of vitamin E in damp barley stored in airtight bins

The effect of airtight storage on the content and composition of vitamin E was studied in damp barley at 20 and 28% moisture. Airtight storage with an external supply of carbon dioxide was compared with conventional airtight storage with or without an expansion sack. In two additional models, the grain was also treated with 1% ammonia (NH3). The tocopherols and tocotrienols in the grain were analysed using high pressure liquid chromatography with fluorescence detection. The changes in vitamin E during airtight storage were determined by the moisture content of the barley. In barley at 20% moisture, the vitamin E content increased until mid-April and after 10 months the final levels were similar to those at harvest (55–65 mg kg^?1) except in the bin treated wih ammonia. In barley at 28% moisture, vitamin E breakdown processes prevailed from the beginning of airtight storage and led to an unsatisfactory level of this vitamin in the grain. In barley, α-tocotrienol was clearly the dominating isomer. The relative distribution of the isomers in barley at 20% moisture was stable during the airtight storage. For 28% moisture barley in most of the experimental models, the fraction of tocopherol isomers increased at the cost of the tocotrienols. It was concluded that the higher moisture content and a lower pH apparently favoured saturation of the side chains of the trienols. Treatment of barley with 1% ammonia gas resulted in a general decrease in the total vitamin E content and a simultaneous increase in the relative fraction of α-tocotrienol. Therefore, α-tocotrienol appeared to be more resistant to ammonia treatment than are the other isomers. For barley at 20% moisture content, the type of silo arrangement had hardly any effect on the vitamin E concentration or on the proportions of the isomers. For the barley at 28% moisture content, an external supply of CO₂ appeared to have a preservative effect on vitamin E content.     

Odor volatiles associated with microflora in damp ventilated and non-ventilated bin-stored bulk wheat

Western hard red spring wheat, stored at 20 and 25% moisture contents for 10 months during 1985-86, was monitored for biotic and abiotic variables in 10 unheated bins in Winnipeg, Manitoba. The major odor volatiles identified were 3-methyl-1-butanol, 3-octanone and 1-octen-3-ol. The production of these volatiles was associated and correlated with microfloral infection. Ventilation, used for cooling and drying of grain, disrupted microfloral growth patterns and production of volatiles. The highest levels of 3-methyl-1-butanol occurred in 25% moisture content wheat infected with bacteria, Penicillium spp. and Fusarium spp. In non-ventilated (control) bins with 20% moisture content wheat, 3-methyl-1-butanol was correlated with infection by members of the Aspergillus glaucus group and bacteria. In control bins, 1-octen-3-ol production was correlated with infection of wheat of both moisture contents by Penicillium spp. The fungal species, isolated from damp bin-stored wheat and tested for production of odor volatiles on wheat substrate, included Alternaria alternata (Fr.) Keissler, Aspergillus repens (Corda) Saccardo, A. flavus Link ex Fries, A. versicolor (Vuill.) Tiraboschi, Penicillium chrysogenum Thom, P. cyclopium Westling, Fusarium moniliforme Sheldon, F. semitectum (Cooke) Sacc. In the laboratory, fungus-inoculated wheat produced 3-methyl-1-butanol; 3-octanone and 1-octen-3-ol were also produced, but less frequently. Two unidentified bacterial species isolated from damp wheat and inoculated on agar produced 3-methyl-1-butanol.     

Post-harvest storage of corn: effect of beginning moisture content on mycoflora and fumonisin contamination.

The effect of storage on mycoflora profile was monitored bimonthly in 36 corn (Zea mays L.) samples, dividing the same sample into groups dried to 11 and 14% moisture content (1008 analysis). These groups were further subdivided based on the initial total count (moulds and yeasts) up to 10(4) CFU g(-1) (12 samples, range 1.6 x 10(4) to 9.0 x 10(4), mean 3.8 x 10(4) CFU g(-1)) and up to 10(5) CFU g(-1) (24 samples, range 1.0 x 10(5) to 5.0 x 10(5), mean 2.7 x 10(5) CFU g(-1)). In the corn group dried to 11%, the fumonisin content was analysed at the initial stage (freshly harvested) and at the end of 12-month storage. Fusarium spp. and Penicillium spp. prevailed at the freshly harvested stage (100%), maintaining this profile throughout 12 months, in corn dried to both 11 and 14%. Cladosporium spp., Aspergillus spp. and Phoma spp. were also detected at lower frequencies during the storage. Fusarium spp. and the total fungal colony count during 12-month storage carried out with samples dried to 11 or 14% moisture content were statistically evaluated using ANOVA for randomized complete block design. The correlation between storage time and Fusarium spp. and total fungal colony count data was analysed by Pearson's correlation test. There was no difference in Fusarium spp. and total counts in the 10(4) CFU g(-1) initial total count group throughout the storage time (p < 0.05). There was a negative correlation between fungal population and storage time (p < 0.05) in the 10(5) CFU g(-1) initial total count group. Fumonisins were detected in all freshly harvested corn, at a mean concentration of 9.9 +/- 6.0 micro g g(-1) (range 0.74-22.6 micro g g(-)1). These values did not change in the 12-month stored corn (mean of 9.9 +/- 5.8 micro g g(-1), range 0.81-23.7 micro g g(-1)). These post harvest data indicated the importance of moisture content at the crop harvesting/predrying stage to control fungal growth and further fumonisin production.     

PREDICTING THE GERMINATIVE ENERGY OF DORMANT MALTING BARLEY DURING STORAGE

The management of dormant barley stocks for malting requires a method of predicting germinative energy under given conditions during storage. A method of quantifying the relationship between storage temperature and the dormancy period is developed based on probit analysis. The experimental data were obtained using Triumph barley. The conditions covered in the experimental work were 8°C to 38°C storage temperature at 12% moisture content, wet basis. Combined use of the dormancy model with an existing viability model allows the prediction of germinative energy as a function of storage temperature and moisture content given the initial germinative energy and capacity values. The effects of storage temperature on the variation in germination over time of dormant bariey samples with various initial germinative capacities, and storage moisture contents are investigated using the model. The results indicate that storage at moisture contents below 12% give significant increases in the germination level that can be achieved.     

不同储藏条件下玉米真菌多样性研究

研究不同含水率玉米在温度为20、25、303、5℃及相对湿度为70%～80%、80%～90%、≥90%条件下储藏过程中霉菌数量、种群组成、Simpson优势度指数和优势微生物种群变化动态。结果表明:从不同含水率玉米中分离到的优势霉菌主要是青霉属(Penicillium)、曲霉属(Aspergillus)、根霉属(Rhizopus)和镰刀霉属(Fusarium),玉米含水率为10.04%和14.72%时,优势霉菌为青霉属和曲霉属;玉米含水率为19.41%时,优势霉菌为曲霉属中灰绿曲霉和黄曲霉。霉菌多样性特征与玉米的储藏环境有关,温度低且玉米含水率低时,霉菌的多样性大,优势度小;而高含水率玉米的霉菌多样性小,优势度大。含水率和温度对玉米脂肪酸值变化有显著影响,玉米含水率和储藏温度越高,脂肪酸值含量越高。     

Deterioration of shelled oil palm kernels caused by seedborne fungi

Autoclaved oil palm kernels were inoculated with spores of seedborne isolates of either Aspergillus flavus, A. niger, Penicillium chrysogenum, P. janthinellum, Paecilomyces varioti, Syncephalastrum racemosum or Fusarium oxysporum. At 0, 2, 4 and 8 weeks after inoculation, determinations were made of the moisture content, oil, free fatty acids (FFA), sugars and protein nitrogen. The principal biochemical changes induced by these fungi were increases in moisture content and FFA, decreases in total oil and total sugars and a degradation of protein nitrogen. Aspergillus flavus caused the greatest changes, and P. varioti caused the least changes under the moisture conditions of this experiment. The main type of deterioration was hydrolytic rancidity of the oil, resulting in a dark reddish-orange-coloured oil and a discoloration of the kernel meal.     

Effect of gamma irradiation on aflatoxin production in barley

Barley was inoculated with conidia of Aspergillus parasiticus NRRL 2999, and at 0°C was left to equilibrate at three moisture levels: 17, 20 and 25%. Gamma irradiation at five doses, 0, 50, 100, 200 and 400 krad, was applied to the grain either soon after moisture equilibration (3 days after inoculation) or 10 days later (13 days after inoculation). Increasing the radiation dose resulted in decreasing aflatoxin formation, with one exception: 200 krad applied 13 days after inoculation on barley stored at a moisture level of 25% (100% relative humidity) and 25°C led to higher aflatoxin production than at 100 or 50 krad. For the control of aflatoxin contamination in barley, storage at low moisture content appears to be more practical and effective than irradiation.     

The sorption isotherms of maize meal

Summary. The equilibrium moisture contents of the three main grades of South African maize meal over a range of 1.4-90.7% relative humidity (r.h.) were determined at 30°C. It was found that the fat content of maize meal influenced the moisture content at equilibrium, i.e. the higher the fat content, the lower the equilibrium moisture content for a specific relative humidity. Both desorption and adsorption isotherms for maize meal were found to be sigmoid and the effects of hysteresis were encountered in all cases. On prolonged storage mould growth occurred in maize meals held in an atmosphere of 84% r.h. and higher. From the sorption isotherms the maximum r.h. at which maize meal could be stored without the danger of mould contamination could be predicted.     

Comparison of deterioration of rye under two different storage regimes

Deterioration of stored rye samples was studied at different moisture contents and temperatures. Germination, presence of visible and invisible microflora, and free fatty acid values (FAV) were determined for samples at 10.0, 12.5, 15.0 and 17.5% moisture content (wet mass basis) stored at 10, 20, 30 and 40 °C for 16 weeks. Results of deterioration at constant moisture content (case 1) were compared with previously reported results for deterioration under declining moisture content (case 2). Germination rate was almost the same for all the moisture content samples stored at 10 °C for both cases, but a significant decrease was observed at other temperatures with high moisture content. Fatty acid values remained similar in both cases when rye was stored at 10 and 20 °C, whereas at 30 and 40 °C, FAVs of the rye samples in which the moisture content was maintained were high and increased with an increase in temperature and moisture content. Visible mould appeared early in the samples whose moisture content was maintained. Penicillium spp. and Aspergillus glaucus group were the predominant fungal species present in both the cases throughout the study. The rate of deterioration was significantly different between the two cases.     

Moisture sorption isotherm and xerophilic moulds associated with dried cocoyam chips in storage in Nigeria

Extended storage of cocoyams (Colocasia antiquorum and Colocasia esculenta) is achieved in parts of Nigeria by processing them into smoked and dried chips. In this study, cocoyam chips were collected from parts of Nigeria at the end of drying, at various periods of storage and from markets, and analysed for moisture content, moisture sorption characteristics and xerophilic moulds. Moisture content of chips ranged from 7.07 ± 1.1% for freshly dried samples to 16 ± 2.2% for samples stored up to 8 months. Six mould species from four groups of the genus Aspergillus (including five xerophiles) identified as Aspergillus fumigatus, Eurotium repens, Eurotium amstelodami, Eurotium chevalieri and Aspergillus flavus and Aspergillus niger and Mucor sp. were isolated. The variety of moulds increased with storage and moisture content of samples. Moisture sorption in dried chips showed type II sigmoidal behaviour. Wood smoke significantly protected chips from mould colonization, but in cooperation with reduced water activity. Simple and inexpensive storage of freshly dried samples in airtight bags led to prolonged storage of up to 14 months without deterioration.     

Safe storage guidelines for durum wheat

Storage conditions determine the safe storage period for any grain. Safe storage guidelines for durum wheat have not been developed, despite the fact that it is more susceptible to spoilage than other wheat classes. The rates of deterioration of durum wheat samples with 15, 16, 17, 18, 19 and 20% initial moisture content (wet basis) stored at 10, 20, 30 and 40 °C for 12 wk were studied. The grain deterioration parameters including seed germination, moisture content, appearance of visible mould, invisible microflora, free fatty acid value (FAV), and ochratoxin production were monitored at regular intervals. From these results, safe storage guidelines for durum wheat were developed with respect to the moisture content and storage temperature. Germination rates of the samples decreased with an increase in moisture content, temperature and storage period. Visible mould was found in all high moisture samples (17, 18, 19 and 20%) stored at high temperatures. FAV of the samples increased with moisture content and storage time.     

储粮方式对小麦产后减损与质量安全的影响

目的 研究不同储粮条件对小麦储藏期间减损的影响。方法 设置三种不同储藏条件,1#复合精油防霉剂+小型生物储粮仓的储藏条件、2#小型生物储粮仓储藏条件、3#传统储藏条件,分别在小麦入仓0 d、30 d、60 d、90 d、120 d、150 d、180 d取样,考察小麦表面污染真菌、呕吐毒素(DON)、小麦水分、千粒重和不完善粒。结果 共分离出1054株优势真菌,包括851株丝状真菌和203株酵母菌。丝状真菌分别为草酸青霉(Penicillium oxalicum)、黄曲霉(Aspergillusflavus)、黑曲霉(Aspergillus niger)、尖孢镰刀菌(Fusarium oxysporum),串珠镰刀菌(Fusarium verticillioidesS)、绳状蓝状菌(Talaromyces funiculosus)、链格孢菌(Alternaria alternata);酵母菌有粘红酵母(Rhodotorula glutinis)、锁掷酵母(Sporidiobolus pararoseus)和布勒掷孢酵母(Bullera alba)。1#和2#都能有效维持水分含量、千粒重,控制表面真菌和不完善粒变化;3#水分受环境影响变化大,在60d时发生了虫蚀现象,不完善粒显著增加,导致产后损失增加。另外,1# 仓储过程中DON含量降低了72%,2#DON含量变化不大,3#DON含量降低了36%。气味色泽上,2#保持正常,1#在0-60d精油气味大,色泽正常,在180d时气味色泽基本正常。3#由于虫蚀等原因,气味色泽发生了一点改变。结论 用小型生物储粮仓替代传统储粮方式进行小麦储藏,可极大减轻小麦产后储藏期间的损失,保证小麦质量安全,小型生物储粮仓技术在农户等推广应用前景广阔。     

Changes in selected physical property and enzyme activity of rice and barley koji during fermentation and storage

Koji are solid-state fermentation products made by inoculating steamed grains with the spores of fungi, particularly Aspergillus spp. This research was undertaken to identify the fermentation and storage conditions optimal for the production and maintenance of selected hydrolytic enzymes, such as α-amlyase and protease, in koji. Steamed rice and barley were inoculated with 2 × 10 (11) Aspergillus oryzae spores per kilogram of grains and fermented for 118 h in a growth chamber at 28 to 32 °C with controlled relative humidities. Samples were drawn periodically during fermentation and storage at -20, 4, or 32 °C, and α-amylase and protease activity, mold counts, a(w), moisture contents, and pH of collected samples were determined. It was observed that the a(w), moisture contents, and pH of the koji were influenced by the duration of fermentation and temperature of storage. The α-amylase activity of both koji increased as the populations of A. oryzae increased during the exponential growth phase. The enzyme activity of barley koji was significantly higher than that of rice koji, reaching a peak activity of 211.87 or 116.57 U at 46 and 58 h, respectively, into the fermentation process. The enzyme activity in both products started to decrease once the mold culture entered the stationary growth phase. The protease activities of both koji were low and remained relatively stable during fermentation and storage. These results suggest that rice and barley koji can be used as sources of α-amylase and desired enzyme activity can be achieved by controlling the fermentation and storage conditions. PRACTICAL APPLICATION: Amylases and proteases are 2 important hydrolytic enzymes. In the food industry, these enzymes are used to break down starches and proteins while reducing the viscosity of foods. Although amylases and proteases are found in plants and animals, commercial enzymes are often produced using bacteria or molds through solid state fermentation, which is designed to use natural microbial process to produce enzymes in a controlled environment. A properly produced and maintained koji with a high hydrolytic enzyme activity can serve as an important source of the enzymes for the food industry.     

Effect of moisture and temperature on storage changes in lipids and carotenoids of atta (wheat flour)

Effect of moisture and temperature on changes in total carotenoids, fat acidity, free and bound lipids and their composition taking place during storage of atta are reported. At moisture contents of 10.4% and below, increase in fat acidity results mainly from hydrolysis of neutral lipids; phospho- and galactolipids are not hydrolyzed to a significant extent. At moisture level of 11.6% and above both phospho- and galactolipids are degraded to a significant extent. At moisture levels of 12.9% and above mould growth ensues which greatly accelerates the rate of degradation of both polar and non polar lipids. Degradation of carotenoids also increases with increase in storage temperature and moisture content from 9.4 to 16%.     

PRESTORAGE MOISTURE CONTENT AFFECTS COLOR LOSS OF GROUND PAPRIKA (Capsicum annuum L.) UNDER STORAGE

Ground paprika samples from cultivars ‘B-18’; and ‘NuMex Sweet’; were adjusted to different prestorage moisture contents and stored under ambient temperature (19C–24C) and humidity (24–42%). Moisture content, water activity, extractable color, and surface color were determined before storage and then monthly for four months. Prestorage moisture contents equilibrated during storage. At the end of the storage period all samples had about 10% moisture content. Samples with 6% or 9% prestorage moisture content had 92% and 90% extractable color loss, respectively, for ‘B-18’; paprika and 84% and 83% color loss for ‘NuMex Sweet’; paprika, respectively. In contrast, samples stored at higher moisture contents had less color loss. Color loss after four months storage was 53% and 32% for ‘B-18’; and 51% and 30% for ‘NuMex Sweet’; at 15% and 18% prestorage moisture contents, respectively. Surface color was also affected by moisture content.     

Correlation of total ergosterol levels in stored canola with fungal deterioration

Deterioration of canola caused by fungal growth during storage is a problem at moisture contents exceeding 8%. Secondary indicators of fungal growth, such as ergosterol, the main sterol found in fungal cell membranes, offer a way of relating fungal biomass to deterioration. The objective of this research was to determine ergosterol accumulation in stored canola and to correlate it with seed deterioration measured by germination, fungal infection, fat acidity values (FAV), and carbon dioxide production. Total ergosterol levels increased with storage time, temperature, and seed moisture content. Aggressive and destructive fungal species such as Aspergillus candidus and Penicillium spp. contributed more to ergosterol than Eurotium spp. Initial total ergosterol concentrations between 1.46 and 1.67 ppm may be taken as the background levels in sound canola, and levels greater than 2 ppm were related to significant levels of spoilage. Results showed that germination and FAV had a strong correlation with total ergosterol (Spearman rank order correlation coefficients of −0.826 and 0.800, respectively) but the relationship was weaker for CO₂ production (Spearman rank order correlation coefficient of 0.650).     

Investigation on the toxicity of fungi from rootstock snacks

Chicken embryo bioassay was used to monitor the toxicity of extracts from rootstock snack samples during a 210-day storage period. Results show that the relative toxicity values which were initially very low increased significantly as from 120th day (when 32% mortality was recorded) up till the last day when 73% was obtained. Toxicity of extracts from axenic cultures of 12 fungal species isolated from the snack samples was also determined. The strains of Aspergillus chevalieri, Rhizopus nigricans and Rhizopus sp investigated were nontoxic. A. niger, A. flavus, A.fumigatus, Penicillium chrysogenum, A. parasiticus, P. citrinum, A. ochraceus, Fusarium monifilorme and A. candidus were found to be toxic in decreasing order of potency as recorded after 30 days of growth at room temperature on substrate of 0.90 water activity level. Trends in the moisture content levels, pH and the incidence of fungal growth on the snack samples were also studied. Results suggest that storage for a period not exceeding 90 days and maintenance of safe moisture level would control mould growth and the associated mycotoxins in the snack.     

Kinetics of mould growth in the stored barley ecosystem contaminated with Aspergillus westerdijkiae,Penicillium viridicatum and Fusarium poae at 23–30 °C

BACKGROUND: Owing to the lack of a rapid method for determining fungi on cereals, the best way to enhance the safety and nutritive value of stored grain is to develop prognostic tools based on the relationship between easily measurable online parameters, e.g. water activity (a_w) and temperature (t) of grain, and fungal growth. This study examined the effect of unfavourable temperature (23 and 30 °C) and humidity (0.80–0.94 a_w) storage conditions on mould growth in the stored barley ecosystem with its adverse microbiological state provided by contamination with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae. RESULTS: Among the applied storage parameters, a_w turned out to be the main factor affecting mould development. The longest lag phase and period of fungal activation were observed for grain with 0.80 a_w, which was not threatened with fungal development for at least 30 days. However, in grain with 0.92 and 0.94 a_w, fungal activation occurred within 24–48 h. CONCLUSION: The obtained data and the identification of critical points in mould growth may be used to develop a control system for the postharvest preservation of barley based on a_w and temperature of grain, which are easy to measure in practice. © 2012 Society of Chemical Industry     

基于监测过氧化氢酶活性对储藏玉米AFB1污染的早期预警

早期预警是防控储藏玉米污染黄曲霉毒素B1(AFB_1)的重要手段。将不同含水量的玉米置于各种温度环境下进行储藏试验,研究过氧化氢酶活性变化与玉米污染黄曲霉毒素B1(AFB_1)的关系,结果表明,两者数据变化的趋势一致,AFB_1是过氧化氢酶活性的二次曲线函数(相关性系数大于0.95)。储藏温度和玉米含水量等条件可改变所含霉菌产生AFB_1和升高过氧化氢酶活性的速度,但不影响数值变化的趋势。在各种储藏条件下,过氧化氢酶活性变化可比玉米中AFB_1含量显著变化的起始点提前4~21d。因此,借助检测过氧化氢酶活性的方法可以早期预警储藏玉米污染AFB_1。