Safe storage time of high moisture wheat

Deterioration rates were determined for 15-19% moisture content (m.c., wet basis) wheat (Triticum aestivum L. cv. 'Barrie') stored at constant temperatures or with a step decrease in storage temperatures. Deterioration rates were determined by measuring germination capacity of the grain and respiration rates of grain and microorganisms. Safe storage time was defined as the time for germination to decrease to 90%. Safe storage times of 19% m.c. wheat stored at constant temperatures ranged from 2.5 d at 30 and 35 degrees C to 37 d at 10 degrees C. Deterioration rates of 19% m.c. wheat stored with a step decrease in storage temperatures (35-25, 30-20, 25-20, and 20-15 degrees C) were determined and safe storage times were satisfactorily predicted. Safe storage times of 17% m.c. wheat were 5, 7, and 15 d at 35, 30, and 25 degrees C, respectively. Respiration rates and germination percentages of 15 and 16% m.c. wheat stored at 25 degrees C remained constant for 70 d. The respiration rates of 17-19% m.c. wheat at 25 degrees C increased while the germination percentages decreased with storage time. Germination dropped from 98 to 92-89% when the dry matter losses were about 0.05% and visible mould occurred when the dry matter losses were about 0.1% in 17-19% m.c. wheat. Safe storage times of 17% m.c. wheat stored at 35-25 degrees C were compared with those determined in similar previous work with cultivars 'Domain' and 'Katepwa'. 'Domain' had the longest and 'Barrie' had the shortest storage times.     

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.     

A comparison of the functional characteristics of wheat stored as grain with wheat stored in spike form

In this study, wheat grain and wheat spike with 12%, 14% and 16% moisture content were stored at 10, 20 and 30 °C for 0, 3, 6 and 9 months. After storage, wheat samples were investigated for hectolitre weight, gluten content, Zeleny sedimentation volume, enzyme activity, acidity, phytic acid and L colour value. Storage of wheat at different storage forms (spike and grain) and storage conditions showed considerable changes in grain quality. In general, the storage period of 3 months positively affected wheat quality. However, hectolitre weight, gluten, Zeleny sedimentation, enzyme activity, acidity and colour of wheat got worse at storage periods beyond 3 months. Hectolitre weight, wet and dry gluten, Zeleny sedimentation, phytic acid content and L Colour value of wheat stored in both spike and grain form significantly decreased during storage. However, the increase in grain moisture content, storage time and temperature resulted in significant increase in total titratable acidity and falling number values of wheat. Falling Number and phytic acid values of wheat stored in spike form were generally lower than wheat stored in grain form. Storage in spike form had a positive effect on especially wet gluten content of wheat stored at non-optimal storage conditions such as high grain moisture content and high temperature. Wet gluten of wheat stored in spike form was higher than that of wheat stored grain form after storage at 30 °C for 6 and 9 months. Wheat stored in spike form is more resistant than wheat stored in grain form against adverse storage conditions such as high moisture content and temperature and longer storage time.     

Quality changes in 12% moisture content canola stored in silo bags under Canadian Prairie conditions

A study was conducted for two storage years (2011–12 and 2013–14) to determine the changes in grain quality while storing 12% moisture content (m.c., wet basis) canola seeds in silo bags under Canadian Prairie conditions. Canola seeds were stored in three silo bags (67 tonnes per bag) and unloaded at three different times (one bag at a time) which represent 20 weeks of storage (unloaded in late winter), 28 weeks of storage (unloaded in spring) and 40 weeks of storage (unloaded after summer storage). Canola seed quality parameters (germination, free fatty acid value (FAV), and moisture content), and intergranular composition (CO₂ and O₂ levels) at different locations in silo bags were analysed every two weeks. Temperature of canola seeds at various locations in the silo bag was recorded every 30 min. The germination of canola seeds at most parts of the silo bags stayed above a safe level up to late winter (20 weeks of storage). At the top layer of the silo bags, germination of canola seeds decreased to below 30% during summer storage (after 40 weeks of storage). Moisture content of canola seeds increased at the top layer in both storage years. The FAV values remained at safe levels until 20 weeks of storage, and increased more than two times the initial values after summer storage. The commercial grades after first, second and third unloading (after 20, 28 and 40 weeks of storage) were Grade 1, Grade 2 and Feed Grade, respectively, in year 1. Whereas for year 2, these were Grade 1, Grade 1 and Grade 2 after first, second and third unloading, respectively. The grain quality analysis and commercial grading results indicated that ambient temperature had a major role in quality of canola during storage.     

主要粮食品种储藏期间霉菌活动特性研究

研究了稻谷、玉米和小麦在25℃,相对湿度分别为75%、85%和95%储藏,以及在高于安全水分2%的相似水活度条件下储藏期间霉菌的活动特性.结果表明,小麦最易出现霉菌生长活动,稻谷的抗霉菌生长作用最强,玉米介于小麦和稻谷之间;其中85%相对湿度下储藏至28 d,小麦的微生物活性值升高了475 u,分别是稻谷和玉米同期升高值的5.6和3.5倍.储粮中霉菌活动特性的不同表现与各粮种的吸湿性能及粮粒外皮(颖壳或种皮)的霉菌可生长性差异有关,但将相同霉菌活动强度的储粮样品作相关品质指标的检测,发现小麦的黏度、发芽率变化不明显,而玉米和稻谷的脂肪酸值和发芽率则有较大的变化.因此,对于储藏品质较稳定但易滋长霉菌的小麦应该重点关注霉菌活动的状况,仅仅监测品质指标变化难以准确判断储藏的安全性和粮食相关的食品安全性.     

Efficacy of sensor assisted vacuum hermetic storage against chemical fumigated wheat

Alternatives to chemical fumigation, are being explored as the popular fumigants like methyl bromide and phosphine are being phased out for their ozone depleting nature and insect resistance, respectively. Vacuum hermetic storage has potential for storage of agricultural durable commodities without fumigants and can eliminate 99% of insect infestation. In present research, the vacuum hermetic storage was tested in field with assistance of sensors and compared with the conventional phosphine fumigated storage by grain quality assessment and interstitial atmosphere for six months. Relative humidity of the hermetic bags remained below 25%, whereas temperature followed the same pattern as of the ambient. Germination percentage, thousand kernel weight and besatz content did not change significantly (p > 0.05), whereas mould count and moisture content reduced over the storage time compared wheat stored in metal bin.     

Impact of moisture content and maize weevils on maize quality during hermetic and non-hermetic storage

The objective of this study was to determine the impact of moisture content and Sitophilus zeamais Motschulsky on maize quality during hermetic and non-hermetic storage conditions. Commercial Channel 211-97 hybrid maize kernels were conditioned to 14, 16, 18, and 20% moisture content (wet basis), and then three replications of 300 g of maize grain were stored in glass jars or triple Ziploc^® slider 66-μm(2.6-mil) polyethylene bags at four conditions: hermetic with weevils, hermetic no-weevils, non-hermetic with weevils, non-hermetic no-weevils. All jars and bags were stored in an environmental chamber at 27 °C and 70% relative humidity for either 30 or 60 d. At the end of each storage period, jars and bags were assessed for visual mold growth, mycotoxin levels, gas concentrations, pH level, the numbers of live and dead S. zeamais, and maize moisture content. The maize stored in non-hermetic conditions with weevils at 18 and 20% exhibited high levels of mold growth and aflatoxin contamination (>150 ppb). Conversely, very little mold growth was observed in maize stored in hermetic, and no aflatoxins were detected in any moisture level. CO₂ increased and O₂ gradually decreased as storage time increased for maize stored in hermetic conditions (with or without weevils) in all moisture level. No significant difference in pH was observed in any storage conditions (P < 0.05). Total mortality (100%) of S. zeamais was observed in all hermetically stored samples at the end of 60 days storage. Moisture content for hermetically stored maize was relatively constant. A positive correlation between moisture content and storage time was observed for maize stored in non-hermetic with weevils (r = 0.96, P < 0.05). The results indicate that moisture content and the number of S. zeamais weevils plays a significant role in maize storage, both under hermetic and non-hermetic conditions.     

A systemic approach to qualitative changes in the stored-wheat ecosystem: Prediction of deterioration risks in unsafe storage conditions in relation to relative humidity level, infestation by Sitophilus oryzae (L.), and wheat variety

A multidimensional laboratory trial was carried out to identify the primary causes of changes in quality traits in the stored-grain ecosystem to reveal critical storage condition boundaries that may endanger grain quality retention. Qualitative criteria were followed on grain batches from 3 wheat varieties which were stored for 160 d at temperature of 22-23 °C, at two different relative humidities, and with or without infestation by the rice weevil Sitophilus oryzae, to build a multivariate data matrix. The interactions between biotic deteriorative factors and qualitative trait changes were explored through a principal component analysis (PCA). From the Pearson’s product moment correlation matrix, it was observed that the variables that correlated significantly with insect and fungal species dynamics were: moisture content, hL mass, seed viability, and fat acidity of extracted whole flour. Four factors explained the major part of the variance: storage duration, moisture content, hidden insect infestation density, and fungal contamination level. The rate of increase of the insect population was significantly different between varieties. PCA revealed that the significant difference in qualitative deterioration pattern observed between the three varieties was not related to their hardness but rather to a different relationship between the grain and relative humidity. Germination rate was the first quality factor to decline during the storage period. The technological properties of flour extracted from each variety were not affected before insect population density exceeded 1000 adult insects per kg. The rate of qualitative changes induced by the biotic deterioration factors was processed into a “biodeterioration susceptibility index” (BSI) according to the safe storage time assessed in the present study. This index may be used in IPM approaches to predict the susceptibility of a particular wheat variety to insect and fungal damage during long-term storage.     

Dough characteristics of wheat flour milled from wheat grains stored in spike form

This study compares the effects of storage form (grain and spike) of wheat as well as grain moisture content (12%, 14% and 16%), storage time (0, 3, 6 and 9 months) and temperature (10, 20 and 30 °C) on rheological (farinograph and extensograph) characteristics of dough obtained from stored wheat. While water absorption, stability and degree of softening of wheat stored in spike form were 61.2%, 15.8 min and 25.9 Brabender unit (BU), these values of wheat stored in grain form were 60.8%, 14.1 and 29.1 BU, respectively. Resistance to extension and dough energy of wheat stored in grain form were significantly higher than those of wheat stored in spike form, while extensibility was significantly lower. Storage in spike form had a positive effect on all farinograph and extensograph characteristics of wheat stored under nonoptimal storage conditions such as high grain moisture content, high temperature and long storage time.     

A new method to rapidly detect rusty grain beetle,Cryptolestes ferrugineus (Stephens), in stored grain

Information on insect infestation inside stored grain bulks is required for safe grain storage. A new method to rapidly detect both adults and larvae of Cryptolestes ferrugineus (Stephens) in grain was developed based on the principle of microwave heating and insect behaviour under elevated temperature. The designed apparatus and processing procedure were tested to extract both the adults and larvae inside wheat with 14%, 16% and 18% moisture contents by using a domestic microwave oven (referred to as the microwave method). The recovery percentage of the introduced insects associated with the microwave method was compared with that of the Berlese funnel method (810 cm³ wheat in a funnel under an incandescent light bulb). The microwave method recovered 97.8% of introduced adults, while 90.6% of adults were recovered by the Berlese funnel method. The recovery percentage of the larvae inside marked wheat kernels was 83.3 ± 3.3% with the microwave method and less than 27% with the Berlese funnel method. There was no significant difference in extraction percentage between old and young larvae when the microwave method was used. The moisture content of the treated grain did not significantly influence the extraction percentage of the pest insect. The total processing time of the microwave method was less than 30 min compared to 6 h required for the Berlese funnel method.     

Determination of safe storage moisture content of soybean expeller by means of sorption isotherms and product respiration

Soybean expeller (SBE) is rich in protein and has a relatively high and variable oil composition (7–15%). With the increasing use of the SBE for animal nutrition there arose a need for understanding the quality deterioration during storage. The goal of this research was to determine the storability of SBE by developing a model for predicting its equilibrium moisture content (EMC), using the EMC model to determine its safe storage moisture content (SSMC), and by measuring dry matter loss (DML) for SBE incubated at 10 °C and 20 °C for 46 days. Samples of SBE with different residual oil contents were collected and an EMC experiment was carried out to determine the sorption isotherms at 65, 70, 75 and 80% RH; at 10 and 20 °C for samples with 6.2, 9.6 and 15.3% oil content. A second set of samples was used for determining the respiration rate at 20 °C. The Enhanced Halsey model was fitted to the SBE EMC/equilibrium relative humidity (ERH) data and it was established that the residual oil content significantly affected the sorption isotherms. By considering an ERH of 67% or below to be a safe storage condition, the SBE should be stored at or below 12.2% moisture content (m.c.) if the temperature is at or below 20 °C and an the oil content is 7%. However, according to the respiration experiments it would be safe to store SBE up to 16% m.c. (equivalent to 75% ERH). Considering a DML limit of 0.1%, the allowable storage time of SBE at a m.c. lower than 15.4% (ERH of 75%) was at least 46 days. The widely accepted practice of incorporating the gums present in the extracted oil, diluted in water, back into the SBE should be avoided since it increases the m.c. of the product and substantially reduces the allowable storage time.     

MICROBIOLOGICAL QUALITY OF WHEAT STORED UNDER DIFFERENT CONDITIONS IN TURKEY

Four different types of wheat storage systems are widely used in the Marmara region. The existing storage conditions were studied and changes in the microbiological quality of the stored wheat under these conditions were assessed.
Depending on the external conditions, ambient temperatures and relative humidities in the stores were 17–26°C and 50–65% RH during summer and 3–10°C and 62–83% RH during winter, respectively. The low relative humidity level during harvesting and subsequent storage was adequate for obtaining low levels of moisture content and water activity in the produci for safe storage. The increase in relative humidity of the air during winter months did not affect the moisture content of the product considerably and the low temperature prevented mold growth. Therefore, all of the four different storage facilities were suitable for safe storage of grain for a period of one year without significant losses in quality due to microbiological load.     

Mycotoxin production in amber durum wheat stored at 15 and 19% moisture content

Ochratoxin A and citrinin developed in 11 kg parcels of amber durum wheat at 15% and 19% initial moisture content (MC) exposed to simulated bulk storage in a Manitoba granary for 60 weeks between July 1984 and September 1985. Other biotic and abiotic variables were monitored throughout the storage period. Ochratoxin A reached maximum levels of 11.8 and 0.11 ppm at 19 and 15% initial MC, respectively, during weeks 44-48; citrinin reached levels of 80.0 and 0.65 ppm at these respective moistures during the same period. The effect of 19% initial MC was significantly greater for the following variables: ochratoxin A, citrinin, Aspergillus flavus, Aspergillus glaucus group species, Alternaria species, Aspergillus versicolor, bacteria, fungal propagule count, seed germination, O2, CO2, moisture content, and fat acidity. Principal component analysis indicated that the first two components, describing greater than 60% of the variability in the data, partially defined the ecological relationships leading to mycotoxin production in the stored durum wheat system.     

Delineating the effect of gaseous ozone on disinfestation efficacy,protein quality,dehulling efficiency,cooking time and surface morphology of chickpea grains during storage

Ozone is one of the acceptable and economically viable techniques for treating grains during storage for its residue-free and environment-friendly nature. A laboratory-scale and pilot-scale ozone disinfestation system for chickpea grains was developed. Chickpeas conditioned to different moisture levels (10, 12, 14% wb), infested with Callosobruchus maculatus were stored at different temperatures (15, 23, 31 °C), with varying bed thickness (50, 75, 100 mm), and samples were disinfested by ozone gas at different concentrations (500, 750, 1000 ppm). Ozone concentration, moisture content of the grain, grain bed thickness, and storage temperature had significant (p < 0.01) effects on the disinfestation of C. maculatus insects. 100% insect mortality (adult and egg) and 79% germination were achieved when treated at 1000 ppm ozone for 5 consecutive days. The optimum treatment parameters were tested in pilot-scale bins (250 kg) and the germination ability, protein, milling, and cooking qualities of chickpea grain were evaluated after 6 months storage period. The protein content, germination ability, surface morphological analysis, milling, and cooking time were shown to profoundly deteriorate in the untreated samples as a contrast to that of the ozone-treated samples. Ozonation at higher doses resulted in the crack generation on the surface of the insect eggshell (5–38 μm) and chickpea pericarp (326–711 nm), with added advantages of improved dehulling efficiency of chickpea by 3.1% and reduction in the cooking time by 15 min. The SDS PAGE profiling exhibited major deviations in the protein bands in the stored chickpea. The essential amino acids (EAA) and total amino acids (TAA) decreased in the ozone-treated sample and control sample with storage; however, major deterioration was observed in the control sample stored for 6 months.     

The effectiveness of fenitrothion and malathion as grain protectants under bulk storage conditions in New South Wales, Australia

Fenitrothion at 2.5, 5.0 and 6.0 ppm was compared with malathion at 12.0 and 18.0 ppm for the protection of bulk wheat in vertical bin silos, and 10 ppm fenitrothion was compared to 18.0 ppm malathion in horizontal bulk depots. In both types of storage the persistence of the insecticides could be correlated with the temperature and moisture content of the grain. Under the conditions of silo storage, both protectants remained effective against Rhyzopertha dominica, Sitophilus granarius and secondary pests for as long as 19 months. Under the more severe conditions of horizontal bulk storage the higher applications were effective for only 6–7 months. Fenitrothion at one half the application rate of malathion appears to give equivalent protection against the deterioration of stored wheat caused by attack from stored product insect pests.     

小麦储藏水分、温度和真菌生长危害进程预测的研究

对小麦储藏水分、温度、真菌最初生长时间和危害进程进行了初步探索性研究。采用喷雾着水方法将样品水分调至13.2%、13.6%、14.0%、14.5%、15.1%、15.5%、16.9%,分别于10、15、20、25、30、35℃恒温箱模拟储藏,定期检测各样品真菌生长变化情况,周期为120 d。结果表明,小麦在不同温度储藏,随着温度增加,真菌生长速度加快,30℃时达到最高,35℃时生长速度降低。在6个试验温度中,从安全和经济角度评价,最佳储藏温度为20℃;16.9%水分的小麦,由于出现一些青霉生长,即使低温储藏,这个水分仍存在着较大风险;根据上述研究结果,研究首次提出了小麦储藏水分、温度和真菌最初生长关系曲线,小麦在不同温度下储藏,真菌危害进程所需的时间。由于储粮真菌生长影响因素的复杂性,本试验数据仅供参考。     

Lipid oxidation of brown rice stored at different temperatures

Changes in lipid oxidation and quality of brown rice stored at different temperatures were investigated. Fatty acid value (FAV), peroxide value (POV) and carbonyl value (CV) of brown rice were determined every 45 day for 270 day. Volatile compounds in seven samples stored for 0, 135 and 270 day were also identified. Relationships between volatile compounds and oxidative indices were analysed. Results revealed that the FAV, POV and CV of brown rice significantly increased (P < 0.05) with prolonged storage. Samples stored at low temperatures showed lower FAV, POV and CV than those stored at high temperatures. Brown rice stored under different conditions produced similar volatiles. Based on the principal component analysis of the volatiles, the first two principal components explained 58.20% of the variance. Volatiles of PC1 were correlated with FAV, POV and CV and can be used as an index to assess the quality of stored brown rice.     

A novel approach to authenticity control of whole grain durum wheat (Triticum durum Desf.) flour and pasta,based on analysis of alkylresorcinol composition

Since durum wheat is ∼20% more expensive than common wheat and considered of superior quality for the manufacture of pasta products, efficient methods for the detection of accidental or intentional admixtures of common wheat to durum wheat products are required. This paper describes a novel approach for the detection and quantification of whole grain common wheat adulteration in whole grain durum flour and dried pasta. We found that differences in the C17:0 to C21:0 alkylresorcinol homologue ratios between the two cereal species may serve as a suitable tool for whole grain durum product authentification. To detect and estimate adulteration, the C17:0/C21:0 ratios of flour and pasta admixtures with added whole grain flour of common wheat were analysed. A linear relationship between C17:0/C21:0 ratios and level of admixture in pasta samples showed that adulteration can be estimated within the range of 5–100% of admixture. Furthermore, di- and triunsaturated as well as oxygenated alk(en)ylresorcinols are reported to occur in Triticum durum Desf. for the first time.     

Application of common wheat bran for the industrial production of high‐fibre pasta

The study was conducted on the effect of the addition of common wheat bran on the chemical composition, physical properties, cooking quality and sensory traits of durum wheat pasta. The pasta was produced on an industrial scale, applying an addition of common wheat bran at doses ranging from 20 to 40%. The products obtained were compared to the pasta from whole‐grain durum wheat flour, produced under identical conditions and with commercially available whole‐grain durum wheat pasta. The increase in the content of wheat bran in the pasta caused a significant increase (Duncan test, P ≤ 0.05) of the content of protein, lipids, ash and total dietary fibre (TDF). The application of 25–30% addition of common wheat bran allowed obtaining the products which are as rich in dietary fibre as the pasta prepared at the same technological parameters from whole‐grain durum flour. The pasta containing up to 30% of bran was characterised with lower losses of dry mass and higher resistance to overcooking, in comparison with the pasta made of whole‐grain durum. Simultaneously, the products had very good sensory quality.