阿魏酸酯酶的制备及在肉鸡饲料中的应用

为了降低饲料中非淀粉多糖质量抗营养因子,提高肉鸡对饲料养分的利用,本文研究了固态发酵阿魏酸酯酶的工艺及其对饲料养分利用率的影响。结果表明：在麦麸与麦糟质量比为2∶8、蛋白胨与酵母粉质量比为2∶4、含水量为40%、接种量为10%、培养时间为6天、培养温度为33 ℃条件下,阿魏酸酯酶的酶活达到了29.49 U/g,较未优化前提高了5.11倍。将浓缩后的酶液与溢多酶AF831添加入肉鸡饲料中,发现添加溢多酶及阿魏酸酯酶可以提高干物质、粗蛋白、粗灰分、酸性洗涤纤维等利用率,但作用不明显,对中性洗涤纤维改善效果极显著（P<0.01）。     

Über die Aktivität der Phospholipase B der Gerste im Verlaufe der Entwicklung des Kornes

Activity of Phospholipase B in Barley During Growth of the Seed During growth of the barley seed the activity of phospholipase B, which cleaves both the fatty acid rests from lecithin, attains a maximum 13 days after flowering. After this period the activity decreases vey rapidly. The ripe seed exhibits a exhibits a small but distinct residual activity. The action of this enzyme in the formation of lysolecithin and the deposition of the latter in the starch particle is discussed.     

Über die Veränderung einiger Qualitätsmerkmale bei verschiedenen Ölleinsorten unter kontrollierten Klimabedingungen

Alteration of Several Quality Characteristics of Different Varieties of Linseed under Controlled Climatic Conditions In a phytotron experiment, 9 varieties of linseed from different countries were grown from flowering till ripening under 2 different day lengths (12^h and 19^h), 2 different temperatures (15°C and 23°C) as well as 2 different humidities (85% and 50%). Using these plant materials, the influence of climatic factors, such as photoperiod, temperature and humidity, on several important quality characteristics of linseed were studied with the aim to explain the differences observed in a world-wide field study¹. The crude fat content was generally increased at lower temperatures, however, several varieties behaved oppositely, yielding a higher oil content at higher temperatures. Also with regard to crude protein content, several interactions were found between the varieties and the climatic factors, so that no distinct negative correlation was obtained between crude fat content and crude protein content. These interactions, which were also observed in other quality criteria as well as in field experiments, hardly permit the exact prediction of the quality of linseed of various provenances if the variety is not known.     

Einfluß der Fettzufuhr und der Fettsäurezusammensetzung auf Mast- und Schlachtleistung sowie auf Parameter des Protein- und Lipidstoffwechsels beim Schwein

Influence of Fat Intake and Fatty Acid Composition on Fattening, Carcass Performance, and Protein and Lipid Metabolism of the Pig The influence of fat intake and fatty acid composition on the digestibility of the crude nutrients, deposition of protein and fat, in vitro fat synthesis from glucose and on several blood parameters has been studied in four experiments using 108 piglets and in a fattening study. In piglet experiment 1 (5%, 18% and 35% crude fat) and in piglet experiments 2 and 3 (2-7% soybean oil or lard) and 4 (12% sunflower oil or coconut oil) attempt was made to achieve, within each experiment, the same intake of digestible protein (DP) and metabolizable energy (ME). In fattening studies 2 and 3, the feed was given ad libitum. Replacement of carbohydrate energy by fat energy caused in all experiments a reduction in feed requirement, a lower insuline level, a lower fat synthesis from glucose and a higher fat deposition, whereas the type of dietary fat distinctly affected the fatty acid composition of the back fat.     

Pea–barley intercropping and short-term subsequent crop effects across European organic cropping conditions

Grain legumes are known to increase the soil mineral nitrogen (N) content, reduce the infection pressure of soil borne pathogens, and hence enhance subsequent cereals yields. Replicated field experiments were performed throughout W. Europe (Denmark, United Kingdom, France, Germany and Italy) to asses the effect of intercropping pea and barley on the N supply to subsequent wheat in organic cropping systems. Pea and barley were grown either as sole crops at the recommended plant density (P100 and B100, respectively) or in replacement (P50B50) or additive (P100B50) intercropping designs. In the replacement design the total relative plant density is kept constant, while the additive design uses the optimal sole crop density for pea supplementing with ‘extra’ barley plants. The pea and barley crops were followed by winter wheat with and without N application. Additional experiments in Denmark and the United Kingdom included subsequent spring wheat with grass-clover as catch crops. The experiment was repeated over the three cropping seasons of 2003, 2004 and 2005. Irrespective of sites and intercrop design pea–barley intercropping improved the plant resource utilization (water, light, nutrients) to grain N yield with 25–30% using the Land Equivalent ratio. In terms of absolute quantities, sole cropped pea accumulated more N in the grains as compared to the additive design followed by the replacement design and then sole cropped barley. The post harvest soil mineral N content was unaffected by the preceding crops. Under the following winter wheat, the lowest mineral N content was generally found in early spring. Variation in soil mineral N content under the winter wheat between sites and seasons indicated a greater influence of regional climatic conditions and long-term cropping history than annual preceding crop and residue quality. Just as with the soil mineral N, the subsequent crop response to preceding crop was negligible. Soil N balances showed general negative values in the 2-year period, indicating depletion of N independent of preceding crop and cropping strategy. It is recommended to develop more rotational approaches to determine subsequent crop effects in organic cropping systems, since preceding crop effects, especially when including legumes, can occur over several years of cropping.     

Effect of moisture,microwave heating,and live steam treatment on phospholipase D activity in soybeans and soy flakes

The impact of enzyme activity on the nonhydratable phospholipid content of crude soybean oil has been evaluated. A radiochemical method was used to assay phospholipase D activity in whole and flaked soybeans stored under a variety of storage and enzyme inactivating conditions. The crude enzyme was isolated and incubated with a mixture of¹⁴C-labeled and unlabeled phosphatidylcholine. The amount of liberated radioactive choline was used as a measure of enzyme activity. whole soybeans with moisture contents of 8–18% were stored at 40°C and sampled weekly for up to four weeks. Although the enzyme was active in all samples, the optimum moisture content for enzyme activity was about 14%. Flaking and flake thickness were shown to increase phospholipas D activity. At moisture levels above 10%, flakes at .012″ showed about twice the activity of whole beans. As flake thickness was increased, enzyme activity decreased. Whole soybeans with moisture contents of 12–18% were treated by microwave heating under controlled conditions. During the early stages of heating, the enzyme was activated, and then was gradually destroyed by the time the temperature of the beans reached 115–120°C. Approximately 8–10 min of microwave heating was required to completely destroy enzymatic activity. The inactivation of phospholipase D in soyflakes treated with live steam was also evaluated. The enzyme is rapidly destroyed at temperatures of about 110°C. Evaluations of flakes subjected to live steam and whole beans treated by microwave heating to inactivate phospholipase D suggest that heat, moisture and enzyme activity are important factors contributing to the formation of nonhydratable phospholipid in extracted crude oils. Presented at Annual Meeting of the American Oil Chemists' Society, May 3–7, 1989.     

Determination of deoxynivalenol (DON) in wheat, barley and corn and its relationship with the levels of total molds, Fusarium spp., colonization percentage and water activity

Fifty samples of cereals including 30 of wheat (10 of wheat hard red spring), 10 of wheat soft red winter and 10 of wheat durum ámber), 10 of barley and 10 of corn (5 of white corn and 5 of yellow corn) were analyzed to detect and determine by the TLC method, the quantity of deoxynivalenol levels, which is a toxic secondary metabolite produced by Fusarium species. The aw of samples and the internal and external micoflora and Fusarium spp. levels were also investigated. Results showed that the highest grade of infection (12-80%), and the highest count of total molds (3.9 Log UFC/g) were detected in wheat samples, while the highest levels of Fusarium spp. (2.3 Log UFC/g) were detected in white corn. Deoxynivalenol was found in the wheat and barley samples but not in corn. The wheat red winter soft samples showed the highest levels of deoxynivalenol (3.2 ug/g) which is over the limit levels accepted by the FDA. Correlation was not found among count of total molds, Fusarium spp., infestation grade, aw, and deoxynivalenol levels. These results suggest that it is necessary to exert measures to avoid and to control the importation of contaminated cereals with DON levels higher to those allowed.     

Some compositional properties of seeds and oils of eightAmaranthus species

Grain of 21Amaranthus accessions (eight species) was analyzed for crude fat, fatty acid profiles (FAP), and vitamin E (tocopherols and tocotrienols). Contents of (1→3), (1→4) β-glucan were determined in 12 accessions (four species), and trypsin inhibitor activity (TIA) in 20 accessions (six species). FAP and vitamin E profiles were compared to those of barley, buckwheat, corn, lupin, oat, and wheat oils. Crude fat content ranged from 5.2 to 7.7%, and of the oils examined, amaranth oil was most similar in FAP to corn and buckwheat oils. Amaranth was higher than all but wheat and lupin in tocopherol content but was virtually devoid of tocotrienols, which have been shown to have hypocholesterolemic activity. Amaranth grain did not contain (1→3), (1→4) β-glucans and was low in trypsin inhibitor activity (≤4.3 trypsin units inhibited/mg). Any hypocholesterolemic effects of dietary amaranth are apparently due to substances other than (1→3), (1→4) β-glucans or tocotrienols.     

Einlagerungen und Austausch von Linolsäure im Körperfett von Broilern bei zeitlich begrenzter Aufnahme verschiedener Öle und Fette

Deposition and Exchange of Linoleic Acid in Depot Fat of Broilers During the Uptake of Various Oils and Fats for Limited Periods The fat quality of slaughtered broiler bodies is mainly determined by two parameters, on the one hand by the viscosity, whose decrease leads to increased losses in body fat during the slaughtering process, on the other hand by the oxidation stability, whose deterioration makes the slaughtered body not eatable. Both parameters are determined by the share of polyen acids, above all of linoleic acid, in vegetable oils. As the fatty acid pattern of the body fat depends in a high degree on the feed fat and broiler rations contain 8–10% fat, the composition of the additional fat is of significant importance. A feed fat with high contents of long chained, saturated fatty acids causes, however, a smaller utilization for chicken in the first 3–5 weeks of life. Both demands, a sufficient viscosity or oxidation stability and a good utilization, lead to the reflection to feed first a high unsaturated vegetable oil and to change during the further fattening period to an animal fat. A corresponding test was carried out with 156 male broilers. Group 1 got throughout the feeding time sunflower oil, group 6 got lard, the other groups underwent a change in feed from sunflower oil to lard, each shifted for one week. During the weekly slaughters abdominal fat was removed for the investigation of fatty acid pattern and iodine value. Feed uptake, increase in weight and feed utilization showed no significant differences. The content of linoleic acid amounted on the 43th day of life in group 1 to 59%, in group 6 to 14%. In the groups with weekly changes the following data were found: group 2: 31.6% (22nd day of life), 19.3% (28th day of life), 17.8% (36th day of life), 16.6% (43rd day of life); group 3: 35.0% (28th day of life), 25.3% (36th day of life), 21.1% (43rd day of life); group 4: 39.4% (36th day of life), 28.7% (43rd day of life); group 5: 42.7% linoleic acid (43rd day of life). After the change to the ration with lard the share of linoleic acid in the abdominal fat diminished significantly. This decrease was the more lower, the later the change in feed took place. The low content of linoleic acid in group 6 was not achieved by any other test group. The determination of the iodine value led to corresponding results.     

Pearling barley and rye to produce phytosterol-rich fractions

Because of the positive health effects of phytosterols, phytosterol-enriched foods and foods containing elevated levels of natural phytosterols are being developed. Phytosterol contents in cereals are moderate, whereas their levels in the outer layers of the kernels are higher. The phytosterols in cereals are currently underutilized; thus, there is a need to create or identify processing fractions that are enriched in phytosterols. In this study, pearling of hulless barley and rye was investigated as a potential process to make fractions with higher levels of phytosterols. The grains were pearled with a laboratory-scale pearler to produce pearling fines and pearled grains. Lipids were extracted by accelerated solvent extraction, and nonpolar lipids were analyzed by normal-phase HPLC with ELSD and UV detection. Total sterol analyses were performed by GC. After a 90-s pearling, the amounts of pearling fines from hulless barley and rye were 14.6 and 20.1%, respectively, of the original kernel weights. During pearling, higher levels of phytosterols and other lipids were fractionated into the fines. The contents of free sterols and sterols esterified with FA in the fines were at least double those in the whole grains. Pearling fines of hulless barley and rye contained >2mg/g phytosterol compounds, which makes them a good source of phytosterols and thus valuable raw materials for health-promoting foods.     

prüfung von Leinfuttermitteln (Saat,Extraktionsschrot) an wachsenden Schweinen – Futterwert,Thiocyanat-und Schilddrüsenhormonstatus

Evaluation of linseed feedstuffs (ground linseed, solvent extracted linseed meal) with growing pigs – feed value, thiocyanate and thyroid hormone status. Ground linseed (Linum usitatissimum) was tested with 9 fattening pigs in a digestibility experiment. Barley (control diet) was partially replaced either by 25% or 50% ground linseed. In three periods three animals of each of the three groups (latin square) received a diet without or with 25% or 50% ground linseed. In two feeding experiments a total of 120 weaned piglets received diets either without and with 10% ground linseed or without and with 10% solvent extracted linseed meal (Exp. 2). A low apparent organic matter digestibility of 66% of ground linseed was primarily caused by 40% apparent digestibility of crude carbohydrates (crude fibre + N-free extract). In linseed groups the intake of lignin and its faecal excretion was high. It seems that the undigestible lignin is one, however not the sole reason of reduced digestibility. A relatively high metabolizable energy of 18MJ/kg linseed dry matter (DM) results from high fat content (40% of DM). Piglets receiving ground linseed tended to higher feed consumption as well as body weight gain and lower feed to gain ratio. As a tendency the consumption of diet with solvent extracted linseed meal and the daily weight gain were lower than in control (without linseed meal). Linseed feedstuffs drastically increased thiocyanate concentration of blood serum. Cyanide is released and detoxified via sulphur transferases to thiocyanate in organism.Thiocyanate impairs thyroid function, however, only in case of iodine deficiency. In case of 0.5 mg/kg diet supplementary iodine in piglet's experiments ground linseed had no effect on thyroxine and triiodothyronine concentration oi blood serum. A lower serum thyroxine concentration of piglets which were given the solvent extracted linseed meal resulted from other causes than from iodine administration (0.5 mg/kg diet).     

β-葡萄糖苷酶的发酵工艺优化及在木糖渣酶水解中的应用

木糖渣有较高的纤维素含量,可以用作诱导产生β-葡萄糖苷酶的碳源。本文以木糖渣为诱导碳源,优化了黑曲霉发酵产β-葡萄糖苷酶的工艺。首先利用Plackett-Burman实验设计在6个因素中筛选出了影响产酶的主要因素,分别为麦麸、硫酸铵、硝酸钠。在筛选基础上,利用三因素五水平的中心组合对3个因素进行了进一步的优化,并用响应优化器得到了产酶的最佳条件麦麸、硫酸铵、硝酸钠的浓度分别为26.7g/L、10.0g/L、10.0g/L,在得到的最佳条件下,酶活可以达到15.0IU/mL。对拟合模型进行了方差分析,结果表明模型的R²值为92.12%,P值为0,模型拟合较好,可以对实验结果进行预测。以木糖渣为底物,用诱导制备的复配酶液验证了其水解效率,结果表明当里氏木霉粗酶液与黑曲霉粗酶液1：1复配时,酶水解效率为里氏木霉粗酶液的4倍。     

Impact of the addition of an enzyme pool on an activated sludge system treating dairy wastewater under fat shock loads

BACKGROUND: The application of lipase‐rich enzyme pools (such as the crude solid enzymatic preparation (SEP) obtained from Penicillium restrictum solid‐state fermentation of agro‐industrial wastes) to activated sludge systems may be an effective strategy for preventing various operational problems. The continuous addition of SEP to the treatment system can become cost‐prohibitive when in situ production and/or storage are factored in. The application of SEP to high‐fat wastewater treatment would only be justified as an emergency measure, such as a sudden increase in the fat content of the bioreactor influent. Therefore, the primary objective of this work was to investigate the efficiency of a crude SEP during fat shock loads, simulated through the periodic addition of dairy industry waste containing high fat concentrations to the feed stock of an activated sludge system, operated in continuous mode. RESULTS: The test bioreactor exhibited a higher average chemical oxygen demand (COD) removal efficiency than the control bioreactor (83% for control and 90% for test) and the fat accumulation in the biological flocs of the test bioreactor was 3.2 times lower than that in the control bioreactor. Turbidity was also lower in the effluent of the test bioreactor (123 and 66 FTU in control and test, respectively) and it had a shorter recovery time between shock loads, especially when the interval between loads was shorter than one month (biweekly and weekly shock loads). CONCLUSION: The addition of SEP during fat overloads in the reactor feed maintained efficient COD removal in the test bioreactor for 270 days without any operational problems. Copyright © 2008 Society of Chemical Industry     

Über die Lipide der Gerstenstärke und ihre Veränderungen während des Wachstums der Gerste

Lipids of Barley Starch and Their Alteration During the Growth of Barley A brief account on the problems involved in the extraction of lipids from cereal starches is given. The composition of lipids in barley starch and its alteration during growth of the grain are reported. Lyso-lecithin constitutes the major portion of the lipids of barley starch. Since lyso-lecithin occurs as adduct with amylose, the content of amylose has been followed as well. The lipid content with respect to dry starch matter increases slightly during the growth. In contrast, the amount of lyso-lecithin in total lipids increases steadily till complete ripening; correspondingly, the amount of less polar lipids decreases to the same extent. The fatty acid composition of lyso-lecithins alter during the process of ripening.     

Variations of <Emphasis Type="Italic">trans</Emphasis> octadecenoic acid in milk fat induced by feeding different starch-based diets to cows

The impact of starch sources differing in their velocities of ruminal degradation on the milk fat of dairy cows was studied. The animals received diets containing a slowly degradable (potatoes) or rapidly degradable (wheat) starch concentrate (40% of the dry matter) in a total mixed diet. Milk fat was the only animal performance factor affected: Cows produced significantly less milk fat when fed the wheat diet than the potato diet (−3.3 g/kg, −122 g/d; P<0.05). With the wheat diet, milk fat was poorer in short-chain FA and richer in unsaturated longchain FA, especially in trans octadecenoic acid (4.4 vs. 2.7% of the total FA, P<0.05). A very large increase in the isomer trans-10 18∶1 (+1.46% of the total FA) was observed. Because no difference in volatile FA concentrations in the rumen was revealed, the increase in trans octadecenoic acids, and particularly the isomer trans-10 18∶1, was associated with the larger postprandial drop in ruminal pH with wheat. Similar concentrate levels and FA profiles in both diets indicated that the decrease in milk fat was due to changes in the ruminal environment. Quicker degradation of wheat starch, and hence a greater drop in pH with this diet associated with the absence of any effect on volatile FA, strengthen the hypothesis developed in the literature of enzyme inhibition via increased levels of trans octadecenoic acids, especially the trans-10 isomer. Hence, milk fat can be decreased with rapidly degradable starch sources and not only with high levels of concentrates in the diet or added fat. More detailed work is necessary to elucidate the microorganisms involved and to determine whether metabolic pathways similar to those reported for high-concentrate diets are involved.     

Fett in der Fütterung von Milchkühen - Wirkung eines verseiften Futterfettes auf Parameter der Milchleistung

Fat in Feeding of Milk Cows - Effect of a Saponified Feedfat on the Parameters of Milk Performance The effect of a saponified feedfat on the parameters of the milk performance during the first 100 lactation days was investigated on 43 cows, selected by accident. The cows got a daily basic ration of faded silage, offered ad libitum, 12 kg maize silage, and 1.5 kg molasses slices. Milk performance feed was rationed by a call plant, regulated by computer, beyond a milk performance of 12-14 kg for each cow and each day according to the formula 1 kg for 2 kg of additional milk. The milk performance feed of the control group (n = 22) contained 12 % of wheat, which was exchanged in the test group (n = 21) to 4 % of wheat bran and 8 % of saponified fat. The digestibility coefficients, obtained from wethers, showed for both milk performance feed energy contents of 7.9 (control) and 8.5 (test group) MJ NEL per kg TS. The amounts of milk, fat and protein were higher in the test group than in the control group. The difference in the milk amount were statistically significant till the 75th lactation day. Simultaneously the cows of the test group showed higher weights up to this point of time.     

Ernährungsphysiologische Wirkung erucasäurearmer Rapsöle auf Schweine 1. Entwicklung der Tiere und Schlachtbefunde

Nutritional Effect of Low-Erucic Rapeseed Oils on Pigs: 1. Development of Animals and Carcass Characteristics In a feeding experiment (17 weeks, 20 kg to 110 kg body weight) with 94 castrated males (Deutsche Landrasse) from a SPF colony the influence of type of fat, amount of fat, and concentration of erucic acid on growth, feed utilization, quality of slaughtered carcass, and development of some organs were studied. The feeds examined were a barley-soya ration with 2% residual fat without addition of fat, two soybean oil groups with 4% and 8% added fat, six mixed rapeseed oil groups with three different erucic acid concentrations (7.5%, 15%, 22.5%) at levels of 6% and 10% total fat in feed, as well as a Lesira oil group with 1.7% erucic acid at a level of 10% fat in feed. The daily increase on an average of all experimental groups was 0.76 kg and the feed utilization index (digestible energy) was similar in all experimental groups. Remarkable effects on the quality of slaughtered carcass were not detected. The relative mass of heart, kidney, spleen, and thyroids did not show any distinct alterations that were related to the dietary treatment. The liver was found to be distinctly heavier in the mixed rapeseed oil groups fed 10% fat in the feed; moreover, the effect of the amount of erucic acid was also observed. The adrenals of the mixed rapeseed oil groups were significantly lighter than those of the other groups; a relationship to the fat concentration or erucic acid concentration was not found.     

Programmed Cell Death in Developing Brachypodium distachyon Grain

The normal developmental sequence in a grass grain entails the death of several maternal and filial tissues in a genetically regulated process termed programmed cell death (PCD). The progression and molecular aspects of PCD in developing grains have been reported for domesticated species such as barley, rice, maize and wheat. Here, we report a detailed investigation of PCD in the developing grain of the wild model species Brachypodium distachyon. We detected PCD in developing Brachypodium grains using molecular and histological approaches. We also identified in Brachypodium the orthologs of protease genes known to contribute to grain PCD and surveyed their expression. We found that, similar to cereals, PCD in the Brachypodium nucellus occurs in a centrifugal pattern following anthesis. However, compared to cereals, the rate of post-mortem clearance in the Brachypodium nucellus is slower. However, compared to wheat and barley, mesocarp PCD in Brachypodium proceeds more rapidly in lateral cells. Remarkably, Brachypodium mesocarp PCD is not coordinated with endosperm development. Phylogenetic analysis suggests that barley and wheat possess more vacuolar processing enzymes that drive nucellar PCD compared to Brachypodium and rice. Our expression analysis highlighted putative grain-specific PCD proteases in Brachypodium. Combined with existing knowledge on grain PCD, our study suggests that the rate of nucellar PCD moderates grain size and that the pattern of mesocarp PCD influences grain shape.     

Untersuchungen zur Bewertung der Einsatzmöglichkeit verschiedener Futterfette in der Schweinemast

Investigations on the Use of Different Feeding Fats for Growing Fattening Pigs In a feeding experiment with 100 castrated male pigs (Deutsche Landrasse) two types of feeding oils (fat/fatty acid mixtures) were compared to four types of animal and vegetable fats (animal fat, soya oil, rapeseed oil and a licithine mixture). Their influence on growth, feed utilisation, quality of carcass and composition of body fat during a growing-fattening period from 20 kg-100 kg was investigated. The different types of fats were incorporated in a barley-soya-ration at a level of 4%. In addition one ration contained milled whole soya beans at a level equivalent to 4% fat. All groups were fed according to live weight the same amounts of digestible protein and metabolizable energy. During the whole growing-fattening period, the average daily gain of all groups was 0.78 kg, while the group given animal fat showed a small advantage over those given vegetable fat or feeding oils (fat/fatty acid mixtures). Feed convertion corresponded to these findings. But the differences of daily gain and feed convertion amounting to a maximum of 5% failed to reach significance. Remarkable differences of carcass quality were not detected. Fatty acid composition of backfat was strongly influenced by the type of fat in the ration. In the group fed a ration with animal fat the fatty acid composition of backfat was approximately the same as that of the control group. The groups of which the rations were supplemented with vegetable fats had an increased content of linoleic acid and linolenic acid and a decreased content of palmitic acid, stearic acid and oleic acid. Consequently, the iodine number of backfat in the groups supplemented with vegetable fats came up to 80. There was no difference observed in storage stability of backfat between the groups.     

Non-Uniformity of Surface Temperatures of Grain after Microwave Treatment in an Industrial Microwave Dryer

In this study, temperature rise and non-uniformity of heating of grain with different moisture contents after microwave treatment were investigated. The temperature anomalies after microwave treatment were measured for barley and wheat at four moisture levels (12, 15, 18, and 21% wet basis) and for canola at five moisture levels (8, 12, 15, 18, and 21% wet basis). Fifty grams of grain samples were heated in a laboratory scale, continuous-type, industrial microwave dryer (2450 MHz) at five power levels (100, 200, 300, 400, and 500 W) and two exposure times (28 and 56 s). Grain samples were thermally imaged using an infrared thermal camera as soon as they came out from the microwave chamber. Average, maximum, and minimum temperatures were extracted from each thermal image and the difference between maximum and minimum temperatures (ΔT) was calculated. The grain type had significant effect on the surface temperatures after microwave treatment. The surface temperatures increased with microwave powers and exposure times but decreased with moisture content. The average surface temperatures after microwave treatment were between 72.5 and 117.5°C, 65.9 and 97.5°C, and 73.4 and 108.8°C for barley, canola and wheat, respectively, when the applied microwave power was 500 W. At the same power level, the maximum surface temperature was between 100.3 and 140.0°C, 77.8 and 117.7°C, and 98.3 and 130.9°C for barley, canola, and wheat, respectively. Non-uniform heating patterns were observed for all three grain types at all moisture contents, power levels, and exposure times. The ΔT was in the range of 7.2 to 78.9°C, 3.4 to 59.2°C, and 9.7 to 72.8°C for barley, canola, and wheat, respectively. The location of hot and cold spots may vary in different dryers based on the position of magnetron and other components, but almost similar non-uniform heating pattern is expected in all microwave dryers. Therefore, this non-uniformity must be taken into consideration while developing microwave processing systems for grains.