Forced-air Oven Research Articles

Microwave-Oven Drying of Forage Samples Collected via Esophageal Fistula

Five laboratory trials were conducted to determine the effects of microwave-oven drying on the chemical composition of forage samples collected via esophageal fistula. Trials 1, 2, 4 and 5 were conducted as randomized complete blocks with two replications for trials 1, 2 and 4 and three replications for trail 5, with a split plot arrangement of treatments due to the use of duplicate samples. Trial 3 was conducted as a randomized complete block with four replications. Results from microwave-oven dried samples were compared with those from samples dried in a conventional oven (forced air) or freeze dried (FD). The effects of sample size, drying time and sample freezing, with respect to conventional oven drying, were also studied. Ash, N and hemicellulose were not affected (P>.05) by drying methods. However, concentrations of acid detergent fiber (ADF), acid detergent fiber N (ADFN), and neutral detergent fiber (NDF) tended to be higher in samples dried in either a microwave or conventional oven compared with FD samples. In vitro digestible organic matter (IVDOM) was consistently lower (P<05) in conventional-oven dried samples, compared with samples dried in a microwave over for 15 to 30 min. Microwave-oven dried samples (15 to 30 min) had higher (P<.05) IVDOM than FD samples when the forage was very mature, but FD samples tended to be higher in IVDOM than microwave-oven dried samples when forage was immature. Samples that were microwave-oven dried for longer than 30 min had higher (P<.05) IVDOM than FD samples, suggesting that a chemical change had occurred in samples exposed to microwaves for an extended period. Extended drying time, sample freezing before drying and sample size had no (P>.05) effect on chemical composition of samples dried in a conventional forced-air oven. Data suggest that forage samples collected via esophageal fistula could be microwave-oven dried for 15 to 30 min followed by drying in a forced air oven at 50 C without substantial change in forage chemical composition.

EFFECT OF KERNEL WATER CONCENTRATION AT HARVEST AND DRYING METHOD ON GRADES OF RED SPRING AND DURUM WHEATS

Effects of kernel water concentration at harvest, and windrow compared to artificial drying, were determined in two red spring (Triticum aestivum L.) and three durum (T. turgidum L. var. durum) cultivars. Grain harvested at kernel water concentrations of 1000 to &lt; 170 g water per kilogram kernel dry weight was dried in the field in simulated windrows or artificially in a forced-air oven (40–45 °C). Test weight and commercial grades were determined. Artificial drying of immature wheat reduced grades, primarily due to numbers of green kernels. Green kernel levels reduced grades of windrowed durum wheat in 1 of 3 years. In the absence of grade-limiting levels of green kernels, test weight limited grades of durum in 1 year, particularly in the windrowed treatment. In a separate experiment, percentages of green kernels were determined in field-scale windrowed and standing hard red spring and durum wheat crops. Levels of green kernels declined at similar rates in standing and windrowed crops. The kernel water concentration at which level of green kernels dropped to 0.75%, the maximum level tolerated in the top grades of hard red spring and durum wheat, was lower in dry years when maturity was forced than in moist years.Key words: Wheat (red spring), wheat (durum), windrowing, artificial drying, test weight

Automated Methods for Determination of Fat and Moisture in Meat and Poultry Products: Collaborative Study

A collaborative study was conducted to compare automated methods for rapid determination of fat and moisture in meat and poultry products with the official AOAC solvent extraction and forced-air oven methods, respectively. Fourteen products were tested, with fat and moisture contents ranging from 2 to 43% and 44 to 74%, respectively. Eight of the collaborating laboratories analyzed the products by using a moisture/fat analyzer; 4 laboratories used the AOAC methods. Standard deviations for within-laboratory repeatability, between-laboratory reproducibility, and bias for each product indicated that the rapid methods were acceptable. The moisture/fat analyzer methods have been adopted official first action for fat and moisture analyses in meat and poultry products.

Comparison of Top Round Steaks Cooked by Microwave-Convection, Forced-Air Convection and Conventional Ovens

AbstractThis study compared microwave-convection, forced-air convection and conventional electric ovens as to time and energy requirements, uniformity of cooking, and effect on cooking losses, sensory characteristics, moisture, fat, thiamin and riboflavin content of top round beef steaks. Sensory evaluation indicated no significant difference in juiciness; tenderness, including number of chews; intensity of beef flavor; and external color of the steaks cooked by the three ovens. Also, moisture, fat, thiamin and riboflavin content of the meat did not differ among treatments. Total cooking losses and percentage evaporation were greater (P<0.05) for steaks cooked in the microwave-convection oven than for those cooked by the other two methods. Drip losses were greater (P<0.05) with the microwave-convection than with the forced-air convection method of cooking top round beef steaks. The least total cooking time was required for the microwave-convection oven and the most for the forced-air convection oven. On a...

Use of the microwave oven for drying herbage samples in the field

Drying of herbage samples in the field using a microwave oven powered by a portable generator has saved time and eliminated the transporting of samples to other stations for handling. Microwave drying is compared to drying in conventional forced-air ovens and the influence of microwaves on chemical analysis of plant material is discussed.

Gas chromatographic determination of water and ethanol in silage by internal standard method

Water and ethanol contents of different silages were determined by solvent extraction gas chromatography. Methanol was used as internal standard. The gas chromatograph was equipped with thermal conductivity and hydrogen flame ionization detectors. Glass columns, length 1.5m, i.d. 2 mm, were packed with Chromosorb 101, 80/100 mesh size. Water and ethanol extractions of 10 silages and gas chromatographic runs of the extracts could be carried out daily. The methods are suitable for routine laboratory analysis and use of the internal standard allows the gas chromatographic runs to be performed faster and more accurately. The precisions of water and ethanol determinations were satisfactory, the mean relative standard deviation percents of 12 replicate analyses being respectively 0.22 and 2.55. Water content of silages was also determined by conventional forced-air oven drying at 105°C. When ethanol content of the silage was above 5 percent, there was a tendency for water contents obtained by the oven drying method to be over 5 percentage units greater than those obtained by solvent extraction gas chromatography. When the ethanol content was below 0.5 percent, high acetic acid and lactic acid contents with low pH resulted the same tendency, the difference between the methods varring from 0.5 to 2.2 percentage units.

Influence of Dairy Rations with Whole Cottonseed or Extruded Soybeans on Accuracy of Analyses for Milk Components

To determine whether dairy rations influence the accuracy of component analyses, fat, protein, lactose, and total solids were measured in milk produced by Holstein cows fed a basal ration or a ration containing either 7% extruded soybeans, 15% whole cottonseed, or 30% whole cottonseed for the first 15 wk postpartum. Samples from individual milkings were collected in the 14th and 15th wk from 12 or 13 cows in each group. Reference methods were Mojonnier for fat, Udy dye-binding for protein, polarimetry for lactose, and forced-air oven for total solids. The methods compared to reference methods were Milkotester and Babcock for fat and Infrared Milk Analyzer for fat, protein, lactose, and solids-not-fat. Fatty acid composition was determined by gas chromatography. For cows fed 30% whole cottonseed, Infrared Milk Analyzer fat measurements averaged .14% lower than by Mojonnier. For cows fed extruded soybeans or whole cottonseed, Milkotester fat measurements were higher than by Mojonnier, and Infrared Milk Analyzer protein measurements were higher than by Udy dye-binding. For cows fed whole cottonseed, Infrared Milk Analyzer solids-not-fat measurements were higher than by forced air oven. For cows fed extruded soybeans or whole cottonseed, differences between Babcock and Mojonnier fat measurements and between Infrared Milk Analyzer and polarimetric lactose measurements were not affected. For cows fed whole cottonseed, the mean molecular weight of the fatty aicds of milk fat was increased.

Microwave Drying of Rangeland Forage Samples

This study was conducted to compare the effectiveness of microwave drying with that of conventional forced-air oven drying of rangeland forage species. The data show that a microwave oven can dry grass forage samples for biomass production estimates without significantly affecting their nitrogen or phosphorus levels. Drying in a microwave for 10 minutes was comparable to drying in a forced air oven at 55’ C for 24 hours. In range surveys, mine reclamation permit programs, and other range forage evaluations, large numbers of relatively small clipped forage samples must be dried. Because of the locations of these surveys and programs, many of the workers do not have access to ovens of the size or number capable of drying these samples. Microwave radiation and other drying methods have been evaluated for stopping microbial and physiological processes and for their effects on the chemical components of plant materials (Darrah et al. 1977; Mayland 1968; Mayland et al. 1978). Mayland et al. (1978) evaluated the effect of freeze drying and oven drying at 40, 56, 70 or loo0 C on the extractable phosphorus (P) in alfalfa and sugarbeets. They concluded that the freeze drying, which caused no loss in dry matter, also caused less organic P hydroloysis than did oven drying. Wolf and Carson (1973) reported that microwave heating of alfalfa samples for 30 seconds, followed by forced-air drying was adequate to inactivate respiration. Microwave treatThe authors are soil scientists, U.S. Department of Agriculture, SEA-AR, High Plains Grasslands Research Station, 8408 Hildreth Rd., Cheyenne, Wyoming 82001 and Laramie, Wyoming, respectively. This article is a contribution from the SEA-AR, U.S. Dep. Agr. in cooperation with the Wyoming Agricultural Experiment Station, published as Paper No. JA 1055, Journal Series, Wyoming Agricultural Experiment Station. This research was supported in part by funds from the Environmental Protection Agency, Interagency Agreement: EPA-IAG-D5-E763. 426 ment resulted in similar nonstructural carbohydrates in the tissue when compared to freeze-dried material. Darrah et al. (1977) found that microwave drying caused heat damage to alfalfa and an orchardgrass-ladino clover mixture after only 12 minutes and 2 minutes of exposure, respectively. Also, levels of acid-detergent-insoluble nitrogen (N) were increased when the alfalfa and grass-clover mixture were exposed to microwave drying. However, drying plant material at 100” C in forced air ovens caused more heat damage than microwave drying. Some state regulatory agencies are requiring that forage samples bedried at 1100 C, which is undoubtedly resulting in heat damage and possible carbon loss. We conducted this study to compare the effectiveness of microwave and standard ovens for drying of rangeland forage species. Microwave drying could be very useful for personnel who are required to dry many herbage samples at remote locations to evaluate whether mine reclamation meets the state and federal requirements. Materials and Methods Samples of a native grass mixture [western wheatgrass (Agropyron smithii Rydb.), blue (Bouteloua gracilis (H.G.K.) Lag. ex Griffiths), buffalograss (Buchloe dactyloides (Nutt.) Englem.)] and of crested wheatgrass (Agropyron cristatum (L.) Gaertn.) were collected in mid-June and mid-August 1979 at the High Plains Grasslands Research Station, Cheyenne, Wyoming. Sample sizes were about the same as would be harvested from native range sites and crested wheatgrass seedings using a 1.92-ft2 (0.18-m2) frame. The sample weights for native and crested wheatgrass were 30 and 60 g, representing yields of 1,680 and 3,360 kg/ha, respectively. Samples clipped in June were placed in small paper bags and dried for 7.5 and 10 minutes in a Litton/Minute Master’ micro‘Use of trade name does not imply endorsement of this product by the USDA, but is used for the information of the reader only. JOURNAL OF RANGE MANAGEMENT 34(5), September 1961 Table 1. The comparison of microwave drying and forced air drying on forage moisture content, nitrogen and phosphorus of crested wheatgrass and a native grass mixture. Drying treatment Native grass mixture Estimated % Moist. % N %P Crested wheatgrass Estimated % Moist. % N %P Mid-June harvest* Microwave 7.5 minutes 36a*** 10 minutes 50b 7.5 + 5 minutes 43ab Forced Air Oven 55” C @ 24 hrs 48b Late-August harvest*** Microwave 7.5 minutes 42a 10 minutes 54b 12.5 minutes 54b Forced Air Oven 55” C @iI 24 hrs 53b 1.7a 1.6a .19a .22a 34a 51b 47b -

Cotton Moisture Measurements—Effects of Laboratory Procedures

ABSTRACT COTTON lint samples were dried in commercially available moisture testing ovens using a thermostat set-point of 105C. The moisture content determinations were satisfactory even though the temperatures at dif-ferent locations within the oven varied from 83 to 126C. A drying period of 1 h for lint'was found to be adequate in forced-air ovens and in ovens relying on natural con-vection air circulation. Drying cottonseeds for 3 h at 130C caused erroneous results because of scorching. Reliable cottonseed moisture data were obtained by dry-ing the seed for 12 to 16 h at 105C.

The Effect of Nitrogen, Phosphorus and Potassium Fertilization on Chemical Content of Sheep Diets

The Effect of Nitrogen, Phosphorus and Potassium Fertilization on Chemical Content of Sheep Diets

Total Solids in Nonfat Dry Milk by Atmospheric Drying in a Forced Air Oven

Abstract Laboratories using forced air atmospheric ovens at 100°C to determine total solids in milk are interested in using the same equipment to measure total solids in nonfat dry milk powder (NFDM). Results of several studies previously were presented to the Association. Another collaborative study involving 5 laboratories was done this year. The results of the new study confirm the previous work; the forced air method gives results not significantly different from the official vacuum oven procedure. Throughout these studies, it was noted that strong thermal gradients in some vacuum ovens made it difficult to uniformly subject each sample to the specified amount of heat. It was also found that fresh whole milk and reconstituted NFDM can be tested successfully when the steam bath step is omitted from the official method for milk by increasing the drying time to 4½ hr.

Residual porosity after impregnation of concrete with linseed oil/mineral spirits mixtures

Pore characteristics of concrete impregnated with boiled linseed oil were investigated using a mercury porosimeter. Prior to impregnations, specimens were dried either in a forced-air oven or with a gas-fired infrared heater. For impregnation, boiled linseed oil was mixed with various amounts of mineral spirits by weight. As the percentage of mineral spirits increased, the total specimen porosity increased, but the total porosity was still lower than that of the unimpregnated controls. Pore size distrubution shifted with impregnation and varied with the percentage of mineral spirits used. Regression analysis revealed relationships between the total intrusion, percent reduction in porosity, and total porosity versus percent boiled linseed oil by weight.

Power Absorption and Drying Patterns of Forage Crops Dried Will Microwave Power

ABSTRACTMicrowave power at 2.45 GHz is combined with unheated air in a multimode cavity to dry forage crops. Results show that rapid drying can be obtained in laboratory samples without high air temperatures and that some of the reduction in quality that occurs in oven drying can be avoided. Typical power consumption curves and drying patterns are presented. In vitro dry matter digestibility (IVDMD) and micro-Kjeldahl nitrogen analyses are used to establish a measure of the degree of improvement of this method of drying over that of the conventional forced-air oven.

Relative Frequency Distribution of D 125 C Values for Spore Isolates from the Mariner-Mars 1969 Spacecraft

Bacterial spore crops were prepared from 103 randomly selected aerobic mesophilic isolates collected during a spore assay of Mariner-Mars 1969 spacecraft conducted by the Jet Propulsion Laboratory. D 125 c values, which were determined by the fractional-replicate-unit-negative-most-probable number assay method using a forced air oven, ranged from less than 5 min to a maximum of 58 min. Subsequent identification of the 103 isolates indicated that there was no relationship between species and dry-heat resistance. A theoretical dry-heat survival curve of the “population” was nonlinear. The slope of this curve was determined almost exclusively by the more resistant organisms, although they represented only a small portion of the “population.”

Relative Frequency Distribution of D125 C Values for Spore Isolates from the Mariner-Mars 1969 Spacecraft

Bacterial spore crops were prepared from 103 randomly selected aerobic mesophilic isolates collected during a spore assay of Mariner-Mars 1969 spacecraft conducted by the Jet Propulsion Laboratory. D(125 c) values, which were determined by the fractional-replicate-unit-negative-most-probable number assay method using a forced air oven, ranged from less than 5 min to a maximum of 58 min. Subsequent identification of the 103 isolates indicated that there was no relationship between species and dry-heat resistance. A theoretical dry-heat survival curve of the "population" was nonlinear. The slope of this curve was determined almost exclusively by the more resistant organisms, although they represented only a small portion of the "population."

Effect of level and solubility of soybean protein on its utilization by young lambs.

Growth, digestibility and nitrogen retention trials were conducted to study the effect of dry heating soybean protein to reduce its solubility on nutrient utilization in sheep. The soybean meal was heated at 149° C. for 4 hr. in a forced-air oven, which reduced protein solubility from 72 to 35%. Growth rate was highest at the 14 % protein level and heating the soybean meal had an inconsistent effect. Feed efficiency was improved significantly (P<.05) by feeding the heated soybean meal. Rumen ammonia concentrations increased with protein level in both trials and showed a slight depression due to heating the soybean meal.

Amounts, Variations, and Interrelations of the Major Milk Components in Individual Farm Deliveries

Summary Raw milk from 607 farms was analyzed during summer and again during winter for per cent milk fat (fat), total solids (TS), and total protein (TP). Fat was by Babcock; TS in a forced-air oven; and TP by alkaline steam distillation. Per cent solids-not-fat (SNF) and lactose-mineral (LM) were by difference. The averages and standard deviations for fat, SNF, TP, and LM, respectively, were: 3.89±0.45, 8.67±0.31, 3.29±0.23, and 5.38±0.22. The TS, fat, TP, and SNF averaged, respectively, 0.29, 0.22, 0.15, and 0.07% higher in winter, but the LM averaged 0.08% lower. The correlations were: between TS and fat, 0.93; SNF and fat, 0.60; LM and fat, 0.10; TP and fat, 0.74; and TP and SNF, 0.71. The interrelations of these components also were shown by regression coefficients and estimating equations.

A Comparison of Nitrogen and Energy Determinations on Fresh and Oven-Air Dried Cattle Feces

Summary Samples of fresh cow feces, obtained from 12 different animals, were subjected to analysis for total moisture (dry matter), nitrogen, and gross energy. These analyses were made both on the fresh and on the oven–air dried materials. Total moisture of the fresh feces was determined in three ways, and gross energy of the fresh feces was determined with the aid of two different primers, 95% ethyl alcohol and benzoic acid. Gross energy of the dried feces was determined without the use of any primer. The samples of fresh feces were dried in a forced-air oven for a period of 22 hr. at a temperature of 65° C. Small but consistent losses of nitrogen, average of 5.15%, occurred upon drying, as well as the liberation of 727mg. of carbon dioxide per 100g. of fresh feces. The average levels of the determinations of gross energy were 66.31, 71.17, and 71.24 Calories per 100g. of fresh feces for the ethyl alcohol, benzoic acid, and oven–air dry methods, respectively. The composite standard errors between duplicates for the energy determinations, expressed as Calories per 100g. of fresh feces, were 3.70, 2.17, and 0.22 for the ethyl alcohol, benzoic acid, and oven–air dry methods, respectively. Under the conditions of drying fresh cow feces employed in this experiment, only small losses of nitrogen occurred, and there was no loss of gross energy.