Wheat Moisture Research Articles

Biochemical characteristics of wheat and their relation with apparent metabolisable energy value in broilers with or without non‐starch polysaccharide enzyme

AbstractExogenous non‐starch polysaccharide (NSP) enzymes do not always exhibit the same improvement in AMEn (apparent metabolisable energy corrected for nitrogen balance) in wheat‐fed broiler chickens. In order to understand the factors that determine this variation, the in vitro mode of action of an NSP enzyme preparation (Rovabio™ Excel) was investigated in several wheats and wheat extracts. In vivo experiments were also performed in broilers fed seven different wheat cultivars. In vitro studies showed an important solubilisation of insoluble arabinoxylan (AX) in wheat flours, ranging from 65 to 85% depending on the wheat cultivar. The negative correlation observed between arabinose/xylose ratio and AX solubilisation (r2 = 0.45, P = 0.001) suggests that the variation in solubilisation can be partly explained by the AX structure. NSP enzymes are also able to hydrolyse wheat bran AX by 30–50% depending on the enzyme dosage. Whereas rapid solubilisation of insoluble AX was confirmed in pig digestive physiological conditions (TIM‐1), only a minor proportion of AX was hydrolysed as <8 kDa oligomers and then absorbed. In vivo studies on wheat‐based diets showed an average AMEn improvement of 108 kcal kg−1 dry matter (DM) (P < 0.001), but a large variation in enzyme efficacy (up to 200 kcal kg−1 DM) was observed. Among the wheat characteristics measured, only a significant negative correlation between AMEn improvement and wheat moisture content was found (r2 = 0.71, P = 0.035). A tendency of positive correlation between AMEn improvement with Rovabio™ Excel and the arabinose/xylose ratio of water‐soluble AXs of wheat (r2 = 0.42, P = 0.068) and between the arabinose/xylose ratio of water‐soluble AXs and the moisture content of wheat (r2 = 0.52, P = 0.064) was also observed. It can be deduced from the results that the AX structure might influence the efficiency of enzyme supplementation. In feed, Rovabio™ Excel quickly solubilises the different AXs of various wheat cultivars as a result of its broad enzyme activity profile. However, relationships between wheat characteristics and the response of wheat batches to enzyme addition are not yet fully understood. Copyright © 2006 Society of Chemical Industry

Thermal Kinetic Parameters of Thiamin in Wheat Flour at Temperatures Higher than 100°C

Kinetic parameters for thiamin degradation were obtained using 2 high-temperature heating methods: (1) atmospheric pressure (AP) with moisture correction and (2) controlled pressure (CP). At AP conditions, 33.3% dry basis(db) moisture wheat flour with 0.35% (db) thiamin was heated in thin steel cells isothermally at 145, 160, and 172 °C. To obtain the moisture correction factor, a constant-moisture study was conducted at 80 °C using 6 moisture contents (6.1% to 36.9%). At CP conditions, flour at 19%, 28.2%, and 33.3% (db) moisture in double-seamed cans was heated in a CP steam retort at 129 °C. For the AP method, the corrected activation energy for 33.3% moisture content was 129.5 kJ/g-mol and reaction rate at 80 °C was 3.48×10 - 4 min - 1 . Using the CP method, the activation energy and reaction rate were 121.0 kJ/g-mol and 9.69×10 - 5 min - 1 , respectively. Results obtained from 2 methods were not statistically different. These results illustrated that the correction method could be used as an alternative for researchers without access to controlled pressure equipment and transient heat transfer software.

Acoustic on-line grain moisture meter

A prototype of an acoustic on-line grain moisture meter was designed and developed. It consists of a funnel to produce a continuous grain stream with about 72 cm 3 s −1 flow rate falling onto a 30° inclined sensor surface with 150 mm diameter. A microphone, which is placed underneath the surface, receives sound waves generated by kernel impact and converts them to an electronic signal. The sensor was insulated to eliminate the ambient noise effects. Through the experiments the sound pressure level (SPL) variations of the impact sound were measured as output voltage and their relationship with grain moisture content was determined. In the first experiment, effects of grain drop height and types of impact surfaces (glass, wood and metal) on SPL were evaluated. Results showed that a drop height of 10 cm with the glass sensor surface had the best calibration equation ( R 2 = 0.94) with the highest accuracy and sensitivity for wheat moisture measurement. In the second experiment, effects of wheat varieties (Mahooty, Karaj-3 and C-73-18) with the selected impact surface (glass) and grain drop height (10 cm) on the output voltage related to SPL, were studied. Relationships between the output voltage and kernel moisture content for three wheat varieties were developed as calibration equations. The maximum instrumental error in 8–20% moisture content range was 1.25%.

Characterization of wheat-based biscuit cooking process by statistical process control techniques

A commercial wheat-based biscuit cooking process was characterized using statistical process control (SPC) techniques. These techniques included histograms, analysis of means (ANOM), control charts, process capability studies and Gauge Repeatability and Reproducibility (Gauge R&R). The production variables studied included raw material variables (wheat protein and moisture content) and product variables (biscuit breaking strength, moisture content and thickness of biscuit). The plant studied has three independent production lines, so product variables were analysed separately for each line. ANOM indicated that several process means were significantly different ( α=0.05) from the grand mean (breaking strength line 3, product moisture content line 3 and thickness of biscuit in all lines). Control charts indicated that some observed variables were not in statistical control (wheat protein and moisture content, breaking strength line 3 and thickness of biscuit for lines 1–2). Results from capability studies showed that all observed variables except wheat moisture content were not capable. Notably, there was a large variation in the thickness of biscuit. Gauge R&R suggested that the measurement system used was inadequate, contributing to the variation found in the process characterization. Initial investigation of the relationship between raw material variables and product variables in each line found no correlation.

Characterization of wheat-based biscuit cooking process by statistical process control techniques

A commercial wheat-based biscuit cooking process was characterized using statistical process control (SPC) techniques. These techniques included histograms, analysis of means (ANOM), control charts, process capability studies and Gauge Repeatability and Reproducibility (Gauge R&R). The production variables studied included raw material variables (wheat protein and moisture content) and product variables (biscuit breaking strength, moisture content and thickness of biscuit). The plant studied has three independent production lines, so product variables were analysed separately for each line. ANOM indicated that several process means were significantly different (α=0.05) from the grand mean (breaking strength line 3, product moisture content line 3 and thickness of biscuit in all lines). Control charts indicated that some observed variables were not in statistical control (wheat protein and moisture content, breaking strength line 3 and thickness of biscuit for lines 1–2). Results from capability studies showed that all observed variables except wheat moisture content were not capable. Notably, there was a large variation in the thickness of biscuit. Gauge R&R suggested that the measurement system used was inadequate, contributing to the variation found in the process characterization. Initial investigation of the relationship between raw material variables and product variables in each line found no correlation.

Design and scaling of wheat dough extrusion by numerical simulation of flow and heat transfer

This paper proposes a computational method to obtain simultaneous scale-up of mixing and heat transfer in single screw extruders by several parametric 3D non-isothermal numerical simulations. The numerical experiments of flow and heat transfer modeling studies are conducted using the Mackey and Ofoli [Cereal Chem. 67 (1990) 221] viscosity model for low to intermediate moisture wheat doughs in the metering section of a single screw extruder. The non-isothermal flow model includes viscous dissipation and the complete three-dimensional flow geometry including leakage flows without any simplifications such as unwinding the screw. Based on Rauwendaal [Polymer Extrusion, Hanser Publishers, New York, 1986] residence time distribution (RTD) and specific mechanical energy (SME) were chosen as the design parameters for the scale-up of mixing and heat transfer respectively. Parametric numerical simulations were conducted by varying screw geometric variables such as helix angle, channel depth, screw diameter to channel depth ratio, screw length to screw diameter ratio, and the clearance between the screw flights and barrel. SME and RTD curves vs. screw parameters were developed from the numerical simulations. From the design charts two differently sized extruders were obtained which had a scale-up of about 10 times based on throughput rates but had the same RTD and SME.

Three-dimensional distribution and sampling indices of insects and mites in horizontally-stored wheat

Studies were conducted in three flat storerooms in Southern Greece, filled with approx. 45 tons of wheat each, stored in 1.5 m deep bulks, in order to examine the seasonal abundance of insect and mite species, in relation to their horizontal and vertical spatial distribution into the bulked grain. For this purpose, wheat samples were taken from June 2000 until March 2001, at 10-day intervals, by using a partitioned grain trier. The surface of the grain bulk was divided into three sampling zones, the central zone (the central part of the bulk), the edge zone (close to the walls) and the corners (the corners of the store rooms). The trier samples were examined separately for the upper, medial and lower 0.5 m of the bulk. Significant differences were recorded for wheat moisture content among zones (p<0.0001) and among depths (p=0.0012). On the contrary, no significant differences were noted for temperature among zones (p=0.2281) and depths (p=0.3049). In general, the moisture content was higher in the upper 0.5 m of the bulk, compared to the other two depths. Temperature decreased during the sampling period and this reduction was more vigorous from October and on. Eight insect species and 25 mite taxa were found during the sampling period. The most abundant insect species were Plodia interpunctella Hubner (Lepidoptera: Pyralidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) and Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae). The most abundant mite species were Acaropsis sollers Rohdendorf (Prostigmata: Cheyletidae), Tyrophagus putrescentiae (Schrank) (Astigmata: Acaridae) and Glycyphagus domesticus (De Geer) (Astigmata: Glycyphagidae). For the majority of the most abundant insect and mite species, the highest population densities were recorded during autumn. More individuals were found at the corners and the central zone, compared to the edge zone. In addition, significantly more individuals were found in the upper 0.5 m of the bulk (p<0.05), compared to the other two depths, with the exception of A. sollers which was equally distributed in the upper 1 m. All the aforementioned species of insects and mites showed an aggregated spatial pattern, as indicated by Taylor's Power Law estimates. The use of Taylor's parameters for the estimation of accuracies and sample sizes for the most abundant species indicated that these parameters were notably varied among species.

Effect of l‐Cysteine on the Rheological Properties of Wheat Flour

ABSTRACTExtrudate expansion of cereal‐based products is largely dependent on the molecular interactions and structural transformations that proteins undergo during extrusion processing. Such changes strongly influence the characteristic rheological properties of the melt. It is possible to modify rheological properties of wheat flour during extrusion processing, in particular shear viscosity, with cysteine. The objective of this work was to further develop an understanding of the molecular interactions and structural transformations of wheat flour from dynamic oscillatory rheological measurements. Temperature and frequency sweeps were conducted in the linear viscoelastic range of the material. Changes in the storage modulus (G′), the loss modulus (G″) and the loss tangent (tan δ) of 25% moisture wheat flour disks as a function of cysteine concentration (0–0.75%) were monitored. Molecular weight between cross‐links (Mc) and the number of cross‐links (Nc) per glutenin molecule were determined from frequency sweep data. Increasing cysteine concentration broke cross‐links by decreasing G′ maximum and increasing tan δ values. Molecular weight between cross‐links increased and the number of cross‐links decreased. G′ values from temperature sweeps showed a similar trend. This information leads to a better understanding of the viscoelastic behavior of wheat flour doughs during extrusion cooking and elucidation of protein‐protein reaction mechanisms and other interactions in extruded cereal‐based snack foods.

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°C to 37 d at 10°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°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°C, respectively. Respiration rates and germination percentages of 15 and 16% m.c. wheat stored at 25°C remained constant for 70 d. The respiration rates of 17–19% m.c. wheat at 25°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°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.

Developing Agreement Between Very Short Flow and Longer Flow Test Wheat Mills

ABSTRACTVariations in soft wheat moisture content and kernel texture greatly affected the flour yield produced by a small (short flow) microtest mill (Quadrumat Jr.). An algorithm was developed that adjusted Quadrumat Jr. flour yield to 15% wheat moisture content, precluding the need to temper the wheat before milling. Another algorithm was developed to adjust Quadrumat flour yield relative to a constant softness equivalent (measurement of kernel texture) obtained during the micromilling procedure. Predicting the flour yield of the longer flow Allis‐Chalmers mill from Quadrumat Jr. unadjusted flour yield (R 2 = 0.55) was compared with predicting Allis‐Chalmers flour yield from the Quadrumat Jr. adjusted flour yield (R 2 = 0.90) across five diverse confirmation data sets. An algorithm to adjust flour yield for softness equivalent was individually developed for soft and hard wheats. Representative micromilling flour yield and softness equivalent data could be produced using as little as 10 g of untempered wheat and ≈3 min of operator time.

Regression Analysis of Microwave Spectra for Temperature-Compensated and Density-Independent Determination of Wheat Moisture Content

Partial least-squares regression (PLSR) was used to generate wheat moisture content predictive models from eight-frequency microwave attenuation (A) and phase (P) spectra in the 10.36 to 18.0 GHz range, as obtained by a free-space technique with a 10.4 cm thick sample. Spectra (n = 379) were measured for a set of grain samples that had been treated to span the agriculturally practical ranges of moisture content (M) (10.6 to 19.2% g/g wet), temperature (K) (- 1 to 42 C), and bulk density (D) (0.72 to 0.88 g/mL). The sample property space formed by M, K, and D was used to prune redundant samples and select representative subsets for calibration (n = 279), cross-validation (n = 40 segments), and testing (n = 31). Twelve model types are reported and vary from attenuation or phase alone to the combination of attenuation, phase, temperature, and density (i.e., APKD). For optimization of each PLSR model, the raw spectral, temperature, and density data were preprocessed with variable ratios, mathematical transformations, and/or variable scaling. The lowest moisture prediction errors were for temperature and density-corrected models with variables AKD or APKD; these produced root-mean-square cross-validation and prediction errors (RMSECV and RMSEP) of 0.19 to 0.20% in moisture content units. The more practical unifrequency models, APK at 15.2 GHz, and AK at 18.0 GHz, yielded RMSECV values of 0.21% and 0.35%, respectively. Addition of temperature to dielectric data always substantially reduced the model error. However, the multiplicative effect of density is well corrected by using the ratio A/P, or partly corrected by using the features in the attenuation spectra. Data trends suggest that dual-frequency PK models might benefit from a wider frequency range, and unifrequency AK models might be better at frequencies higher than 18.0 GHz. The results presented make it possible to evaluate a wide variety of instrumental configurations that might be proposed to suit particular engineering criteria such as measurement accuracy, range of operating conditions, and hardware complexity.

Comparison of Density-independent Expressions for Moisture Content Determination in Wheat at Microwave Frequencies

The accuracy of moisture content determination in grain from measurement of electromagnetic parameters is known to be dependent on the bulk density of the sample used for the measurement. Various means of limiting this effect have been considered in the past. This paper identifies various density-independent expressions developed for this purpose and compares their effectiveness in minimizing the density dependence of the predicted moisture content. The same procedure and data set from more than 180 measurements on hard red winter wheat,Triticum aestivumL., at frequencies of 11·3 and 16·8 GHz on samples in free space were used for the comparison. Several density-independent expressions were identified that predict wheat moisture content with a standard error of calibration of about 0·2% moisture for moisture contents ranging from 10·6 to 18·2% w.b. Although these results were obtained for static samples of grain, the principles can be extended to grain flowing through a tubular conduit, or moving on a conveyor, for continuous measurements.

Effect of Wheat Moisture Content on Meal Apparent Particle Size and Hardness Scores Determined by Near‐Infrared Reflectance Spectroscopy

ABSTRACTThe AACC Approved Method for near‐infrared reflectance (NIR) spectroscopy to produce a wheat hardness score for wheat market classification can be corrected for variation in wheat moisture content. The cause of the variation in NIR spectra resulting from variation in wheat moisture was investigated. Ten samples each of soft red winter, soft white winter, hard red winter, and hard red spring wheats were stored at 20, 40, 60, and 80 equilibrium relative humidity. Wheats were then ground on a cyclone grinder as required by the standard method. Variation in unground wheat kernel moisture content resulted in variation in NIR data. NIR log 1/reflectance values increased at all wavelengths as wheat moisture content increased. Spectral changes were related to changes in the apparent particle size of ground wheat meal as it was influenced by moisture content. Higher moisture contents produced slightly higher apparent particle size in meal, suggesting larger particles of pericarp that became more pliable at higher moisture (temper) levels. The apparent particle size of meal of high moisture wheats resulted in greater NIR radiation scattering and decreased reflectance. Meal moisture content itself had no effect on the two NIR wavelengths used to evaluate wheat hardness.

Comparative effects of subterranean clover, medic, lucerne, and chickpea in wheat rotations, on nitrogen, organic carbon, and moisture in two contrasting soils

The effects of subterranean clover, medic, and lucerne, grown simultaneously from 1988 to 1990, followed by wheat from 1991 to 1993, and of chickpea and long fallow in alternate years with wheat, on soil total nitrogen (N), nitrate-N (NO-3-N), organic carbon (C), and moisture were measured over 6 years in 2 long-term experiments on a black earth (pellic vertisol) and red clay (chromic vertisol) in northern New South Wales. The accretion of soil total N in the black earth and NO-3-N in both soils was higher after lucerne than after other legumes, and NO-3 in the black earth remained high after lucerne to the full depth (120 cm) of measurement during the following 3 years of wheat growing. Clover had the next largest effect on total N and NO-3 accretion, and chickpea had the smallest effect except in the red clay where chickpea increased NO-3 more than medic in 1990. However, none of the annual legumes had much effect on NO-3 after the first year of cropping and their small residual effects, if any, were confined to the top 30 cm of soil. Levels of total N accretion after lucerne were higher than previously measured, because of the greater depth of measurement, but were similar on a per unit depth basis. High levels of NO-3 -N after long fallow, especially in the black earth, which tended to be higher than after medic or chickpea, were probably caused by accelerated mineralisation of organic N which has declined more in this rotation than in any other. There was no accumulation of organic C during the legume growing period in any rotation, and C tended to be lower after chickpea than after other legumes. Organic C was almost always lowest in the long fallow treatment. Summer-growing grasses, which occurred in all treatments to varying degrees, may have caused the organic C accumulation during the 3 years of cropping. In the first year of wheat growing, soil water was lower after lucerne than after other treatments and highest after long fallow, continuous wheat, and chickpea. It was replenished in the red clay to field capacity in all treatments by high rainfall during the fallow before the first wheat crop but not in the black earth, which failed to reach field capacity in any treatment even 2.5 years after the pasture legume phase.

Analysis of Density-independent Equations for Determination of Moisture Content of Wheat in the Radiofrequency Range

The accuracy of determination of the moisture content of grain and seeds by estimation of their dielectric properties is well known to be dependent on the density of the samples. Where measurement involves the use of bulk samples of whole grain, as in a parallel plate or concentric cylinder capacitor, if the temperature is held constant, it is the bulk densitywhich primarily influences the measured value of material of a given moisture content. A range of mechanical and electrical means of minimising this effect has been put forward by previous authors. The present paper reviews the electrically based solutions; these have been investigated and an analysis made of their effectiveness in minimising the density dependence of the measured dielectric values for static samples. A range of excitation frequencies from 500 kHz to 5 MHz was employed in laboratory experiments on hard winter wheat, Triticum aestivumL., varieties Mercia, Hereward, and Hussar, which were preconditioned to moisture contents from 10 to 22% wet basis. The bulk density of the samples was controlled between 665 and 873 kg /m 3in a concentric cylinder capacitor. Of the models investigated for the correlation of the dielectric parameters of static samples of grain and moisture content, the most satisfactory in terms of the size of the errors involved, was the single frequency method based on the density-independence of the function [( ϵ′-1)/ϵ″].Non-linear regression analysis using data from varieties Mercia and Hereward yielded an equation capable of estimating wheat moisture content with a standard error of calibration of about 0·3 percentage point for moistures ranging from 11 to 22% at 1 MHz. The two-frequency, two-parameter method involving the measurement of the permittivity and the natural logarithm of the loss factor, also provided a result which is well within the performance expected of commercial moisture meters.

Milk Yield and Composition of Dairy Cows Fed Concentrate Based on High Moisture Wheat or High Moisture Corn

Thirty-six Ayrshire cows were assigned to 18 pairs and were blocked within parity (5 pairs of primiparous heifers and 13 pairs of multiparous cows); pairs had similar calving dates. The study, which was conducted over 3 yr, was designed to determine the effects of high moisture grain on milk yield and composition and to determine in vitro DM digestibility and ruminal degradabilities of DM, N, and starch of high moisture grains. Treatment diets consisted of isonitrogenous and isoenergetic concentrates that were based on high moisture wheat or high moisture corn. Both groups were fed a mixture of grass silage, grass hay, protein supplement, and a vitamin and mineral mix for ad libitum intake. Treatment diets were fed from wk 4 to 29 and from wk 4 to 37 of lactation for cows in first and second lactations, respectively. There was no interaction between treatment diet and year of lactation. Cows fed high moisture wheat had higher 4% FCM than did cows fed high moisture corn. Milk composition was similar for the two treatment diets. Ruminal degradabilities of DM and starch were higher for high moisture wheat than for high moisture corn. In vitro DM digestibility was higher for high moisture wheat (90.5%) than for high moisture corn (71.6%). This greater digestibility contributed to the higher milk yield of dairy cows fed high moisture wheat.

Comparison of Mathematical Models to Simulate Aeration of Wheat Stored in Brazil

Equilibrium and non-equilibrium heat and mass balance models are compared to simulate aeration of stored wheat under tropical and subtropical climates using both linear and non-linear airflow distributions. The approach used was to compare deviations in predicted grain deterioration instead of deviations in grain moisture content and temperature. The results produced by the equilibrium and non-equilibrium models were significantly different ( P=0·05)when simulating aeration of wheat stored for 1 yr in Curitiba, Brazil because the deviations in grain deterioration were equal to or greater than the uncertainty in predicting deterioration (±30%) for most test conditions. The non-equilibrium model appears more appropriate than the equilibrium model for simulating aeration of stored wheat because it is based on experimental thin-layer drying and wetting equations and equilibrium moisture content equations for desorption and adsorption. In addition, the equilibrium model over-predicts wheat moisture content and temperature, causing an over-prediction of grain deterioration. It is concluded that a more accurate deterioration model is needed to increase the uncertainty in predicting wheat deterioration for simulated aeration of stored wheat.

Sorption of methallyl chloride on wheat

A gas chromatographic technique is described for determination of β-methallyl chloride applied to small samples of wheat. Sorption after 24 hr exposure was high, varying from 63.7 to 70.2% of the initial dosage, but was significantly reduced by lower wheat moisture content. Methallyl chloride has potential as an alternative fumigant for disinfesting small grain sacks and seed stocks for livestock.

A technique for separation of wheat germ by impacting and subsequent grinding

A technique was developed for the separation of the embryo and scutellum, which make up the wheat kernel germ, with improved yield and purity. The wheat embryo was separated prior to grinding by using the impact action of a horizontal scourer. Factors influencing embryo separation and the optimum working parameters of equipment for processing four classes of wheats were studied. A wheat moisture content of 13-5 % (w/w) and a working volume of 5-95 7[ ma/kg for the impacting scourer were the parameters that gave optimal embryo extraction and minimized kernel breakage. The yield of pure and intact wheat embryo ranged from 0-74 to 120 % on a wheat weight basis, which represented 53-6 to 91-6 % of wheat embryos present in samples dissected by hand. Subsequently, in the milling process the scutellum was separated by proper sieve selection of the 2 BK and 3 BKf and a grinding gap of 0279 mm for 3 BKf roll. The scutellum was purified using a gravity table, with a yield ranging from 0-75 to 1-75 % on a wheat weight basis. The embryo and scutellum products had high protein and crude fat contents. Removal of the embryonic axis, scutellum, and some additional flaked embryo during the process did not affect wheat milling quality. The flour's chemical composition was also unaffected, but the protein and fat contents of the mill feed were reduced. The germ products resulting from the new technique retain both morphological integrity and chemical composition.

Amorphous silica as an additive to dust formulations of insecticides for stored grain pest control

Sitophilus oryzae, Tribolium confusum, and a susceptible and a malathion-resistant strain of Tribolium castaneum were bioassayed in wheat admixture against an amorphous silica, 2% pirimiphos methyl dust, 4% malathion dust, 9:1 w/w mixtures of the amorphous silica with the two insecticidal dusts, and 0.1 and 0.2% formulations of pirimiphos methyl and malathion respectively adsorbed on the amorphous silica. Bioassays were conducted at 15 and 25°C and at wheat moisture contents of 9.0, 14.5 and 16.5%. The silica alone and in combinations with the insecticidal dusts gave limited mortality of S. oryzae at concentrations which could be evenly mixed with the grain when bioassayed at 15°C and 14.5 or 16.5% wheat m.c. No cross-resistance to silica was observed in the malathion-resistant strain of T. castaneum. The toxicity of formulations of the insecticides adsorbed on silica towards T. confusum and T. castaneum was greater than that of formulations containing a mixture of silica and insecticidal dust in terms of the amounts of silica and organic insecticide required for an LC 50, the effect being most pronounced at the lowest wheat moisture content. The potential use of amorphous silica as a carrier for dust formulations of the two insecticides is discussed.