Stuart Helliwell

Structure and Pasting Properties of Oat Starch

Following a period of declining food use, oats are now increasing in importance because of perceived nutritional benefits. The pasting properties of oat starch were regarded as similar to those of other cereal starches until the development of instruments with a more rapid mixing system than the amylograph showed characteristic differences in oats. These differences in pasting properties offer opportunities for novel products in both food and industrial areas. The structure, composition, and pasting properties of oat starch are reviewed, with particular emphasis on methods of measurement. Future directions of research in this area are suggested.

Developments in extraction techniques and their application to analysis of volatiles in foods

Abstract Recent developments in analysis of aroma components in foods are reviewed. Aroma compounds are most closely associated with the volatile fraction of foods. Preliminary isolation remains an essential step in such procedures despite rapid developments in measurement techniques. Traditional methods of isolating volatile components have recently been complemented by solid phase microextraction. Gas chromatography (GC) and GC–mass spectrometry (MS) remain the dominant techniques for measurement of the extracted compounds although new electronic noses are promising techniques. Relating the results from instrumental measurements to human perception requires careful control to ensure valid comparisons. The application of multivariate statistics is important in this respect.

Analytical chemistry of chlorpyrifos and diuron in aquatic ecosystems

The chemistry and toxicology of chlorpyrifos and diuron are presented. These compounds represent the extremes of pesticide use both in terms of toxicity and chemistry. Methods used for their determination are reviewed with an emphasis on recent developments in sample preparation and quantification.

Extraction and quantification of chlorophyll a from freshwater green algae

With the refinement of microanalytical methods useful for quantifying plant pigments, the extraction procedure appears to be one of the key steps in chlorophyll analysis. Comparisons of two solvents; methanol and acetone and four methods of extraction; probe sonication, bath sonication, tissue grinding and maceration by mortar and pestle were performed. Using methanol, a probe sonicator was more efficient in chlorophyll a extraction than the other extraction methods (p<0.01). Methanol was the better solvent in all but the maceration method. The maceration method was equally effective for both solvents but was statistically lower (p<0.01) than achieved by methanol and probe sonicator.

Fatty acid composition of lipids of Australian oats

Abstract A method using methanolic sulphuric acid as transmethylating reagent was developed for determining the fatty acid composition of lipids of oats. The method was optimised for reaction conditions and applied to the determination of the fatty acid composition of lipids of a number of varieties of Australian oats grown in several locations. Thirteen fatty acids were detected with oleic, linoleic and palmitic acids comprising more than 95% of the total fatty acids. Total lipid content of the oats was positively related to the proportion of stearic ( r =0·32) and oleic ( r =0·81) acids and negatively correlated with the proportion of palmitic ( r =−0·64), linoleic ( r =−0·39) and linolenic ( r =−0·65) acids. Significant positive correlations were found between total lipid content and absolute content of the major fatty acids ( r =0·67∼0·98), except for linolenic acid ( r =0·12). Environment had significant effects on fatty acid composition, but variety was the controlling factor. The broad sense heritability estimated from individual plot ranged from 69 to 73% and that from the average of three replications and eight locations ranged from 94 to 98% for the major fatty acids. It is possible to improve fatty acid composition of oats by breeding procedures.

Contribution of volatiles to the flavour of oatmeal

Flavour is of direct importance in the acceptance of oatmeals. Panel tests of an oatmeal sample require well-trained panellists and are expensive, time-consuming and difficult. To investigate an appropriate method of sensory testing to be used in a breeding programme, 12 oat samples were processed in the factory and their sensory qualities were assessed by a trained panel. Sensory quality was related to both variety and growing conditions, with variety being the major controlling factor. The volatile profile of the oatmeals was determined by solid phase microextraction using headspace and gas chromatography. Relatively few volatiles were detected in groats, while more than 50 peaks were detected in oatmeals, indicating that most of the volatiles in oatmeals were induced during heat processing. Volatile compounds detected from oatmeals were correlated with the sensory data, and chromatographic peak areas accounted for 43-94% of the variations in sensory attributes. Preliminary identification of volatile compounds showed that the major compounds included hydrocarbons, alcohols, acids and aldehydes. # 2000 Society of Chemical Industry

Toxicity of Bacillus thuringiensis var. israelensis formulations, spinosad, and selected synthetic insecticides to Chironomus tepperi larvae.

ABSTRACT Three Bacillus thuringiensis var. israelensis (BTi) formulations, the bacterial metabolite spinosad, and 7 synthetic insecticides were bioassayed against 4th instars of Chironomus tepperi, a serious pest of rice in southern Australia. The BTi formulations returned 48-h product median lethal concentration (LC50) values (25 ± 1°C) of between 0.59 mg/liter (VectoBac® water-dispersible granule [WDG], 3,000 international toxic units [ITU]/mg) and 2.15 mg/liter (Teknar® suspension concentrate [SC], 1,200 ITU/mg). When LC50 values were adjusted to reflect nominal ITU values of the 3 products, there was still substantial variation, with LC50 values ranging from 1,770 ITU/liter (VectoBac WDG) to 2,580 ITU/liter (Teknar SC). Aquabac® SC (1,200 ITU/mg) showed intermediate activity. Differential activity between formulations may reflect faster settling rates in the more active formulations, which may be a beneficial characteristic when controlling benthic species such as C. tepperi. Spinosad (24-h LC50=28.9 μg active ingredient [AI]/liter) and the synthetic insecticides we evaluated were all substantially more active than BTi. The highest activity was shown by the neonicotinoid compounds thiacloprid, acetamiprid, and clothianidin, which all returned 24-h LC50 values between 1 and 3 μg AI/liter. Indoxacarb and thiomethoxam showed the lowest activity of the synthetic compounds evaluated.

Effects of oat lipids on groat meal pasting properties

The Australian oat cultivar Yarran is unacceptable for human food use due to poor flavour, colour and texture. It has a high lipid content which contains a high proportion of oleic acid. It was compared with an acceptable variety, Mortlock, which has a characteristically lower lipid content with a lower proportion of oleic acid, to study the effect of lipid content on pasting properties of the oat meal. The lipids of both varieties were extracted with petroleum ether and were added back into the defatted meals in sequential amounts. These meals were then tested for viscosity parameters. Both lipid content and composition significantly influenced the meal pasting properties. The peak viscosity and time to peak viscosity were negatively correlated with lipid content whereas setback and pasting temperature increased with increased lipid content. The lipids from Yarran and Mortlock had different effects on the pasting properties. The Mortlock lipid increased the final viscosity (FV) of the defatted meal of Yarran but showed little effect on the FV of its own cultivar. However, the results indicated that the lipid content/composition, although affecting pasting characteristics substantially, were not as important as other meal properties in controlling acceptability for human food use.

Sorption and degradation of fipronil in flooded anaerobic rice soils.

The fate of fipronil in flooded, reductive rice soils was modeled using a conceptual model. Rate constants for the various sorption and degradation processes were calculated from experimental studies involving intact soil cores, and the reductive degradation constant was used to calculate half-lives for fipronil on each soil. The data predicted that fipronil was subject to rapid, reductive degradation or immediate sorption to the soil and any sorbed fipronil desorbed was reductively degraded. The reductive metabolite, fipronil sulfide, accumulated over the 184 day duration of the experiment and sorbed rapidly to the soil, where it accumulated and did not appear to degrade. Neither fipronil nor fipronil sulfide was found beyond the top 1 cm of soil in Yanco soil, while a small amount of each chemical was found up to 4 cm deep in the Coleambally soil profile.

The acute toxicity of fipronil to two non-target invertebrates associated with mosquito breeding sites in Australia

Mosquito-borne arboviruses are a significant health issue in the irrigation areas of south-eastern Australia. Fipronil, a pyrazole insecticide with strong activity against larval Culex species, was tested for its acute effects on Simocephalus elizabethae (Daphniidae) and Polypedilum nubiferum (Chironomidae), two non-target invertebrates associated with Australian rice field mosquito habitats. Technical and formulated fipronil were assessed in the presence or absence of particulate artificial diets in 48 h static bioassays. LC(50) values for neonate S. elizabethae ranged from 11.13 to 19.12 μgl(-1) whilst those for final instar P. nubiferum ranged from 0.89 to 2.18 μgl(-1). Feeding during exposure significantly reduced the susceptibility of P. nubiferum to both technical and formulated fipronil. The effect of feeding was less consistent in Simocephalus bioassays, where much less food was present. We investigated whether adsorption to unconsumed food particles may have limited fipronil bioavailability by using solid-phase microextraction and gas chromatography to measure the available fipronil from fed and unfed systems 24h after establishment. Differences between the systems were not significant (P>0.05). The significantly higher LC(50) values in the fed Polypedilum bioassays do not appear to be a consequence of reduced fipronil bioavailability. Observed differences in toxicity probably reflect increased stresses associated with food deprivation in the unfed bioassays. Our results support published data on the toxicity of fipronil to aquatic invertebrates which suggest that the use of this material as a mosquito larvicide may cause disruption to aquatic ecosystems.