Simple test methods to determine the onset temperatures of viscous flow and caking of spray‐dried amorphous lactose are described. The extent of viscous flow was measured as an increase in the density of lactose plugs within a cylindrical aluminium compaction apparatus after incubation for 3h at a specified temperature. Caking was characterized by an increase in the hardness of the lactose plugs formed. The onset temperature of viscous flow decreased with increasing water activity, Aw, and corresponded to the onset temperature of glass transition, Tg1. Glass transition temperatures were determined using both differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) spin relaxation. The results suggest that elevation of the powder temperature above Tg1 promotes viscous flow and increases the potential for caking of amorphous food powders.

A dipeptidyl aminopeptidase catalysing hydrolysis of X-prolyl amidomethylcoumarin (AMC) substrates has been purified from Lactococcus factis subsp. Zactis H1. The active enzyme has a molecular mass of approximately 150 kDa, a subunit molecular mass of 82 to 83 kDa and is inhibited by the serine protease inhibitor phenylmethylsulphonyl fluoride. The K, and k,,, values for five different dipeptidyl AMC substrates (Gly-Pro-; Leu-Pro-; Lys-Pro-; Phe-Pro-and Glu-Pro-AMC) are similar except for the K , value for Glu-Pro-AMC, which is about threefold higher than that for the other substrates. The enzyme also catalyses hydrolysis of X-Ala-AMC substrates but with much lower k,,, and higher K, values than the corresponding X-Pro-AMC substrates. The pcasein-derived heptapeptides Lys-Ala-Val-Pro-Tyr-Pro-Gln and Tyr-Pro-Phe-Pro-Gly-Pro-Ile were hydrolysed, but bradykinins with N-terminal sequences Arg-Pro-Pro-and Lys-Pro-Pro-were not. Dipeptidyl aminopeptidase specific activity is the same in a plasmid-free strain of L. factis subsp. factis H1 and in the wild-type, indicating that the enzyme is chromosomally encoded.

Summary:The functional properties of whole milk powder (performance during reconstitution in water and coffee) are routinely measured to determine powder quality. An examination of the microstructure of milk powder and of the insoluble material collected after applying a series of functional tests provided insight into why the insoluble material formed during reconstitution.The microstructures (transmission electron microscopy and confocal microscopy) of four commercial whole milk powder samples and of the insoluble material produced during functional testing were assessed. The microstructure of the whole milk powder could be related to features observed in the microstructure of some of the insolubles collected after powder functional testing. It is likely that heating conditions throughout the powder manufacturing process resulted in the denaturation of β-lactoglobulin and its interaction with other proteins and fat globule membrane components, thus influencing the solubility of the milk powder. The application of shear during processing resulted in the greatest change to powder solubility in this study. Increasing homogenisation pressure during processing resulted in fat globule size reduction, adsorption of casein micelles to the fat globule membrane, and the formation of clusters of fat globules caused by the sharing of adsorbed casein micelles. The presence of large numbers of these clusters in the milk powder increased the formation of insoluble material during powder reconstitution in water and coffee.

Predatory insects and spiders are key elements of integrated pest management (IPM) programmes in agricultural crops such as cotton. Management decisions in IPM programmes should to be based on a reliable and efficient method for counting both predators and pests. Knowledge of the temporal constraints that influence sampling is required because arthropod abundance estimates are likely to vary over a growing season and within a day. Few studies have adequately quantified this effect using the beat sheet, a potentially important sampling method. We compared the commonly used methods of suction and visual sampling to the beat sheet, with reference to an absolute cage clamp method for determining the abundance of various arthropod taxa over 5 weeks. There were significantly more entomophagous arthropods recorded using the beat sheet and cage clamp methods than by using suction or visual sampling, and these differences were more pronounced as the plants grew. In a second trial, relative estimates of entomophagous and phytophagous arthropod abundance were made using beat sheet samples collected over a day. Beat sheet estimates of the abundance of only eight of the 43 taxa examined were found to vary significantly over a day. Beat sheet sampling is recommended in further studies of arthropod abundance in cotton, but researchers and pest management advisors should bear in mind the time of season and time of day effects.

Insecticide resistance in Helicoverpa armigera (Hübner) has led to the reduced efficacy of some older insecticide groups (pyrethroids and carbamates) and serious crop losses. Eight small-plot experiments were conducted to evaluate new insecticides for the management of H. armigera in grain crops. Several products showed efficacy equivalent to or better than the commercial standard, thiodicarb. Indoxacarb and spinosad at rates 50% or less of the registered rates for cotton were consistently superior to other tested products across the range of crops treated and provided residual protection for up to 14 d. The insect growth regulator compound, methoxyfenozide, was slower acting than other products tested, but demonstrated potential for H. armigera management. Pyridalyl performed well and warrants further evaluation in grain crops. We discuss the positioning of new compounds in an Insecticide Resistance Management Strategy (IRMS) in relation to a farming system that incorporates both grain and cotton crops. Use guidelines are recommended for indoxacarb, the first new compound to be registered in selected grain crops and cotton in Australia. These guidelines include restricted-use periods and limits on the number of applications per crop. It is anticipated that additional new compounds will be registered in grain crops, leading to the reduced selection pressure on the limited number of efficacious products. Coordinated insecticide use across farming systems and compatibility with developing integrated pest management programs should be fundamental considerations for the future IRMS.