THE SCIENCE OF CLEANING OF DAIRY FOULING LAYERS

The science underlying the removal of dairy fouling layers, and particularly the dissolution of proteinaceous deposits in alkaline solution, is relatively poorly understood even though this is a critical feature of many cleaning-in-place operations. We report key results from a series of investigations on heat-induced gels of β- lactoglobulin, the primary whey protein component in milk and whey foulant. These model systems were used to elucidate the reaction behaviour of gels and aggregates whereby the proteinaceous material is converted to a softer, swollen form that can then be removed by fluid shear or diffusion. We show that several features, such as the occurrence of an optimal pH for cleaning, can be related by analogy to the behaviour of synthetic polyelectrolyte polymers. The structure and history of the foulant, pH, ionic strength and salt concentration in the cleaning solution are all shown to be important factors in the chemistry of inter- and intra-molecular interactions explaining why it has been difficult to generalise about the mechanisms involved and to write simple models of their kinetics

FLUID DYNAMIC GAUGING IN DUCT FLOWS – EXPERIMENTS AND CFD SIMULATIONS

The technique of fluid dynamic gauging (FDG) has been developed to measure the thickness of deformable foulant deposits on solid immersed in liquid, in real time and in situ, with a precision of ± 10 micron. Suction is imposed across a gauging nozzle; the flow rate of liquid through the nozzle allows calculation of the proximity of the nozzle to the surface of the deposit. The technique has been demonstrated by Tuladhar et al. (2000) to work well in quasi-static situations, where the bulk liquid is not moving apart from the gauging flow, and in duct flows. FDG in the quasi-static mode has recently been extended by Chew and co-workers (2004a) using computational fluid dynamics (CFD) simulations of the gauging flow fields to allow the forces imposed on the foulant to be estimated, and thereby test its mechanical strength. We term this technique ‘enhanced FDG’. This paper describes the extension of enhanced FDG to simple duct flows, which requires numerical solution of the governing fluid flow equations in the geometries under consideration. The geometry is that employed by Tuladhar et al. (2003), namely a long duct of square cross-section. The experimental results of the present study are compared with the experimental results from Tuladhar et al. (2003) and Chew et al. (2004b). The CFD results of the study are mainly compared with the present experimental results and with the numerical results from Chew et al. (2004a)

Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

Early weaning in Northern Great Plains beef cattle production systems: III. Steer weaning, finishing and carcass characteristics

Studies were conducted to evaluate the effect of early weaning steer calves on BW gain, feedlot performance, and carcass characteristics in two herds located in the Northern Great Plains, USA. Steer calves from predominantly Angus x Hereford dams were stratified within damage and calving date (Fort Keogh Livestock and Range Research Laboratory (LARRL), Miles City, MT, USA; n=354)and randomly assigned to one of three weaning treatments. In addition, steer calves from Angus and Angus x Simmental dams (n=200; Judith Gap (JG), MT, USA) were stratified within breed group by age, calving date, and AI sire. Steer calves either remained with their dams until normal weaning (NW) at approximately 213-d of age or were early weaned at approximately 80-d of age on to one of two early weaning (EW) diets. Steer calves assigned to EW treatments received one of the following diets: (1)17.5% CP (69% RDP and 7.53 MJ/kg NEm); or (2)17.5% CP (57% RDP and 7.69MJ/kg NEm). At time of normal weaning all LARRL steers were gathered and brought into pens at LARRL and held for 22 (2005) or 28-d (2006) before being sold to a commercial feedlot. Sire-identified steers from JG were sent to the University of Illinois for a finishing trial following a 28-d holding period. Steers that were EW were heavier (PPP=0.79) regardless of weaning treatment whereas sire-identified JG steers that received EW treatment were harvested at a younger age (PP=0.05; upper 2/3 choice or better) than NW treated steers (