The Clarifying Reagent, or how to make the analysis of milk and dairy products easier
Difficulties with the analysis of opaque milk and dairy products can be resolved by rendering the sample transparent. This allows direct photometric measurements of the reaction mixtures, and all sample pre-treatment steps become unnecessary. For this, several reagents have been reported in literature. Among them, the ‘Clarifying Reagent’ is mainly described here: its composition is given because it is now released from patenting restrictions. Its main property is a low absorbance between 340 and 800 nm. So it can be used in many chemical and enzymatic colorimetric measurements for estimating the quality of milk and dairy products.
Improvement of the ammonia measurement using a clarifying reagent and application to evaluate heat damage in commercial milk samples
Abstract The enzymatic Boehringer procedure for ammonia measurement in milk was improved to be rapid and simple using a clarifying reagent without any pretreatment of the sample. A good correlation ( r =0.99, n =36) existed between the proposed enzymatic method (EM) and the specific electrode method (SEM) when applied on raw and commercial milk samples. The repeatability of the EM applied to UHT milk was satisfactory with a relative standard deviation of 5.4% ( n =26). The EM was used to evaluate heat damage in commercial half-skimmed pasteurised, direct or indirect or unlabelled UHT and in-bottle sterilised milk. The EM was well correlated with absorbance at 340 nm ( A 340 ) of transparent modified milk ( r =0.97, n =42), with lactulose determined by HPLC and by capillary electrophoresis ( r =0.95, n =17 and r =0.95, n =26, respectively). All parameters differentiated significantly ( P A 340 values.
Hill country sheep production. I. The influence of age, flock, and year on some components of reproduction rate in Romney and Border Leicester × Romney ewes.
Data from 7,091 straightbred Romney and Border Leicester × Romney ewes grazed at the Whatawhata Hill Country Research Station over the period 1959 to 1967 have been used to obtain estimates of flock and age-of-ewe effects on reproduction rate and its components and of year-to-year variation. The ewes were from six groups: a Romney control (RCR) flock, a Romney flock in which ewes were mated either to Romney (RER) or to Border Leicester rams (REB), and flocks of first-cross (F1), second-cross (F2), and third-cross (F3) Border Leicester × Romney ewes mated to first-cross Border Leicester × Romney rams. The ewes' ages at lambing varied from 2 to 5 years and no selection was practised. The ratio of number of lambs weaned per ewe present at lambing increased from the RCR (0.84) to the F1 (1.07), then declined with interbreeding to the F2 (0.92) and further to the F3 (0.87) ewes. Similar changes were evident for the percentage of ewes lambing, of multiple births, and of lambs surviving to weaning. Over...