EVALUATION OF THE HUNTERLAB COLOUR MEASURING INSTRUMENT
Preliminary work done by the Sugar Milling Research Institute (SMRI) showed that the HunterLab colour measuring system could possibly be used to estimate the colour of raw sugar. With this system it was possible to measure the colour within a short time (less than one minute). The instrument (ColorQuest LAV 4S0/0") has been used for several seasons at the Transvaal Sugar Limited Malelane (ML) factory for measuring the colour of brown sugar. Work was also done on refined and C-sugars. This paper summarises the evaluation of this instrument by both the SMRI and ML. Introduction Due to market requirements, ML produces two types of raw sugar, namely light (1000 ICUMSA 420 colour) and dark ( 1 500 ICUMSA 420 colour) and the same equipment (pans, crystallisers, etc.) in the raw sugar factory is used to make the two types of sugar. In order to assist the packaging department personnel to decide which type of brown sugar has to be bagged, a rapid indication of raw sugar colour is required. The thirty minutes required to determine colour by Figure I. the ICUMSA method is too long and it was therefore decided to evaluate instruments that could measure the colour of The spectrally based system is considered to measure 'what sugar "on-line". the eye sccs' and utilises the measurement of three parameThere are a number of instruments available which are suitable for this task (Nielson, 1996 ; Anon, 1996). The SMRI evaluated two HunterLab instruments during 1995 and 1996, namely the Miniscan which is a portable instrument (Dunsmore, 1995) and the ColorQuest LAV 45"/0°, which is a laboratory model, with a view to their suitability for use in the South African sugar industry. The laboratory model was subsequently evaluated by the Malelane factory and used i n the factory during the past three seasons. Description and basis of operation of the ColorQ~iest system The ColorQuest spectrophotometer (Figure 1) is a colour measurement system with a choice of optical sensors depending on the application. Each sensor has its own illumination and viewing geometrics. The system evaluated was the ColorQuest LAV 45"/0°. ters, the tristimulus values. These parameters are represented by three axes, which are illustrated in Figure 2. The vertical axis depicts the lightness "L" of the sample expressed on a scale of 0 to l00 where black = 0 and white = 100, the horizontal axis runs left to right and depicts "a" the redness or greenness, where the redness is positive and the greenness is negative, and the third axis runs from front to back and represents "b", the yellowness (positive), or blueness (negative). In addition, the instrument's software allows these three parameters to be combined and expressed in one of three indices. These are "Z", the brightness index, "WI", the whiteness index and "YI", the yellowness index. The system consists of a sensor and a detector. The sensor uses circumferential illumination, which is provided by a fibre optic ring, to accommodate a variety of samples. Light from the fibres illuminates the sugar sample (400 grams) to be analysed at an angle of 45". The diffused light reflected from the sample is collected at 0" and then directed to a difProc S Afr Sug Teclznol Ass (1999) 73 Evaluation of the HunterLab colour measuring instrument M Moodley, A Dunsmore & L De Jager
of The South Afrcan Sugar Technologists ' Association-June 1982 THE OPERATION AND PERFORMANCE OF CONTINUOUS C-CENTRIFUGALS
A series of factory investigations, initially based on a statistical approach, was carried out to determine the effect of ' various operational parameters on the performance of continuous C-centrifugals. The relationship between C-sugar purity and C-molasses purity is given. The influence of steam and water additions and water temperature on the centrifugal performance is reviewed. The importance of the crystal size distribution of the C-massecuite is discussed relative to its effect on final molasses purity. Introduction The first continuous C-centrifugals were introduced in the South African sugar industry in the late fifties. In about fifteen years they had, because of their many advantages, completely replaced the batch-type centrifugals on Band C-massecuites. During this period many local technologists have investigated the performance of the centrifugals and the findings of Carter,' de R~billard,~ McEvoy and Ar~hibald,~ among others, have greatly contributed to a general improvement in their operation. However, attempts to determine accurately their optimum mode of operation have not been conclusive. This is not surprising, considering the large number of operational variables which are combined in running a centrifugal and the constantly changing characteristics of the massecuite. In Australia, Kirby et a149 6 * 6 and Swindells et a17 have carried out extensive investigations into the performance of continuous centrifugals and have made a series of interesting findings which, however, may not necessarily apply under the different local conditions. In this investigation, carried out over a two season period, a fresh attempt was made to determine the combination of operating conditions which would optimise centrifugal performance. Experimental Approach All the tests were carried but in various factories using C-massecuites as normally supplied to the centrifugal station. The massecuite purity ranged from 47" to 56' at a brix varying between 91" and 95". The curing temperature varied between 58" C and 63" C with viscosities ranging from 500 to 2 600 Pa. s at the curing temperature. The investigation was conducted in four main parts :-(a) A series of factorially-designed experimentss run at factories No. 1, 2 and 3 during the 1980/81 season. The operational variables under investigation were the massecuite throughput, water addition and temperature and steam addition. (b) Six factorially-designed experiments, two each at factories No. 3, 4 and 5, held in June and July 1981. These experiments differed from Part (a) in that they were each carried out in f 6 hours instead of over several days; in addition …
Spatial distribution of root lesion nematodes (Pratylenchus spp.) in a long-term no-till cropping system and their relationship with soil and landscape properties
The Cook Agronomy Farm of Washington State University is a long-term precision agriculture study site. Since 2000, the farm has been in various three-year no-till rotations with winter wheat, spring wheat, and various rotation crops such as barley, canola, peas, lentils, and chickpea. The spatial distribution of root lesion nematodes (Pratylenchus spp.) and their relationships with soil and terrain variables were studied by collecting soil samples at 127 and 124 geo-referenced points in two 12-ha fields during the spring of 2010 and 2011, respectively. Pratylenchus spp. were detected in more than 85% of the sampled locations in both fields. Nematode densities spatially mapped using ArcGIS software occurred in an aggregated pattern. Previous rotation crops had no effect on the spatial distribution. Classification and regression tree analysis (CART) using soil and terrain variables, and nematode density, explained 61 and 34% of the variability associated with nematode density in 2010 and 2011, respectively. Soil edaphic factors, such as organic matter, were stronger predictors of nematode populations than rotation effects.