By P. N. BOYES This paper can be divided into two sections. In
the first, composited weekly samples of molasses have been analysed for certain constituents. The analysis is by no means comprehensive arid those constituents were selected which might affect the viscosity and/or crystallisation, of sucrose. The second is more in the n a t u r e of a progress report dealing with the removal of one of these constituents - starch.
The Analysis of Molasses
Impurities in cane juice affect clarification, crystal- lisation and viscosity of massecuites. The effect of these impurities is obvious to all those working in a sugar house and is reflected in the ease of recovery.
It is well known at Tongaat that, massecuites are
" e a s y " to handle at the beginning of the season and become "difficult" around October/November. The only figures available are the invert sugars and sulphated ash of molasses and the syrup purity.
E a c h of these gives its own seasonal characteristics a n d demonstrate to some extent the observed changes in recovery, viscosity and crystallisation. The words
" g u m , " " w a x " and "glue" are frequently heard but t h e r e have never been any actual determinations of t h e s e quantities at Tongaat. Technologists through- out the world are now aware that certain constituents e.g. amino acids, have an effect out of all proportion to their quantity on crystallisation and viscosity, and it is most important for each mill to be aware of its own major impurities throughout the season. Analy- ses of this type are not abstract pieces of research, since they can be used to analyse constituents in mixed juice and draw attention to poor quality cane, as well as forecasting seasonal difficulties.
Impurities are concentrated in molasses and with samples easily obtained and kept, seemed the obvious source for this investigation. Results of analyses are given in Appendix I expressed as a percentage of dry substance in molasses. It can be seen that the sum- mation of sucrose -[- sulphated ash •)•- invert sugars
-f- gums -!- wax -j- protein gives a figure of about 92 per cent. Due to the nature of the determinations b o t h sulphated ash and protein give a figure which is higher than the actual. The important point is
that tln-se six quantities account for the major portion of the molasses constituents.
In order to observe; trends more clearly, the sucrose was subtracted from the dry substance leaving the non-sucrose per cent in molasses. The impurities were then expressed as a percentage of non-sucrose.
The figures arc; shown in Appendix II. Several sub- stances- soluble silica, P/)-, and K30 show no par- ticular trend over the season, and it is concluded t h a t their influence is constant and they do not contribute towards seasonal trends. Other substances—gums, starch -}- proteins give low figures at the beginning of the season, which increa.se; slightly during the season and show a. sudden jump on the W/E 28/9/57.
This is consistent with factory observation where massecuites increased in stickiness over this period.
It will be seen that proteins show the remarkable increase from a minimum of 6.16 per cent to a maximum of 12.20 per cent. Gums show an increase of 50 per cent and starch 25 per cent.
The wax figures are very much lower than the only other results we have for comparison,9 where the average for July ••{- November molasses samples was 1.1.4 per cent on dry substance in 1956. It can be seen that the wax content was high at the beginning of the season in May and June, dropping to a much lower figure during the middle of the season from July to November and showing some increase towards the end of the season from December to J a n u a r y . The filtration in the experimental procedure is very- slow and it is very noticeable how the rate varies with wax content of the molasses. The 1956 average result for the industry given in Douwes-Dekker's9 report was 0.18 and it can be seen from Appendix I that Tongaat's 1957 figures are sometimes lower.
Since the year, from a recovery point of view, was a good one, it is possible that wax is one of the principal culprits in making our massecuites difficult to handle.
Invert sugars are by far the major constituent of the non-sucroses and demonstrate the well-known characteristic of decreasing as the season progresses and the cane ripens. This year we had the oppor- tunity, by continuing the crushing season into January, of observing the various constituents resorting to their start-of-season values.
43 as on ageing, the starch content of canes tested increased and did not decrease as was assumed in some quarters. In S.M.R.I, tests most starch was found in t h e mature portion of the stalk rather than the green portion. He asked whether in the experi- ments the results of which were reported in Table I I I , a separate control had not been run.
Mr. Boyes replied t h a t this h a d not been done, but from the data presented this could be thrashed out.
From Table IV it could be seen that the clarified juice after treatment contained 40 p.p.m. of starch which would result in a syrup of 1.5(1 p.p.m. Under operating conditions the juice is boiled for three hours and still contains 800 p.p.m. starch in the syrup. Clearly therefore the removal of starch had been affected by something more than heat and floculation and this something was obviously the action of the enzyme.
Mr. Alexander considered that perhaps the same quantity of starch would have been removed by the ordinary defecation treatment under laboratory conditions.
Mr. Hastilow said t h a t last year Mr. Alexander had shown very little correlation between starch content and futrability. He gave a much better correlation when wax andsilicawere compared with filtration rate.
Mr. Rault said t h a t in the days of the Uba Cane it was thought t h a t the poor work at the filter presses was due to t h e high wax content of Natal juices.
He h a d tested samples of filter cakes from various mills as well as from his factory working with carbon- atation. Their wax content was definitely much higher t h a n it is now. The good futrability of carbon- atation sugars, could not be attributed to their freedom from starch, which was detectable in appreciable amounts.
Mr. Johnson asked if Mr. Boyes had found much difference in starch content between the A, B and C Massecuites.
Mr. Boyes referred to Table I, and quoted the figures shown for A and B Massecuites as well as for molasses.
Mr. Alexander said t h a t it was incorrect to suggest t h a t last year's figures proved no correlation between filtrability a n d starch—many other factors could influence this correlation. The influence of only the three impurities, starch, wax and silica, had been considered in tests carried out so far.
Dr. Douwes Dekker said t h a t the figures in the p a p e r would have to be studied and he thought t h a t in time one might be able to draw reliable conclusions from them. The figures affecting filtration are very complicated and this subject was now being studied by the S.M.R.I. He asked Mr. Boyes if he could give a n y indications if the protein content depended on t h e time of the season. He wondered if the type of cane from certain areas was responsible for the sudden j u m p in protein content.
Mr. Boyes said that in 1956 he carried out tests and found t h a t in t h a t season the rise in protein content was more regular, rising as the season pro- gressed. He had no figures to show if t h e protein content depended on the area from which the cane was drawn.
Mr. Rault said the nitrogen or its equivalent pro- tein content of the molasses tested by him from various sulphitation and the one carbonatation factory had seldom shown the present high range of figures, listed in the product of the Tongaat Factory.
He wondered if the clarification by simple lime defe- cation was less effective in removing nitrogenous impurities from cane juice.
Dr. Douwes Dekker said that in recent comparisons simple defecation and sulphitation processes showed no appreciable difference in protein content of molasses.
Mr. Boyes said t h a t he had never been able to reduce the starch content of the syrup in the factory long enough to study the effect on the process. From tests done previously they were not able to find any difference in the starch content of sulphitation as compared with simple defecation.
Dr. Douwes Dekker bore this out.
Mr. Barnes said t h a t in the following paper it was shown t h a t Tongaat was not the biggest offender as far as starch content over all sugar was concerned.
Dr. Douwes Dekker said t h a t if we wished to find correlation between climatic factors and the con- dition of cane it must not be forgotten t h a t there are certain process conditions which would affect t h e starch content of sugars.
Dr. McMartin said t h a t in plants generally reducing sugars were first formed in the leaf during daylight and almost immediately transformed into sucrose and then into starch. During the hours of darkness this was transformed into sucrose and transported down into the stem. This sucrose was usually later transformed into starch because the plant could store more carbohydrate in this form. Some p l a n t s e.g., the potato, h a d special organs, tubers, to enable them to store starch b u t the sugarcane did not h a v e this provision and differed from most plants in storing its carbohydrate as sucrose. It might be t h a t N:Co.310 which had a high sucrose content might simply be a variety with a high carbohydrate manufacturing capacity, and hence high in starch content as well as sucrose. Australia a n d South Africa both produced high sucrose contents a n d these countries had a high starch content; this might be due to the same reason—high capacity for t o t a l carbohydrate manufacture.
Dr. Dick thought t h a t the high starch content recorded for Formosa might be due to t h e popularity there of N:Co.310.