Guenter Pollach's beet quality discussion (5)

	Processing characteristics of Rhizoctonia-affected sugarbeets.
	M. Bruhns, R. Lemmes and R. Schick jr., Zuckerindustrie (2004), pp. 105-111 (German).

This paper deals with diseased beet, comparable to the "Cambridge paper" of my (former) group, which dealt with Rhizomania-infected beet (published in Zuckerindustrie 1991, pp. 689-700). But the authors did not refer to this paper and did not draw any parallel conclusions.

Although a high invert sugar content of Rhizoctonia infected beet is shown in the tables 1 and 2, the authors conclude the following in section 4 (pp. 110-111):
"Der in befallenen Rüben erhöhte Invertzuckergehalt trägt nur wenig zur Erhöhung des Rohsaft-Invertzuckergehalts bei und kann in der Saftreinigung gut abgebaut werden".
In English: The increased invert sugar content of diseased beet shows little influence on the invert sugar content of raw juice and is well-decomposed during juice purification.

On the other hand, the authors try to explain a drop of thick juice purity, and in section 3.3.2 a purity drop of 4.5 points is mentioned. By making use of figures, given in the tables 5 and 6, more than 3/4 of the purity drop can be explained from the increase in invert sugar (symbols used in the table: S = sugar NS = non-sugar G = glucose F = fructose Q = purity):

Component	From table in the paper	Unit	Tolerant beet	Infected beet	Difference I minus T
S (raw juice)	6	%	7.3	7.4
G (raw juice)	6	%	0.05	0.16
F (raw juice)	6	%	0.03	0.16
G+F		mg/100g S	1096	4324
G+F		mmol/100 g S	6.08	24.0
NS from G+F ^*)		g NS / 100 g S	1.40	5.52	4.12
Purity from this NS ^*)		%	98.62	94.77	-3.85
Purity measured	5	%	95.07	90.13	-4.94
^*) See "Cambridge paper":		NS = (G+F) * 0.23		Q = 10000 / (100+NS)

It seems that very low figures of % G+F, given in table 6 for a rather diluted raw juice from discontinuous laboratory extraction (7.4 % S) were underestimated in their effect on thick juice purity. Therefore a lot of verbal explanations are given in the discussion, which should explain the drop in thick juice purity, but the rather high influence of invert sugar is not mentioned there.

2004-05-12 G. Pollach