Information of the total pigment content of table beet roots is not sufficient enough to estimate their suitability to processing. Differences in the occurrence of the red pigment components of different thermostability determine the mode of processing of the varieties. Pigment extraction methods which require heat treatment (e.g. table beet root powder) need raw materials of higher betanin content.
Of the tested varieties — Bonel, Nero, Favorit, Rubin and Detroit — Bonel and Favorit had the highest betanin content (50.03 and 49.53 mg/100g, respectively).
The isobetanin quantity varies according to varieties (13.10-26.62 mg/100g). Values between 2.92-6.63 mg/100g and 0.96-2.96 mg/100g. respectively were found for betanidin and isobetanidin.
Data revealed the highest BC/BX ratio in the variety Rubin (2.08) indicating good inner colour in sensory tests. However, the high total pigment content (81.01 mg/I00g) was associated with lower betanin content (46,26 mg/100g) and at the same time, with higher isobetanin (25.16 mg/100g), betanidin (6.63 mg/100g) and isobetanidin (2.96 nig/100g) contents. Out of the tested varieties Nero had the lowest total red pigment content (57.43 mg/100g) but the relative betanin value was the highest with nearly 70 %.
Laboratory testing of the table beet root varieties will be required to find the most suitable material to produce colouring agents.
The food industry requires natural colouring agents in increasing quantities. Beet root is highly adapted to this purpose with its red (betacyanin) and yellow (betaxanthin) pigments suitable for numerous products. The two pigments are, however, very heat-sensitive depending not only on the method of drying as well. In our experiment we tested 6 table beet varieties with vacuum drying (instrument: Eurovac KIT-150) and obtained very big differences in the suitability of varieties for drying. The less colour loss was measured in Bordó (16.84%), while Rubin and Cylindra indicated 45.15 and 47.18% loss respectively. During the drying raw material with higher colour content produced higher rate of pigment loss (r = 0.880). In our experiment we found adverse effects on colour material and dry matter content in the fresh beet root. The variety with higher solids (mainly sugar) resulted in higher pigment loss (r = -0.847) during the vacuum drying process. Furthermore, we stated that the yellow pigments (betaxanthin) were less heat sensitive during drying than the red (betacyanin) ones. For the production of beet root powder varieties of high pigment content but low water soluble solids content (sugar) are needed.
Results in table beet breeding (Review)
In our trial morphological and quality parameters of 15 table root varieties were tested at 3 different sowing dates: 15 April, 9 July and 19 August 2010. In the trials the root shape of the varieties form the April sowing date approached most the regular spherical shape (diameter/length –1.0) which is favoured both by fresh market and the processing industry. In the July and August sowings the roots were elongated with reduced proportions. The highest red pigment content (betacyanin) was observed in the second sowing of July (>80 mg/100 g). In the late sowing (August, under plastic tent) a further 10–20 mg/100 g pigment increase was measured in relation to the earlier sowing dates of the same varieties. A similar trend could be observed in yellow pigments (vulgaxanthis) which proves a close correlation between the quantities of the 2 pigments (r=0.823). The highest vulgaxanthin content (103.3–124.18 mg/100 g) was obtained form roots of the late sowing harvested in December. Varieties reacted differently to temperature and so to sugar accumulation in the different sowing periods. In the July sowing higher water soluble solids content was measured on the mean of varieties (10.12 %) as compared to the April sowing (7.76%). Sensory evaluations included inner colour intensity (1–5), with ring (1–3) and taste (1–5) of the raw material evaluated by scoring. According to laboratory measurements better inner colour intensity was observed in the July and August sowing dates. In these samples uniformly coloured, almost with, ring-free roots were obtained. In our trial varieties from the spring sowing had superior taste. Early sowing is recommended for fresh market sale while the second crop (July) harvested in autumn can satisfy processing requirements. In the late sowing (under unheated plastic tent) fresh beet root can be grown at the end of autumn or beginning of winter, thus prolonging the usability of plastic tents.