The influence of temperature on yield and quality of carrots were examined using two pot trials
that were conducted in the glasshouse and growth chambers at the Department of Soil, Crop
and Climate Sciences, on the Bloemfontein campus of the University of the Free State in 2009
and 2009/10.
In the first trial the influence of four temperatures (10, 18, 26 and 32°C) on the growth, yield and
quality of two pre-pack carrot cvâs. Nectar and Star 3002 were studied. Carrot seed were sown
in 0.34 m x 0.34 m x 0.35 m pots, filled with topsoil of the sandy loam Bainsvlei form. Pots
were kept in the glasshouse at 20°C (±1°C) for four weeks to allow the seedlings to establish
and reach the first true leaf stage whereupon they were moved to the controlled environment
chambers at different temperatures for 20 weeks. Growth parameters such as leaf number,
plant height and leaf growth were significantly influenced by temperature and all these
parameters performed the best at 10°C at the end of the growth season irrespective of cultivar.
Root fresh and dry mass did not differ significantly between the two cultivars but the affect of
temperature was significant. The highest root fresh mass for both cultivars was also obtained
at 10°C, with âStar 3002â with the highest mass (39.12 g) followed by âNectarâ (34.26 g). Both
cultivars exhibited the highest root dry mass at the lower temperature treatment (10°C) with
âStar 3002â having a higher root dry mass (4.15 g) than âNectarâ (3.87 g). External quality
parameters such as root length and diameter differed significantly between the temperature
treatments and only the length of carrot roots did not differ significantly between the cultivars.
Both âNectarâ and âStar 3002â exhibited the longest roots at 10°C and the shortest roots at
18°C. Root diameter for both cultivars was significantly greater at 10°C than at 18°C. The only
defects observed were green shoulder and misshapen roots. Although not significant, the
percentage green shoulders and misshapen roots were higher at 18°C than at 10°C. Carrots
were significantly firmer at the low temperature (10°C) than at 18°C. The total soluble solid
content of carrots however, grown at 18°C was significantly higher than those grown at 10°C.
In the second pot trial the influence of four dual temperatures (15/5, 24/10, 28/20 and 35/25°C)
on the growth, yield and quality of two pre-pack carrot cultivars âNectarâ and âCS 1006â was
studied. Based on the results of this study, temperature influenced leaf number and plant
height of both cultivars, although not always significantly, during the 32 weeks of growth. Leaf number and plant height of carrot plants were greater at 15/5°C treatment. Yield parameters
and the external quality parameters such as root length; diameter and absence of defects were
also influenced significantly by temperature. Carrot root length and diameter were significantly
influenced positively by lower temperatures (15/5°C) and absence of defects such as green
shoulder and hairiness were significantly influenced negatively by higher temperatures
(28/20°C). Some of the internal quality parameters such as firmness, total soluble solids,
carotene, β-pinene and caryophyllene were also significantly affected by temperature.
Firmness, total soluble solids and carotene were significantly influenced by lower temperature
(15/5°C) whereas β-pinene and caryophyllene were significantly influenced by higher
temperatures (28/20°C).
Free choice profiling (FCP) was carried out in order to investigate how semi-naïve panelists
described and perceived carrot samples cultivated under different temperature conditions. This
method allowed participants to use their own attributes to describe and quantify the food
product. The FCP procedure generated six descriptors on the attribute taste and one on
aftertaste. The two carrot cultivars grown at the higher temperatures (24/10 and 28/20°C) had
descriptors like bitter, sour, bland and chemical, with a definite aftertaste while carrot cultivars
grown at lower temperatures (15/5°C) had descriptors such as sweet and carrot taste
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08152012-150556 |
| Date | 15 August 2012 |
| Creators | Manosa, Nthabiseng Adelaide |
| Contributors | Dr GM Engelbrecht |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08152012-150556/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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