Microbial Contamination Of Vended Fruit

2.5.3. Cultivation and Harvesting of carrots

Carrots are grown from seeds and takes up to four months to mature but under good environmental conditions varieties of them could mature under 70-80days. They belong to moderately hardy group of plants that are not particularly sensitive to cold and frost. They do best under cool conditions (10°C-25°C) though their seeds could be slow under such conditions too (Elzer, 2014). They also do well in a deep, loose and well drained sandy loam or loam soil that is free of rocks with a pH of 6.3-6.8. Carrots are very sensitive to soil salinity and brackish soils should be avoided (Cunningham, 2000).

Fertilizers that are applied should be applied according to soil type because the carrots require low quantity of nitrogen, moderate phosphate and high quantity of potassium. Here the nitrogen helps to stimulate the leaf growth at the expense of root development and yield and also delays harvesting when it’s added in high quantity; phosphate promotes root development and ensures more vigorous growth while potassium improves the quality of the crop by making it crisper, better coloured roots and still maintains the crop after harvesting. Rocky soils should be prevented to avoid the roots from being hairy (Abbott, 2012).

The harvesting of carrots varies due to the environmental conditions. Under normal environmental conditions, the crop is usually ready for market within 3-3½months but it could take a month longer under cold conditions. The roots are harvested when they reach the desired size but are still tender and succulent. When the tips of the carrots has coloured up properly, the crop is ripe and should be harvested without further delay because further delay can induce cracking of roots which reduces the quality of the crop (Simon et al., 2008).    

2.5.4. Diseases and Pests associated with carrots

There are several diseases associated with carrots that reduce its yield and market value. The common one is the Alternaria leaf blight caused by Xanthomonas carotae. This disease can eradicate a whole carrot plantation. It occurs mainly during the warm, wet weather and causes dark brown spots on the leaves of the crop and brown strips on the petioles. It also causes brown, elongated, horizontal lesions on the roots (Davis, 2004).

White mould caused by Sclerotinia sclerotiorum, which is more common in soft, dense plantings and in cool, wet conditions. It causes a white cottony growth on the above- ground plants of the plant and affects the root which gradually makes the plant tissue soft and watery. Another disease is the Root knot nematodes caused by Meloidogyne species. They cause stubby roots and such attacks are common during hot season that are favourable to the microorganism. Cavity spot caused by Oomycetes Pythium violae and Pythium sulcatum, which results in irregular shape and depressed lesions on the taproots (Davis, 2004). 

Pests such as false wireworms, cutworms, millipedes, red spider mite and aphids damage the roots of this crop. But the pests could be controlled by wide plant spacing, early sowing or harvest, lengthy growth periods and genotype of carrots (Benjamin et al., 1997). While the diseases can be controlled by the use of disease- free seeds, effective crop rotation, deep ploughing, removal and destruction of infected crop residues and prevention of cultivating the crop where these diseases  are prevalent.

2.5.5. Nutritional and Health Benefits of Carots 

Carrot is a root vegetable which contains a small but significant amount of proteins (1.03%), approximately half of that of the potato. Fats are almost completely absent (0.19%) and carbohydrates make up 7.14% of their weight. They are a rather good source of B group vitamins, as well as Vitamins C and E. All minerals and trace elements are present, including iron (0.5mg/100g), they also contain flavonoids, polyacetylenes, all of which possess numerous nutritional and health benefits. 

Three substances stand out in the composition of carrots, they include 

1.    Carotenoids (β-carotene)

This is what the body transforms into Vitamin A for the proper functioning of the retina, particularly for night vision or in low light situations.

2.    Vegetable fibre

Carrots contain about 3%, most of which is in the form of pectin. This helps regulate the transit of stool and soothes the intestinal mucosa

3.    Essential oil

This is active against intestinal parasites.

Benefits of Carrots 

Carrots are beneficial in the following ways:

>    Functions as an Antioxidant, Anti-carcinogen, and Immuno-enhancers:

Like many other coloured vegetables carrot is a gold mine of antioxidants. Carotenoid, poly-phenols and vitamins present in carrot act as anti-oxidants, anti-carcinogens, and immuno-enhancers. Carotenoids widely distributed in orange carrots are potent antioxidants which can neutralize the effect of free radicals (Zhang and Hamauzu, 2004). They have been shown to have inhibition mutagenesis activity contributing to decrease risk of some cancers (Dias, 2012). They also exert anti-carcinogenic activities, reduce inflammatory insult, and modulate immune response.

It was reported that the anti-carcinogenic effect of carrot juice extracts on myeloid and lymphoid leukaemia cell lines. In vitro analysis was done on 72 hours incubation of carrot juice extracts in leukaemia cell lines and non-tumor control cells. It was observed that carrot juice extract possessed the ability to induce apoptosis and cause cell cycle arrest in leukaemia cell lines. The effect was less prominent in myeloid and hematopoietic stem cells. These researchers considered that β-carotene and falcarinol present in the carrot juice extract may have been responsible for this beneficial effect of “kill” leukaemia cells and inhibit their progression (Zaini et al., 2011). 

The immuno-modullatory effect of carrot was carried out by carrot-extracted carotenoid using 24 albino rats. The percentage variation in lymphocytes, eosinophils, monocytes and platelet count was evaluated. Interestingly, carotenoid administered rats showed a significant increase in lymphocytes, eosinoplils, monocytes and platelet concentration. The beneficial effect was due to carrot’s α- and β-carotenoids (Ekam et al., 2006). Carrots help to protect vision, especially night vision and also provide protection against macular degeneration and development of senile cataract, the leading cause of blindness in aged people (Dias, 2012).

>    Possesses Anti-Diabetic, Cholesterol and Cardiovascular Disease Lowering and Anti-Hypertensive properties.

Nutritionists generally recommend eating carrots in moderation because they contain more sugar than any other vegetable. It was shown that there was a significant association between vitamin A-rich carotenoids and diabetes status (Coyne et al., 2005). The research showed how carotenoids level intake decreased the level of glucose intolerance thereby helping diabetic patients manage their condition.
    It was reported that carrots showed cholesterol absorption mitigating effects carried out on carrot-fed rats. It showed a regulation in bile acid secretion, decrease in liver cholesterol and triglyceride level (Nicolle et al., 2003).  The consumption of carrots exerts a protective effect against cardiovascular disease associated with atherosclerosis. This effect may be due to the synergistic action of dietary fibre and antioxidant polyphenols in carrots (Nicolle et al., 2003). Intake of carrots also helps to reduce the risk of heart attacks in women (Gramenzi et al., 1999). 
    The anti-hypertensive effect of carrots was shown by the presence of two cumarin glycosides (DC-2 and DC-3) in carrots. Dose dependent intravenous administration of these glycoside compounds caused a decrease in arterial blood pressure in normotensive anaesthetized rats. It was concluded that the decreased blood pressure observed in in-vitro studies may be due to the calcium channel blocking action of cumarin glycosides (DC-2 and DC-3) from carrots (Gilani et al., 2000).

>    Possesses wound healing properties

It was reported that animals treated with topical cream of ethanolic extract of carrot root, formulated at different concentrations, showed significant decreases in wound area, epithelisation period and scar width when compared to control group animals in an excision wound model. Meanwhile, rate of wound contraction significantly increased. Moreover, there were also significant increases in wound tensile strength, hydroxyproline content and protein content in animals treated with the topical cream formulation of ethanolic extract of carrot seeds. The antioxidant and anti-microbial activities of ethanolic extract of carrot root, mainly flavonoids and phenolic derivates, may be involved in this increased curative property. Wound healing effects may also be due to regulation of collagen expression and inhibition of elevated levels of lipid peroxides (Patil et al., 2012).