Microbial and Nutritional Evaluation of Fresh and Wastewater Cultivated Cabbage in Quetta, Pakistan
Abstract
Using wastewater for agricultural irrigation presents potential risks to public health and the environment. The aim of this study was to compare the microbial burden and nutritional components of cabbage grown in fresh and wastewater in Quetta, Pakistan. Cabbage samples randomly collected from fields irrigated with fresh and wastewater sources were analysed for viable bacterial and fungal counts, pH and vitamin contents. There was a significant difference in viable bacterial (3.0 × 106, 1.9 × 107 CFU g-1) and fungal (2.4 × 103, 1.0 × 105 CFU g-1) counts for cabbage grown in fresh and wastewater, respectively. There were no significant differences in pH (7.88/7.86) and contents of the vitamins thiamin (0.31/0.30 mg/100 g), riboflavin (0.05/0.04 mg/100 g), niacin (0.56/.54 mg/100 g), pyridoxine (0.13/0.12 mg/100 g)and ascorbic acid (57.00/56.60 mg/100 g). Results demonstrated that cabbage grown in wastewater had a significantly higher microbial burden than cabbage grown in fresh water, although there were no significant differences in nutritional components of cabbage from the different water sources. These observations emphasise the potential dangers to public health in using wastewater for agricultural irrigation.
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Introduction
Vegetables have high water content and contain valuable nutrients such as carbohydrates, proteins, vitamins and minerals. These vital components are not only necessary for maintenance and buildup of the body but also in maintaining the alkaline reserve of the body (Hanif et al., 2006) and in repairing tissues and preventing various ailments (Bakhsh and Hassan, 2005; Lyaka et al., 2014; Lewu and Kambizi, 2015). An important Brassica vegetable is cabbage (Brassica oleracea), which is an herbaceous flowering plant with leaves forming a compact head and abundantly available in Pakistan for both human and animal consumption. Cabbage is low in calories and a good source of fiber, vitamin A, vitamin C, vitamin B , calcium and 9 iron (Hossain et al., 2016). Brassica vegetables contain active ingredients such as 3,3-diindolylmethane, indole, isothiocyanates and dithiolthiones, which are reported to act as effective modulators to the inherent immune response, and effective anti-bacterial, anti-viral and anti-cancer agents (Zhang et al., 2014).
Consumption of green leafy vegetables has increased in recent years because of their nutritional significance and valuable health effects (Vandekinderen et al., 2008). Cabbage in Pakistanis mostly eaten raw as salad or added to fast foods such as burgers. It is also used as a cooked vegetable. Discarded cabbage as a vegetable by-product can be considered a potential non-conventional feed resource for ruminants. Cabbage may harbor a wide range of microbial contaminants, which undermine their nutritional and health benefits and may result in outbreaks of human infections from ingestion of fresh or minimally treated vegetables (Beuchat, 2002). Use of industrial and domestic effluents to irrigate agricultural land is a usual practice for wastewater disposal in Pakistan (Murtaza et al., 2010; Naz et al., 2016). Recurrent droughts, low rainfall and poorly performing irrigation structure increase water shortage and result in a widespread use of wastewater (Lone et al., 2000). Due to the presence of phosphorous and nitrogen, wastewater is a good source of plant nutrients, however (Nauman and Khan, 2010).
The current study was planned to compare influences of irrigation using freshwater (tube well)and municipal wastewater on the microbial loads and nutritional quality of cabbage.
Conclusion
The results from this study in Quetta, Pakistan demonstrated that cabbage grown in wastewater has a significantly higher microbial burden than cabbage grown in fresh water, although there were no significant differences in nutritional components of cabbage from the different water sources. These observations emphasise the potential dangers to public health in using wastewater for agricultural irrigation. Hence there is a need for regulatory authorities to ensure that wastewater is used for irrigation only after treatment. Further microbiological standards should be established and followed by agriculturalists and sellers for the handling and dispersal of such vegetables. End users are advised to thoroughly rinse such vegetables with clean water before use.
