Microbiological profile of hydroponic vegetables grown in ... · Hydroponics is defined as the...
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Microbiological profile of hydroponic vegetables grown in Singapore Song Zheng Qi Tobey, Dr. Saloni Kaur Dang Over the years, there has been a growing demand for foods with better physical and nutritional properties in Singapore as a result of improved education and income growth. However, Singapore, being a small city, relies heavily on imports, perishable foods such as vegetables tend to be less fresh as it takes longer to reach consumers. According to the Agri-Food and Veterinary Authority, 90% of the food consumed in Singapore is imported and only 8% of the vegetables are produced locally (AVA, 2016). Hence, it is necessary to implement alternative farming techniques to ensure food security in Singapore. Hydroponics is defined as the cultivation of plants in nutrient- enriched water with or without the mechanical support of an inert medium such as sand or gravel (Encyclopedia Britannica, 2015). The high nutrient concentration in nutrient solution supports growth of a wide array of microorganisms under hydroponic conditions and can be introduced to growing crops from contaminated irrigation water (Xu and Warriner, 2005). Microorganisms introduced in this manner persists on plants for longer periods as compared to crops cultivated in soil as it infects the interior of the plant instead of the exterior as of those in soil (Settanni et al., 2013). Being a relatively new farming practice, there is limited knowledge on the microbiological safety profile of vegetables grown hydroponically. Conventionally grown Chinese spinach Hydroponically grown spinach Xanthomonas spp. Xanthomonas spp. Erwinia spp. Erwinia spp. Bacillus cereus Bacillus cereus Staphylococcus aureus Staphylococcus aureus Proteus spp. Proteus spp. Acinetobacter spp. Bacillus mycoides Morganella spp. Enterobacter spp. Citrobacter spp. Providencia spp. Klebsiella spp. Different genera = 10 Different genera = 7 Introduction 1. To explore hydroponic farming techniques in Singapore. 2. To establish the safety profile of hydroponic vegetables grown locally by investigating their susceptibility to microbes and its corresponding effect on shelf-life of the produce. Aims Identification of bacterial species Biochemical tests Oxidase test Catalase test Selective media Eosin Methylene Blue Agar MacConkey Agar Mannitol salt agar Bacteria characterisation Gram stain Culture morphology Microbiological profiling by swabbing and growing the cultures on nutrient agar Leaves Stem Sample purchased from local super market Conventionally grown Chinese spinach (Control) Hydroponically grown Chinese spinach Methods • No pesticides and postharvest processing was employed in a local hydroponic farm which could result in a shorter shelf-life. • Generally, there is high bacterial diversity across Chinese spinach from both sources. Fertilizers used during conventional farming might contain manure, harboring more microorganisms. • Common spoilage microorganisms such as Xanthomonas, Erwinia and Bacillus spp. were detected in both Chinese spinach (Sperber et al., 2009). • Most bacteria are enterobacteriaceae and can be eliminated by heat easily. • However, regular food testing should still be conducted to improve the microbiological quality of Chinese spinach sold commercially and to safeguard food security in Singapore. • Future recommendations: o Further biochemical testing is required to characterise bacteria to the species level Discussion Results Figure 1-18. Representative plates of mixed bacteria from swab test of spinach leaves conducted on nutrient agar from day 1, 8 and 23 of purchase respectively, with negative control plates. Plates were incubated at 37℃ for 18 hours. Table 1 . Summary of bacteria identified in both conventionally and hydroponically grown Chinese spinaches AVA (2016) The food we eat Available at: http://www.ava.gov.sg/explore-by-sections/food/singapore-food-supply/the-food- we-eat (Accessed: 5 August 2016) ENCYCLOPEDIA BRITANNICA (2015) Hydroponics Available at: https://global.britannica.com/topic/hydroponics (Accessed: 5 August 2016) Leff, J. and Fierer, N. (2013). Bacterial Communities Associated with the Surfaces of Fresh Fruits and Vegetables. PLoS ONE, 8(3), p.e59310. Seow, J., Ágoston, R., Phua, L. and Yuk, H. (2012). Microbiological quality of fresh vegetables and fruits sold in Singapore. Food Control, 25(1), pp.39-44. SETTANNI, L., MICELI, A., FRANCESCA, N., CRUCIATA, M. & MOSCHETTI, G. 2013. Microbiological investigation of Raphanus sativus L. grown hydroponically in nutrient solutions contaminated with spoilage and pathogenic bacteria. International journal of food microbiology, 160, 344. XU, J. & WARRINER, K. 2005. Coliphage as an indicator of fecal contamination in hydroponic cucumber ( Cucumis sativus L) greenhouses. Journal of the Science of Food and Agriculture, 85, 2397-2400. References Leaf Stem Control Conventional Hydroponic Control Conventional Hydroponic Day 1 Day 8 Day 23
Transcript of Microbiological profile of hydroponic vegetables grown in ... · Hydroponics is defined as the...
Microbiological profile of hydroponic vegetables grown in Singapore
Song Zheng Qi Tobey, Dr. Saloni Kaur Dang
Over the years, there has been a growing demand for foods withbetter physical and nutritional properties in Singapore as a resultof improved education and income growth. However, Singapore,being a small city, relies heavily on imports, perishable foods suchas vegetables tend to be less fresh as it takes longer to reachconsumers. According to the Agri-Food and Veterinary Authority,90% of the food consumed in Singapore is imported and only 8%of the vegetables are produced locally (AVA, 2016). Hence, it isnecessary to implement alternative farming techniques to ensurefood security in Singapore.
Hydroponics is defined as the cultivation of plants in nutrient-enriched water with or without the mechanical support of aninert medium such as sand or gravel (Encyclopedia Britannica,2015). The high nutrient concentration in nutrient solutionsupports growth of a wide array of microorganisms underhydroponic conditions and can be introduced to growing cropsfrom contaminated irrigation water (Xu and Warriner, 2005).Microorganisms introduced in this manner persists on plants forlonger periods as compared to crops cultivated in soil as it infectsthe interior of the plant instead of the exterior as of those in soil(Settanni et al., 2013). Being a relatively new farming practice,there is limited knowledge on the microbiological safety profile ofvegetables grown hydroponically.
ConventionallygrownChinesespinach
Hydroponicallygrown spinach
Xanthomonas spp. Xanthomonas spp.Erwinia spp. Erwinia spp.Bacilluscereus Bacilluscereus
Staphylococcusaureus StaphylococcusaureusProteus spp. Proteus spp.
Acinetobacter spp.BacillusmycoidesMorganella spp.Enterobacter spp.Citrobacter spp.
Providenciaspp.Klebsiella spp.
Different genera=10 Different genera=7
Introduction
1. To explore hydroponic farming techniques in Singapore.2. To establish the safety profile of hydroponic vegetables grown
locally by investigating their susceptibility to microbes and itscorresponding effect on shelf-life of the produce.
Aims
Identificationofbacterialspecies
Biochemicaltests
Oxidasetest Catalasetest
SelectivemediaEosinMethylene
BlueAgar MacConkeyAgar Mannitolsaltagar
Bacteriacharacterisation
Gramstain Culturemorphology
Microbiological profilingbyswabbingandgrowingtheculturesonnutrientagarLeaves Stem
Samplepurchased fromlocalsupermarketConventionallygrown
Chinesespinach(Control)Hydroponicallygrown
Chinesespinach
Methods
• No pesticides and postharvest processing was employed in alocal hydroponic farm which could result in a shorter shelf-life.
• Generally, there is high bacterial diversity across Chinesespinach from both sources. Fertilizers used duringconventional farming might contain manure, harboring moremicroorganisms.
• Common spoilage microorganisms such as Xanthomonas,Erwinia and Bacillus spp. were detected in both Chinesespinach (Sperber et al., 2009).
• Most bacteria are enterobacteriaceae and can be eliminatedby heat easily.
• However, regular food testing should still be conducted toimprove the microbiological quality of Chinese spinach soldcommercially and to safeguard food security in Singapore.
• Future recommendations:o Further biochemical testing is required to
characterise bacteria to the species level
Discussion
Results
Figure1-18.Representativeplatesofmixedbacteriafromswabtestofspinachleavesconductedonnutrientagarfromday1,8and23ofpurchaserespectively,withnegativecontrolplates.Plateswereincubatedat37℃ for18hours.
Table1.SummaryofbacteriaidentifiedinbothconventionallyandhydroponicallygrownChinesespinaches
AVA(2016)Thefoodweeat Availableat:http://www.ava.gov.sg/explore-by-sections/food/singapore-food-supply/the-food-we-eat(Accessed:5August2016)ENCYCLOPEDIABRITANNICA(2015)Hydroponics Availableat:https://global.britannica.com/topic/hydroponics(Accessed:5August2016)Leff,J.andFierer,N.(2013).BacterialCommunitiesAssociatedwiththeSurfacesofFreshFruitsandVegetables.PLoS ONE,8(3),p.e59310.Seow,J.,Ágoston,R.,Phua,L.andYuk,H.(2012).MicrobiologicalqualityoffreshvegetablesandfruitssoldinSingapore.FoodControl,25(1),pp.39-44.SETTANNI,L.,MICELI,A.,FRANCESCA,N.,CRUCIATA,M.&MOSCHETTI,G.2013.MicrobiologicalinvestigationofRaphanussativus L.grownhydroponicallyinnutrientsolutionscontaminatedwithspoilageandpathogenicbacteria.Internationaljournaloffoodmicrobiology, 160, 344.XU,J.&WARRINER,K.2005.Coliphage asanindicatoroffecalcontaminationinhydroponiccucumber(Cucumis sativus L)greenhouses.JournaloftheScienceofFoodandAgriculture, 85, 2397-2400.
References
Leaf StemControl Conventional Hydroponic Control Conventional Hydroponic
Day 1
Day8
Day23
