Derechos reconocidos a la unión de hecho

American Society for Nutrition and NAASO, The Obesity Society. Am J ClinNutr. 2005;82:923–934.

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A s i a n J o u r n a l o f

M u l t i d i m e n s i o n a l

R e s e a r c h

( A J M R )

UGC A PPRO VED JO URN AL

MICROBIAL SAFETY OF STREET FOODS IN SELECTED LOCALES OF

COIMBATORE- TAMIL NADU

Suganya.K*; Premala Priyadharshini V **

*Research Scholar *Associate Professor**

Department of Food Service Management and Dietetics, Avinashilingam Institute for Home Science and

Higher Education for Women, Coimbatore, INDIA.

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ABSTRACT

Street food is the ones that are readily available on road side sold on a wheel of cart. Floating population of migrating workers and youngsters forms the main clienteles of this informal food industry. The microbial safety of these foods remains as a cause of concern. With the objective to ascertain the microbial safety of the street vended foods, a ranking on consumers preference of street foods from 200 clienteles selected at random was carried out. A total of 15 highly preferred street foods namely Mushroom, Pani- puri, Masal-puri, Egg fried rice and Vegetable fried rice, Egg Noodles , Vegetable Noodles, Chicken Biriyani, Coconut Chutney, Kara Chutney, Egg omelete, Mathimeen ( (sardine fish fry), Neimeen, (seer fish), Nethilimeen (Anchovies) and Parota were purchased and were tested for microbial contamination by plate method. Characterization and confirmation of pathogen was also tested biochemically. The current paper projects the microbial safety of the five most commonly preferred and sold street foods in the selected locales of Coimbatore. All the five selected street foods street foods were highly contaminated by vibrio cholera and e-coli pseudomonas and staphylococci

KEYWORDS: Street Foods, Microbial Safety Of Foods, Staphylococci, Pseudomonas, E-Coli, Vibrio Cholera, Food Sanitation And Hygiene

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INTRODUCTION

In recent years there has been a notable increase in the consumption of ―street foods‖ by general public. Street foods refers to any light meal eaten between regular meals. Every city, town and village in this vast country of over 1 billion people has its roadside stands and food hawkers. Indians eat street food as breakfast, lunch and dinner, as an afternoon snack (often taken home for ―tea‖), and during festivals when special dishes are prepared.

Street food is made to order and eaten on the spot where the dishes are usually eaten standing or on the move. Food safety of these foods is a major problem because many vendors have no access to clean water or disposal facilities, and often cook and handle food with dirty hands. Street food vendors are often unlicensed, untrained in food hygiene and sanitation, and work under unsanitary conditions1. Recent studies have indicated that ready to eat foods and food preparation surfaces may be reservoirs for microbial contamination. FAO further stipulates that street foods raise concern with respect to their potential for serious food poisoning outbreaks due to improper use of additives, the presence of adulterants, environmental contaminants and improper food handling practices amongst street food vendors2.

Though street food vendors contribute to nations, economic status/ well being, there are also some public health challengers for both urban and rural population3because street foods are readily contaminated from different sources and they increase the risk of food borne disease. World health organization stated that millions of people fall sick or die because of eating unsafe food and therefor food safety has emerged as an important global issue with international trade and public health implications4. Hence the current study titled Microbial safety of street foods in selected locales of Coimbatore was carried out With the objective to ascertain the microbial safety of street vended foods,

METHODOLOGY

Evaluation of Microbial safety on selected street foods i. Selection of food for Microbial Analysis

Based on the findings of the survey on the frequency and commonly consumption of street foods by the customers in the selected locales of Coimbatore, a total of 15 most frequently consumed food items namely Mushroom, Pani-puri, Masal-puri, Egg fried rice and Vegetable fried rice, Egg Noodles and Vegetable Noodles, Chicken Biriyani, Coconut Chutney, Kara Chutney, Egg omelete, Mathimeen, Neimeen,Nethilimeen and Parota were selected for evaluation of microbial safety.

The foods samples were purchased randomly from three out of 107 street food outlets studied comprising five sample from each outlets. The current paper projects the five most commonly consumed and sold street foods namely Parota (Indian bread made out of refined wheat flour.), Vegetable noodles, -Egg fried rice, Vegetable fried rice , Egg noodles .A portion of each street food items was purchased during the peak hours of most patronized time zone. The purchased food items were immediately transferred into a sterile pouch. The sterile pouch with food was kept in a thermocoal box and was taken to the microbial laboratory for analysis.

ii. Preparation of Sample

One gram of solid food sample was weighed by using electronic weighing balance and was transferred aseptically into the mortar and pestle, 10 ml of peptone (diluent) water was added to

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the food sample and it was blended and homogenized for two minutes. The homogenized mixture was filtered using whatsman no -1 filter paper and was transferred into sterile test tube.

iii. Preparation of Nutrient agar / Broth

To a sterilized conical flask with 100ml of distilled water, 0.5g of peptone, 0.5g of Nacland0.3g of Beef extract was dissolved by boiling the mixture under a low flame with constant stirring. The mixture was autoclaved at 121˚C for 15 minutes.

iv. Serial Dilution

A Sterilized test tube was taken, the investigator pipette out nine ml of nutrient broth into it and added one ml of homogenized food sample . The broth was mixed thoroughly and the test tube was marked as dilution 10-1. One ml of sample from dilution 10-1 was pipetted out into a second test tube containing nine ml of nutrient agar , mixed thoroughly and was marked as dilution 10-2 likewise a subsequent dilution till 10-10 was prepared in Laminar air flow chamber . All the 10 dilution were incubated at 37˚C for 24 hours.

v. Preparation of Agar /Medium

To a sterilized conical flask with 150ml of distilled water, 2.20 g of nutrient agar was added and it was dissolved by boiling. The dissolved mixture was mixed thoroughly using a sterile rod and was autoclaved at 121˚C for 15 minutes.

vi. Preparation of plating

Plating was done by spread plate method where 15ml of nutrient medium each was poured in ten sterilized petri plates and was allowed to solidify. The petri plates were marked and named in accordance with food sample and dilution. From each serial dilution of food sample (10 -

1_……10-10

) one ml of diluted food sample was pipetted out and added to the respective plates and was spread using sterile L-shaped rod. The prepared plates were then sealed using paraffin wax and was incubates at 37˚C for 24 hours5

.

vii. Bacterial Count

At the end of the incubation period, the plates with maximum number of colonies were selected and counted by using heamocytometer. Using a Sterile glass rod 0.5ml of food culture were taken into sterile test tube. A drop of trypone blue suspension was added to the test tube containing food culture and mixed well. Using a micropipette ,0.1ml of culture was pipetted out and was place on 4 chambers of heamocytometer and cover slip was placed. Using a microscope the gridlines of the heamocytometerwas focus at 10x objective6.

The total colonies were counted using the formula:

Total colony=Total colonies x Diluent factor = colonies /g

viii. Identification and Characterization of isolates / Bacterial Identification

The isolated colonies of the tested street food samples were then morphologically characterized by gram staining methods to differentiate the presence of bacteria as gram+ve and gram–ve. The principle behind the staining technique is that since the cell walls of gram positive bacteria has a stronger attraction for crystal violet, on application of iodine they retain the crystal violet colour and will remain purple after decolourization with alcohol. Whereas the gram –ve bacteria will be

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colour -less after decolorizing with alcohol and staining with saffranin will make them appear pink7.

ix. Bio-Chemical Tests

After the identification of gram+veand gram-vebacteria, the investigator was interested to identify and confirm the presence of pathogens in the selected street foods by using the following biochemical tests.

a. Catalase Test

To a sterilized glass slide , a drop of culture was placed using a sterilized loop. The glass slide was titled at angle , 3% of hydrogen peroxide was pipetted out and was added to the slide containing the culture. The presence or absence of bubbles formation on the slide was observed. The active reaction in the formation of bubbles indicates the presence of staphylococci and the absence of bubbles confirm the presence of streptococci.

b. Triple iron sugar test

To a sterilized test tube, 6ml of triple iron sugar medium was added. The test tube was tightly closed with a cotton plug and was autoclaved at 121˚C for 15 minutes. The sterilized agar medium was allowed to solidify. The solidified agar was incubated at 37˚C for 24hours and the food culture with maximum colony was added to the bottom of the test tube using a sterile loop and mixed well. The test tube was again incubated at 37˚C for 24 hours. The presence of ferment sugar and hydrogen sulphide gas at the end of the incubation period indicates presence of

Enterobacteriae.

c. Indoletest

To a sterilized test tube 5ml of boiled tryptophan solution was added, using the sterilized loop the test culture was mixed thoroughly with the solution. A few drops of ammonia solution was added into the mixture and 10-15 drops of Kovac‘s reagent wasadded finally. The appearance of cherry red colour ring indicates the presence of E-Coli andVibrio sp. Absence of ring or formation of thin ring indicates the presence of Klebsiella, Salmonella, Shigella spp.

d. Citrate utilization test

To a sterilized test tube 6ml of simmons citrate medium was added. The test tube was incubated at 37˚C for 24 hours. After the incubation period using the sterilized loop the food culture was added into the test tube and again it was incubated at 37˚C for 48hours. At the end of the incubation period, the presence or absence of colour changes was observed. Citrate positive culture was identified by the presence of a blue colour growth on the slant surface of the test tube. Citrate negative will show no growth and the medium will remain green. Convertion of green colourinto deep blue colour indicates the growth of pathogenic microorganisms namely, Klebsiellapneumonia, Enterobacter species, Citrobacterfreundii, Salmonella other thanTyphi and

ParatyphiA,Serratiamarcescens, Proteus mirabilis (minority of strains gives negative result),

Providencia. Absence of colour change (citrate negative test) indicates the presence of

Escherichiacoli, Shigellaspp, SalmonellaTyphi, SalmonellaParatyphiA, Morganellamorganii, and Yersiniaenterocolitica.

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RESULTS AND DISCUSSION