MYCOLOGICAL STATUS OF SOME DAIRY PRODUCTES SERVING IN ASSIUT UNIVERSITY HOSPITALS

MYCOLOGICAL STATUS OF SOME DAIRY PRODUCTES SERVING IN ASSIUT UNIVERSITY HOSPITALS

NAGAH, M. SAAD^* and YASSER, S. WAFY^**

^* Professor of milk hygiene, Faculty of Vet. Med. Assiut University

^** Fellow, Assiut University Hospitals

Email: yasser wafy 2014@yahoo.com

INTRODUCTION

Yoghurt and cheese are very important foods for any person at all stages of life specially patients. So, a great deal of efforts have been made to produce and keep dairy products of good keeping quality.

Yeasts and moulds  not survive pasteurization, so its presence  in dairy products come mainly from re-infection of pasteurized milk during manufacture (Jordral et al., 1993) which come from the environment of factories, air, equipment, water, milk, etc.. (Jay, 1992).

The storage of any milk products in a fluctuated temperature gives a good chance for yeast and mould growth and mycotoxins production which have been associated with several cases of human poisoning of mycotoxicosis (Neal et al., 1998).

At least 200 different types of mould and yeast when growing in certain food, under suitable condition, form a substance that are toxic when eaten (Ibrahim, 2000) they are responsible for many serious diseases of liver, kidney, blood circulation system and blood forming organs (Cole and Cox, 1981), Certain species of yeast constitutes a puplic health hazard in the form of gastrointestinal disturbance, endocarditis and pulmonary infection (Wilson and Plunkett, 1965).

On the other hand, yoghurt and cheese are undesirable even when contain a few fungal numbers of yeasts and moulds as they rapidly grow in it at a wide range of temperature, pH and humidity resulting in objectionable changes that render the product unmarketable (Mossel, 1982).

Likewise, yeasts and moulds in milk and dairy productes might  act as allergen and an irritant to human health (Karthikeyan and Dhanalaksnmi, 2010) and may be the reason for the recent gastrointestinal disease reported in individuals (Irshad et al., 2014).

In hospitals, food serving system quality control is a major management function. As the contamination of yoghurt and cheese with a wide range of yeasts and moulds constitute a great problem for food consumer, therefore this work is planned to secure the prevalence of yeasts and moulds in yoghurt and cheese serving in Assuit University hospitals.

MATERIALS and METHODS

Collection and Preparation of samples

A total of 60 random samples of yoghurt and feta cheese (30 of each) were collected in clean, dry and sterile containers from Food Department in Assiut University hospitals from July to October, 2013.

Each sample was put in an ice tank with thermometer to maintain temp. at 4⁰C. The samples were dispatched to the laboratory with a minimum of delay where they were examined.

Yoghurt:

11 g of the well mixed yoghurt samples were transferred into sterile flask containing 99 ml of sterile 0.1 % peptone water to obtain 1 / 10 dilution (A.P.H.A., 1985).

Cheese (Fete cheese):

11 gram of the well mixed cheese samples were transferred into sterilemortar and thoroughly mashed. 99 ml of sterile 2% sodium citrate solution were added to obtain 1/10 dilution. Ten fold serial dilution up to 10 ^-8 from each sample of yoghurt and cheese were prepared.

Estimation of total yeasts and moulds counts (Harrigan and McCance, 1976):

From the already prepared serial dilutions, duplicate marked plates were inoculated with one ml from each dilution and carefully mixed with 10-15 ml of malt extract agar (containing 500 mg each of chlorotetracycline Hcl and chloramphenicol) tempered at 45 +1⁰C. After solidification inoculated plates were incubated at 25 ⁰C for 5 days of incubation to determine the degree of growth and then repeated on the fifth day. All yeasts and moulds colonies calculated and recorded.

Identification of yeast and mould gnera and species (Moubasher, 1993):

Macroscopical examination: That is carried out by naked eye or by using magnifying hand lens.

Microscopical examination:

By using the wet mount technique a triangular piece of mould colony (4-6 days).

RESULTES

Table 1: Statistical analytical results of yeasts and moulds counts / g of the examined yoghurt and feta cheese samples:

Table 2: Frequency distribution of the examined serving yoghurt and feta cheese samples based on their yeasts and moulds counts / g:

Table 3: Fungal genera and their % of the examined serving yoghurt and feta cheese samples:

DISCUSSION

The summarized results inTables 1, 2&3 showed that only 14 (46.67 %) samples contaminated with yeasts and moulds and their counts / g in yoghurt samples ranged from 2.1 x 10¹ to1.1 x 10³ with an average count of 4.76 x 10² cfu / g. The highest frequency distribution was 6 (42.86%) lied within the range of >10² cfu /g. According to Egyptian Standards (1990), yoghurt must be free from yeasts and moulds, that due to its media which is a good environment for growth, multiplication and mycotoxins production.

The isolates belong to generaAspergillus 3 (12.00%), Penicillium 1 (4.00%), Geotrichum 12 (48.00%) and Monilielle 9 (36.00%). Nearly similar results were obtained by Abuzied and Hammad (2002) and Bahout and Moustafa (2002).

The stipulated results inTables 1,2&3 indicated that only 8 (26.67%) from 30 feta cheese samples contaminated with yeasts and moulds and their counts / gram in feta cheese samples ranged from2.4 x 10¹ to 1.5 x 10³ with an average count of  2.79 x 10²  cfu / g. According to Egyptian standards (2000), cheese must be not contain more than 10 cfu / g yeasts and moulds. The highest frequency distribution was 4(50%) lied within the range of >10² cfu /g.

The isolates belong to generaAspergillus 2 (13.33%), Penicillium 1 (6.67%), Geotrichumb 7 (46.67%) and Monilielle 5(33.33%). Nearly similar results were obtained by EL-shaheer (2013) and Hegazy and Mahgoub (2013). Higher results were obtained by Salih et al. (2012).

The ability of the mould and yeast species to grow at low temperatures and their proteolytic and lipolytic activities (Besancon et al., 1992 and Jakobsen and Narvhus, 1996) may cause spoilage of food by break down their components and liberation of different acids and gases with subsequent change of their odour and flavor and become undesirable and often result in down grading of the product which lead to economic losses (Bouton and Grappin 1995; Beuvier et al., 1997 and EL-Kewaiey et al., 2014).

Likewise, yeast and mold indicator testing is extremely important for determining product freshness and quality, but the current testing process is so long that it can hold up a product’s release for several days.

In general, presence of yeasts and moulds in yoghurt and feta cheese indicate their manufacturing under unsanitary condition and recontamination of pasteurized milk used in manufacturing by workers hand, equipment, utensils and containers or from dust, air and water. Fluctuated temperature given a good chance for growth and multiplication of fungi and secretes toxins which cause the harmful effect to the consumers.

CONCLUSION

In hospitals, milk and dairy products specially yoghurt and cheese are considered the main foods for patients, so that dairy products must be safe, healthy and free from any contamination, specially yeasts and moulds.

So, the following points must be taken in consideration:

Dairy products must be come from dairy processing plant which apply HACCP system in processing, packing, storage and distribution of such products.

Cooling equipment should be fitted with thermograph and cooling monitored by experience personnel.

Avoid presence of dairy products in room temperatures for long time, specially in summer.

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