MYCOLOGICAL EVALUATION OF MILK AND SOME MILK PRODUCTS IN BENI-SUEF CITY

Assiut University web-site: www.aun.edu.eg

MYCOLOGICAL EVALUATION OF MILK AND SOME MILK PRODUCTS IN

BENI-SUEF CITY

SAADIA H. EL-SHINAWY; ADEL M. EL-KHOLY; ARAFA M.S. MESHREF and

SAMMER W. SHARKAWY

Faculty of Veterinary Medicine, Beni Suef University, Beni-Suef, Egypt

Received: 31 December 2017;       Accepted: 30 January 2018

INTRODUCTION

Milk has been used by human since the beginning of the life  as the mostpopular and nutritious safe human food, this value put the food hygienists in a real challenge, to provide safe  milk to consumer and at the same time keep its nutritional value high as much as possible. In some countries including Egypt, most milk is manufactured into more stable dairy products of worldwide commerce, such as cheese andyoghurt.

The manufactured dairy products from milk have the same properties of original milk moreover; several stages of processing may be unfavorable and add more points of hazard and weakness allowing entrance of molds and unfortunately, these products support molds growth and toxins production due to its contents of protein, low pH and storage under unfavorable conditions Gqaleni et al. (1997); Pardo et al. (2004).

Corresponding author: Dr. SAMMER W. SHARKAWY

E-mail address:ashrykhaled@gmail.com

Present address: Faculty of Veterinary Medicine, Beni Suef University, Beni-Suef, Egypt

Yeasts and molds can grow in milk and its products particulary at suitable conditions of temperature and moisture Barrois et al. (1997). Contamination of these products may occur from the raw material or during the manufacturing, storage and distribution Kure et al. (2004). Such microorganisms influence the biochemical characters and flavor of such products as well as their appearance rendering them commercially undesirable and often resulting in decreasing the grading of the dairy products Muir and Banks (2000).

Mycotoxins produced by certain molds as a toxic substances can be found in dairy products from two origins: indirect contamination, which results when dairy cows ingest feed that contains mycotoxins which pass into the milk such as aflatoxin M1 and direct contamination, which occurs due to the intentional or accidental growth of molds on the surface of the dairy products and  secrete aflatoxins B1, B2, G1 and G2 Sengun et al. (2008) therefore, feeding on a low quality ration contaminated with molds more than 10 cfu /g and kept under humid conditions cause intoxication to both animals and human whom consumed this animal products.

The present work was performed to investigate the presence of molds and yeasts in milk and some milk products in Beni- Suef city, identification of isolated strains and detection of mycotoxins in Rass cheese samples.

MATERIALS AND METHODS

Collection of the samples:

A total of 125 random samples from raw milk, locally manufactured kareish cheese, hard cheese (Rass cheese), plain yoghurt and flavored yoghurt (25 of each) were collected from dairy shops and super markets in Beni-Suef city for mycological and mycotoxicological examination.

Preparation of the samples (A.P.H.A.1992):

Raw milk samples were subjected to storch's test lampert (1975) to exclude all samples proved to be heat treated.

Rass and kareish cheese samples were thoroughly mashed before being emulsified in the diluted solution.

Whole yoghurt samples were perfectly mixed before examination.

Eleven ml or g of each prepared fluid milk and yoghurt samples were added to 99ml of sterile saline to make adilution of 1/10, from which serial dilutions were prepared. In Rass cheese and kareish cheese samples, Eleven grams of prepared samples were aseptically transferred to a sterile blender jar and 99 ml of warmed (40°C) sterile 2% sodium citrate solution were added and the contents were blended till completely emulsified to make a dilution of 1/10 from which decimal dilution were prepared.

Mycological examination (Bailey and Scott, 1978):

From the already prepared serial dilution, one ml was transferred into duplicate petri-dishes and thoroughly mixed with 15 ml of sabaroud dextrose agar containing 50 ppm chloramphenicol Hup and Staddhouders (1972). The inoculated plates were incubated at 25°C for 7 days. The first examination of the plates was done after 3 days to determine the degree of fungi growth. The yeasts and molds count /ml or g was calculated and recorded.

Representative colonies were isolated on the sabaroud dextrose agar slopes which incubated at 25°C for 5 days for further identification.

Isolated molds were identified according to Ramirez (1982); Samson (1979), while yeasts colonies were identified according to lodder (1970).

Aflatoxin M1 in Rass cheese samples was detected by using fluorometerScott and Trucksess, (1997).

RESULTS

Table 1: Statistical analytical results of yeasts and molds Counts in the examined raw milk samples.

Table 2: Statistical analytical results of yeasts and molds counts in the examined Rass cheese samples.

Table 3: Statistical analytical results of yeasts and molds counts in the examined Kareish cheese samples.

Table 4: Statistical analytical results of yeasts and molds counts in the examined large scale yoghurt samples.

Table 5: Incidenceof the identified yeasts isolates.

Table 6: Incidenceof the identified molds isolates.

DISCUSSION

The Results given in Table 1 revealed that the examined milk samples were contaminated with yeasts and molds at percentages of 68% and 64%, respectively with a mean value of 6.22Χ10²± 3.62Χ10²cfu/g and 2.23Χ10²±9.3Χ10¹ cfu/g, respectively. Similar results were reported by Ghazal  (2001), while higher molds and yeasts counts were observed in samples examined by El-Diasty and El- Kaseh (2009); Pešić-Mikulec et al. (2005); Lavoie et al. (2012). The obtained results indicated poor hygiene during handling which might lead to technological problems during processing.

The data summarized in Table 2 revealed that yeasts and molds were isolated from Rass cheese samples at a percentage of 24% and 32% respectively with a mean value of 14±7.21cfu/g and 4.8±1.54cfu/g respectively. Higher counts with lower incidence were reported by Al- Hawary et al. (2002); Amer (2002); El-Asuoty (2011).

The obtained results in Table 3 showed that the count of total yeasts and molds in the examined kareish cheese samples were detected at a percentage of 64% and 60% respectively with a mean value of 3.23×10⁶± 2.017×10⁶ and 1.068×10⁶± 7.20×10⁵ cfu/g. Similar counts were detected by Moawad et al. (2002), while higher counts with lower incidence were reported by Khair-Allah (2000); Hassan (2003), lower counts and incidence were recorded by El-shrief (2000); El-Komy (2002).

The results given in Table 4 proved that the total molds existed in the examined flavored yoghurt samples at a percentage of 24% with a mean value of 2.4 ± 0.87178cfu/g. Higher results for the count were recorded by Moustafa (2004);  Hafez (2010); Hassan (2003).

On the other hand the yeasts failed to be detected in the flavoured yoghurt samples, but both yeasts and molds couldn't be detected in the plain yoghurt samples. The achieved results allow concluding that most of the examined samples proved to be not contaminated with molds and yeasts, which indicate good hygienic measures during production, handling, storage and distribution. The presence of molds in large scale products may be attributed to post pasteurization contamination and/or unsanitary measures during handling and distribution.

Species of Candida pseudotropicalis, Rhodotorula species, Candida species, Torulopsis (candida) glabrata and Cryptococcus neoformans could be isolated from the different samples at varying percentage in Table (5). Several authors obtained the same results as El-Diasty and El- Kaseh (2009); Sarais et al. (1996).

Species of Mucor spp., Asperigellus flavus, Asperigellus niger, Asperigellus fumigatus, Absidia spp., Penicillium spp., Geotrachum candidum, Cladosporium spp., Phoma spp. and fusarium spp. could be isolated from the perivous samples as in Table 6 Several authors obtained the same results El-Diasty and El- Kaseh (2009); Karthikeyan and Pandiyan (2013) and Gulbeand Valdovska (2014).

On the other hand aflatoxin M1 residue couldn^’t be detected in the examined Rass cheese samples. The result is similar to Robinson and tamime (1991); Martins et al. (1995); Škrinjar et al. (2011).

Mold and yeast contamination not only causes deterioration of food but also can adversely affect the health of humans. Moreover, fungi influence the biochemical characters and flavor of the product and its appearance is commercially undesirable and often result in down grading of the product.

It is concluded that strict hygienic measures should be applied during production, processing and distribution of milk and its products to avoid contamination. Periodical inspection must be done by specialists on the dairy farms to minimize milk contamination with different types of yeasts and molds. The milk obtained from dairy animals fed on feedstuffs contaminated with aflatoxin B1 must be rejected. Efficient cleaning and sanitization of farm dairy utensils must be done to improve the quality of raw milk and consequently the related dairy products. Also, monitoring programs should be more extensive with a particular attention in monitoring aflatoxin in milk and milk products. The milk and milk products should be kept under refrigeration and the practice of display at room temperature should be discouraged.

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