EVALUATION OF SOME FERMENTED MILKS SOLD IN ALEXANDRIA CITY

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

EVALUATION OF SOME FERMENTED MILKS SOLD IN ALEXANDRIA CITY

AHLAM, A. EL LEBOUDY*; AMR, A. AMER*; MARIA, A. EL-ANSARY**;

EL ASUOTY, M.S*** and MARWA, R. AHMIDA****

* Professor of Milk Hygiene, Department of Food Hygiene, Fac. Vet. Med. Alexandria. Univ.

** Lecturer of Milk Hygiene, Department of Food Hygiene, Fac. Vet. Med. Alexandria. Univ.

*** Researcher of Food Hygiene Unit, Animal Health Research Institute, Damanhur branch.

**** Researcher at Department of Food Hygiene, Fac, of Vet, Med, Alexandria, Univ.

Received: 31 May 2017;       Accepted: 25 July2017

INTRODUCTION

The consumption of fermented milks by man dates from the beginning of civilization, once residues of these products were found in pottery fragments from Neolithic Bronze and iron ages settlements in Britain (Mckinley, 2005). Fermented milk products are dairy foods that have been fermented with lactic acid bacteria such as Lactobacillus, Lactococcus and Leuconostoc. The fermentation process increases the shelf-life of the product, while enhancing the taste and improving the digestibility   of   milk.  Various  types  of   fermented

Corresponding author: Dr. AHLAM, A. EL LEBOUDY

E-mail address:mido_15158@hotmail.com

Present address: Professor of Milk Hygiene, Department of Food Hygiene, Fac. Vet. Med. Alexandria. Univ.

milks and derived products have been developed in all parts of the world, each with its own characteristic history. Their nature depends very much on the type of milk used, on the pre-treatment of the milk, on the temperature (climate) and the conditions of fermentation and on the subsequent technological treatments (Tamine and Robison, 2007).

The most common traditional fermented milks are yoghurt, stirred baladi rayeb, sterilized rayeb and Labnah. Yoghurt is a popular fermented milk product consumed in many parts of the world. It is produced in different forms such as whole milk yoghurt, skim milk yoghurt, cream yoghurt, fruit yoghurt and liquid stirred yoghurt (Balasubramanyam and Kulkarni, 1991). It is an extremely popular fermented milk too in Europe, Asia and Africa (Thapa, 2000). Moreover, yoghurt is recommended for sick and convalescent people. Also, it inhibits the bacterial flora of intestine which may lead to constipation, autointoxication and colitis as well as it helps the absorption of calcium and phosphorus (Khan et al., 2008).

Dairy fermented products are liable to contamination with different types of microorganisms from different sources during production, processing and handling, which lead them to be unfit for consumption and constitute a public health hazard (Todaro et al., 2013). Coliforms are routinely used as an indicator to evaluate the quality of milk and milk products as some members of coliforms are responsible for the development of objectionable taints in milk and its products rendering them of inferior quality or even unmarketable (Yabaya and Idris, 2012). Staphylococcus aureus (Staph. aureus)in food article is considered as an index of contamination from personnel sharing in production and handling .Moreover, Staph. aureus is capable of producing several enterotoxins that when ingested through contaminated food could cause food poisoning in human with varying intensity (Brightwell et al., 2006). Enterococcus organisms have a distinctive role as an indicator of poor factory sanitation owing to their relatively high resistance to drying, detergents, as well as freezing temperature. Moreover, these organisms are also implicated in food poisoning outbreaks (Yabaya and Idris, 2012). Fungi usually contaminate fermented dairy products during processing, storage and distribution (Pitt and Hocking, 2009). Yeast is a major cause of yogurt spoilage and other fermented milks in which the low pH provides a selective environment for their growth (Fleet, 1990). Poor hygiene, practiced by handlers of fermented milk products in local markets, may lead to spoilage with pathogenic microorganisms (Tamine and Robison, 2007).

To ensure the safety and quality of fermented milk products consumed at local markets, they must be evaluated by sanitary and microbiological quality and matching with the Egyptian Standards. Therefore, The present study was designed to evaluate some fermented milk products including; plain yoghurt, stirred yoghurt, flavored yoghurt, baladi rayeb, sterilized rayeb and Labnah.

MATERIALS AND METHODS

1. Collection of samples:

A total of one hundred and twenty (120) random samples of locally manufactured fermented milk in the form of plain yoghurt, stirred yoghurt, flavored yoghurt, baladi rayeb, sterilized rayeb and Labnah (20 each) were collected from groceries and supermarkets from various localities in Alexandria city. The collected samples were obtained in their containers as sold to the public or in sterile cups. The samples were dispatched directly to the laboratory of Food Hygiene Department with a minimum of delay in an ice box where they prepared and examined for sanitary and microbiological examination.

2. Methods:

2.1. Determination of titratable acidity of fermented milk samples (AOAC, 1990).

2.2. Microbiological evaluation of the examined prepared samples:

2.2.1. Preparation of fermented milk samples according to (APHA, 1985).

2.2.2. Coliforms count was determined using plate method onto plates of violet red bile agar (Difco) according to the method reported by FDA (2002).

2.2.3. Staphylococcus aureus count (Baird-Parker, 1962).

2.2.4. Enumeration of Enterococci (Deibel and Hartman, 1982).

2.2.5. Isolation and counting of yeasts and molds (Baily and Scott, 1998).

2.3. The obtained results were statistically analyzed by "ANOVA" that was conducting using SAS software (SAS, 2014).

RESULTS

Table 1: Statistical analytical results of titratable acidity percent of the examined fermented dairy products (20 each).

Table 2: Statistical analytical results of coliforms count of the examined fermented dairy products samples (20 each).

*no colonies could be detected on the plates.

Table 3: Incidence % of coliforms isolated from the examined yoghurt samples (20 each).

Table 4: Incidence of coliforms isolated from the examined rayeb samples (20 each).

Table 5: Statistical analytical results of Staph. aureus count of the examined fermented dairy products (20 each).

Table 6: Statistical analytical results of Enterococci count of the examined fermented dairy products (20 each).

Table 7: Statistical analytical results of yeasts count of the examined fermented dairy products (20 each).

Table 8: Statistical analytical results of molds count of the examined fermented dairy products (20 each).

Table 9: Comparison of the obtained results of microbiological evaluation of the examined yoghurt samples with the Egyptian standards (1999) and EOSQC (2005).

*Within: means that the examined samples were within the permissible limit of the Egyptian standards.

**Fail: means that the examined samples failed to conform the Egyptian standards

Table 10: Comparison of the obtained results of microbiological evaluation of the examined Rayeb samples with the Egyptian standards (1999) and EOSQC (2005).

*Within: means that the examined samples were within the permissible limit of the Egyptian standards.

**Fail:  means that the examined samples fail to conform the Egyptian standards.

DISCUSSION

1. Sanitary evaluation of the examined fermented dairy products:

1.1. Titratable acidity %:

The obtained results recorded in Table 1 clarified that the statistical analysis showed that the mean value of the titratable acidity of the examined samples of the fermented milk products under investigation was 0.83±0.007, 0.65±0.01, 0.68±0.011, 0.89±0.005, 0.66±0.01 and 0.14±0.08 %, for plain yoghurt, stirred yoghurt, flavored yoghurt, baladi rayeb, sterilized rayeb and Labnah, respectively. On the other hand higher results were detected by Uzeh et al. (2006) who reported that the total titratable acidity in traditional fermented milk in Nigeria “Nano” was 1.37%.

2. Microbiological evaluation of the examined fermented dairy products:

2.1. Coliforms count:

The presented data in Table 2 showed that coliforms bacteria were detected at an incidence of 50; 0.0; 25; 100; 0.0 and 100%, respectively and the mean value of the coliforms count was 4.10×10²± 20; <10 ; 1.72×10²± 21; 1.65×10³± 2.69×10²; <10 and 6.10×10²± 64 CFU/g, respectively. The recorded results were in agreement with that of Abdel All and Dardir (2009), El-Malt et al. (2013), El-Leboudy et al. (2015), Samet-Bali et al. (2016).

According to the limits proposed by the Egyptian standards (coliforms must be <10 cfu/g), it was noticed that 50 and 25% of the examined samples of the plain and flavored yoghurt, respectively. Failed to comply with the limit (Table 9), and all of the examined samples of baladi rayeb and Labnah failed to comply with the limits (Table 10). While all the examined stirred yoghurt and sterilized rayeb were comply with the limits (Tables 9 and 10).

Higher coliforms count that observed in this study may be attributed to initial contamination of raw milk either from cows, milkers, milk containers and milking environment. In addition, the high number of coliforms in fermented milk provides an index of hygienic standard used in production of milk, as unclean udder and teats can contribute the presence of coliforms from avariety of sources as manure, soil, food, personal and even water (Yabaya and Idris, 2012). Also, Somer and Kilic (2012) noticed that all the yoghurts that were contaminated with coliforms at levels above the acceptable limits, indicating insufficient hygiene process.  

2.2. Staphylococcus aureus count:

It was clear from the findings in Table 5 that Staph. aureus were detected at an incidence of 10, 20, 35, 85, 40 and 100% in the examined samples, respectively. The mean value of Staph. aureus count in the examined fermented samples was 22 ±5; 20± 10; 64± 45; 7.23×10²± 54; 2.1×10²± 21 and 95± 12 CFU/g, respectively. These results were in harmony with that reported by Abdel All and Dardir (2009) who found that the mean Staph. aureus count was 478.2±130 CFU/g. Moreover, El-Leboudy et al. (2015) recorded that the incidence of Staph. aureus was 40% with a mean count value of 92 ±29 CFU/g in the examined samples of plain yoghurt.

According to the limits proposed by the Egyptian standards (Staph. aureus must not be detected), it was noticed that 10, 20 and 35% of the examined samples of plain, stirred and flavored yoghurt, respectively failed to comply with the standard limits (Table 9), moreover, 85, 40 and 100% of the examined samples of baladi rayeb, sterilized rayeb and Labnah, respectively failed to comply with the limits (Table 10). The relatively low counts of Staph. aureus in the examined yoghurt samples may be attributed to the action of yoghurt culture, as it was found that the yoghurt culture reduces the concentration of Staph. aureus added to milk by 1-2 log units during the cold storage of yoghurt (Pazakova et al., 1997).

2.3. Enterococci count:

The data presented in Table 6 clarified that Enterococci were detected at an incidence of 10, 25, 15, 20, 5 and 15% in the examined samples, respectively. The mean value of Enterococci count cfu/g was 1.25×10²± 12; 1.25×10²± 23.2; 1.21×10²± 11; 4.25×10²± 1.97×10²; 22.5± 13 and 1.66×10³± 6.6×10², respectively. This result disagreed with those reported with El-Malt et al. (2013). In addition, El-Leboudy et al. (2015) recorded an incidence of 60 % Enterococci organisms with a mean count of 99.9 ±19.4 CFU/g in the examined samples of plain yoghurt.

2.4. Yeasts count:

The recorded data in Table 7 cleared that yeasts organisms were detected at incidences of 70, 30, 30, 55, 45 and 35 % in the examined samples of fermented milk, respectively. The mean value of yeasts count was 7.87×10⁴± 6.89×10⁴; 5.83×10³± 3.68×10³; 2.16×10³± 6.54×10²; 1.26×10⁴± 3.55×10³; 9.11×10³± 3.82×10³ and 1.28×10³± 0.79×10² CFU/g, respectively. The recorded results were in agreement with Adebesin et al. (2001) who showed that yeasts counts were ranged from 1.0 ×10⁴ to 5.3 ×10⁴ CFU/ml in locally manufactured fermented milk in Nigeria.

According to the limits proposed by the Egyptian standards (yeasts must not be detected), it was noticed that 70, 30 and 30% of the examined samples of plain, stirred and flavored yoghurt, respectively failed to comply with the limits (Table 9). Also, it was noticed that 55, 45 and 35% of the examined samples of baladi rayeb, sterilized rayeb and Labnah, respectively were failed to comply with the standard limits (Table 10).

2.5. Molds count:

The examination for molds is a matter of interest because the mycotoxigenic fungi were able to grow at refrigeration temperature to numbers, which can result in an infection (Potter and Hotchkiss, 1995). Presence of molds in milk and dairy products are undesirable even when found in few numbers as they resulting in objectionable changes that render the products of inferior quality (Abdel Hameed, 2011). Molds and yeasts growing in yoghurt utilized some of the acid and produce a corresponding decrease in the acidity, which may favor the growth of putrefactive bacteria (Oyeleke, 2009).

The presented data in Table 8 cleared that molds were detected at an incidence of 55, 25, 35, 70, 20 and 100 % in the examined concering samples, respectively. The mean value of molds count was 5.88×10⁴± 4.06×10⁴;2.60×10³±1.12×10³; 7.57×10³± 4.72×10³;2.92×10³± 4.38×10²; 3.00×10³± 1.41×10³ and 2.75×10³± 1.12×10³ CFU/g, respectively.  According to the limits proposed by the Egyptian standards (molds count must be <10 CFU/g), it was noticed that 55, 25 and 35% of the examined samples of plain, stirred and flavored yoghurt, respectively failed to comply with the limits (Table 9), and, 70, 20 and 100 % of the examined samples of baladi rayeb, sterilized rayeb and Labnah, respectively failed to comply with the limits (Table 10). The obtained results were in agreement with Shawer (1997) who recorded that mean value of molds count was 3 × l0³ ± 1.35 × 10³ CFU/g.

According to the obtained results of the current study, it could be concluded that the majority of the investigated fermented dairy products that randomly collected from local markets in Alexandria city were contaminated, at a different degrees, with coliforms, Staph. aureus, Enterococci, yeasts and molds giving an indication of poor sanitary measures adopted during manufacturing, storage, handling and distribution of these products. It was concluded and observed that the baladi rayeb and labnah had lower quality than the other examined fermented dairy products. For this reason, increased emphasis should be placed on the microbiology of milk and dairy products. This analysis is critical for the assessment of quality and safety confirmation with standards, specification and regularity compliance.

The application of Hazard Analysis and Critical Control Point (HACCP) as advocated by the WHO should be applied to a wide range of fermented foods in addition to other measures such as use of starter cultures, legislation and educating handlers who prepare such food.

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