Chemical tests
The links below will provide you with specific information about the chemical tests performed in the CQLab, their procedures and the Seal of Quality Standards.
Procedures for detection of other pathogens such as E.coli 0157, Listeria, Staphylococcus and Clostridium are in development. Please check our web site for more details and ongoing developments.
Please note that all our tests are in compliance with current Macedonian regulations.
Added water in raw milk (Approved by ISO 5764: 2002)
The purpose of this test is to determine if water (either intentionally or accidentally) has been added to milk. When water is added to milk, the concentration of salts and lactose in the milk are diluted. Diluted milk has a higher freezing temperature.
The freezing point of the milk varies subject to various factors such as: season of the year, age of the cow, health and breed of the cow, access to water, the weather, and time of milking. Our laboratory has determined the average freezing point for Macedonia. All results are interpreted using this reference point. The results are recorded as a percentage of added water in milk. If the raw cow milk varies ± 5 % from the reference point, water has been added.
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Seal Of Quality Standards |
Raw milk may not contain added water. The freezing point should be lower than - 0.530°HV
Alkaline Phosphatase test (Approved by NCIMS/ FDA)
The presence of Alkaline Phosphatse, a natural enzyme, indicates that dairy products have not been heated properly (not properly pasteurized), or that the product was exposed to high temperatures after pasteurization (reactivated Phosphatase).
The method used to determine Alkaline Phosphatase dairy products is based on the principle of bio-luminescence and is measured with a bio - luminometer (LUM-T). The results are presented as positive / negative as well as quantitatively through its absolute value.
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Seal Of Quality Standards |
Dairy products:
| Product | mU/L |
| Pasteurized milk | <= 350 mU/L |
| UHT milk | <= 350 mU/L |
Meat products are tested upon request.
Inhibitors and antibiotics in milk (Approved by AOAC 930706; 930707)
Antibiotics
used to treat animal diseases can contaminate food, particularly meat
and dairy product. Depending on the type of antibiotic used the contamination
stays in the animal from a few days to a few weeks. Inhibitors can enter
the milk when equipment is not properly cleaned. The presence of antibiotics
or inhibitors in milk can cause allergic reactions in humans, inhibit
starter cultures, and promote the development of strains bacteria resistant
to antibiotics.
Inhibitor comes from cleaning products.
The QCLab uses the CHR Hansen Test to determine the presence of inhibitors and antibiotics in milk. A bacterial culture is added to the sample. When inhibitors or antibiotics are present bacterial growth is inhibited. The results are recorded as either positive (antibiotics or inhibitors were isolated) or negative (antibiotics or inhibitors were not isolated).
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Seal Of Quality Standards |
All dairy products must be free of inhibitors and antibiotics.
Acidity (Approved by ISO 11869: 1997, ISO 5534: 1985, ISO 5534: 2001, ISO 5547: 1978)
This method can enable us to establish the freshness and shelf life of milk. If milk is not kept in cold storage acidity will increase within a couple of hours. Acidity can also increase when the temperature is low, but more slowly. An increase of acidity occurs as a result of a decomposition of lactose and other components of milk due to the activity of micro-organisms. The acidity of milk reduces the freshness, flavor and quality of milk.
To determine the degree of acidity of dairy products, the Morres method is used, an adaptation of the Soxhlet-Henkel method. The acidity (measured as SH?) indicates the milliliters of 0,1 mol/l sodium hydroxide solution needed to neutralize 20 ml of milk.
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Seal Of Quality Standards |
Dairy products:
| Product | SH° |
| Raw cow milk | <= 7.6 SH° |
| Raw goat milk | <= 7.6 SH° |
| Raw sheep milk | <= 12 SH° |
| UHT milk | <= 7.5 SH° |
| Drinking and set cow yogurt | <= 55 SH° |
| Drinking and set sheep yogurt | <= 65 SH° |
| Sour Cream | <= 64 SH° |
Fat content (Approved by ISO 488: 1983, ISO 11870: ISO 2000, 3432: 1975, ISO 1143: 1973, ISO 11222 1996)
In order to comply the Macedonian Regulation for Quality of Animal Products, products are required to contain a certain fat percentage.
The most common method for determining the fat content is the Acidobutyrometrical method developed by Gerber. The proteins in the product are dissolved using sulfuric acid which separates the fat globules. A butyrometer can then measure the quantity of fat. The results are given as total fats percentage.
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Seal Of Quality Standards |
Dairy products:
| Product | Total Fats % |
| Raw cow milk | >= 3.2% |
| Raw goat milk | >= 3.2% |
| Raw sheep milk | >= 6% |
| Pasteurized milk | >= 3.2% |
| Partially skimmed milk & UHT milk | >= 1.6% |
| Skimmed milk & UHT milk | <= 1.6% |
| UHT milk | >= 3.2% |
| Drinking and set cow yogurt | >= 3.2% |
| Drinking and set sheep yogurt | >= 6% |
| Sour Cream | >= 10% |
| Ice Cream | >= 8% |
| Product | Fat in total solids % |
| Soft white cow cheese | <= 45% |
| Soft white sheep cheese | <= 50% |
| Hard cheese | <= 45% |
| Gouda and Munster | <= 45% |
| Edam | <= 42% |
Meat products:
| Product | Total Fats % |
| Steam cooked sausages | <= 30% |
| Broiled sausages | <= 45% |
| Shelf stabile - for roasting | <= 30% |
| Broiled sausages | <= 30% |
| Broiled sausages from chicken meat | <= 25% |
| Half shelf life sausages from chicken meat | <= 20% |
| Boiled sausages | <= 45% |
| Ham in casing | >= 30% and <= 35% |
| Luncheon meat | >= 30% and <= 35% |
Proteins (Approved by AOAC, AACC 46 14 B)
Proteins are the essential building blocks of the human body. As proteins determine the nutritional value of the milk, it is important that they are above a minimal value.
Our laboratory is using the UDY Protein Analysis System to determine proteins. Weighed samples are mixed with a known volume of Reagent dye solution. Proteins in the sample react with the dye to form a precipitate. The remaining (un-reacted) dye concentration is inversely proportional to the protein content of the sample.
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Seal Of Quality Standards |
Dairy products:
| Product | Protein % |
| Raw cow milk | >= 3% |
| Raw sheep milk | >= 4.3% |
| Raw goat milk | >= 3% |
Meat products
Standards will be developed subsequent to new Macedonian regulation.
pH & Temperature (Approved by the US Standard Method for Examination of Dairy Products)
Controlling the Temperature and pH of meat and dairy products is essential for the safety and quality of the final product. Inadequate control over Temperature and pH can cause food products to spoil and stimulated the growth of micro-organisms.
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Seal Of Quality Standards |
Dairy products:
| Product | pH |
| Fruit Yogurt | >= 3.4 |
| Soft white cow cheese | >= 4.4 |
| Soft white sheep cheese | = 4 |
The acidity of the brine must be the same as the cheese.
All products:
All products must be stored below 4.4°C or below -18°C for frozen products.
Somatic Cell Count in raw milk (DMSCC) (Approved by ISO 133661: 1997)
The somatic cell count (SCC) is commonly used to measure milk quality. Raw milk contains epithelial and white blood cells (somatic cells) and their number are an indicator of the health condition and hygiene of the udder of the cow. High levels of somatic cells indicate a bacterial infection (mastitis) in the animal and result in a reduction in the quality of milk as well as milk yield.
The QCLab used the Direct Microscopic Somatic Cell Count (DMSCC) method as well as the CHARM Soma Lite test to determine the somatic cells present in the sample. The results are recorded as number of somatic cells per ml milk (SCC/ml).
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Seal Of Quality Standards |
Dairy products:
| Product | SCC/ml |
| Raw cow and goat milk | <= 400.000 SCC/ml |
| Raw sheep milk | <= 1.500.000 SCC/ml |
Water activity (Approved by AOAC 978.18 16 th 1995)
The water activity influences the quality, shelf life, and safety of food products as it stimulates the growth of bacteria, yeasts and molds (fungi). The water activity of a food is not the same thing as its moisture content. Although moist foods are likely to have greater water activity than are dry foods, this is not always so; in fact a variety of foods may have exactly the same moisture content and yet have quite different water activities.
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Seal Of Quality Standards |
Meat products:
| Product | Water activity |
| Long shelf life sausages | <= 0.85 |
| Long shelf life whole muscle product | <= 0.85 |
Moisture and total solids (dry substance) (Approved by ISO 6731: 1989, ISO 5534: 1985, ISO 5534: 2001, ISO 1442: 1997)
Determining the moisture and solids of meat products is important as food regulations limit the amount of water that a product may contain. Moisture influences product quality and shelf life as it enhances the growth of micro-organisms.
Dairy and meat products are dried to determine the percentage of moisture and dry substance. Dry substance is defined as components without water and gases. The results are recorded as percentages.
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Seal Of Quality Standards |
Dairy products:
| Product | Dry substance % (without fats) |
| Raw cow milk | >= 8.5% |
| Raw goat milk | >= 8.5% |
| Raw sheep milk | >= 10.5% |
| Pasteurized cow milk | >= 8.5% |
| Pasteurized goat milk | >= 8.5% |
| Pasteurized sheep milk | >= 10.5% |
| Drinking and set cow yogurt | >= 8.5% |
| Drinking and set sheep yogurt | >= 10.5% |
| UHT milk | >= 8.5% |
| Product | Moisture % |
| Soft white cow cheese | >= 50% and <= 55% |
| Soft white goat cheese | >= 50% and <= 55% |
| Sheep | >= 48% and <= 50% |
| Semi hard cheese | <= 42% |
| Other cheeses | <= 55% |
Meat products:
| Product | Moisture % |
| Long shelf life sausages | >= 30% and <= 40% |
| Semi shelf life sausages | <= 55% |
| Cooked sausages | <= 60% |
| Broiled products | <= 60% |
| Luncheon meat | <= 55% |
