Leon the Milkman’s Blog

Problems and defects of cottage cheese: Draft 1

Posted on September 14th, 2009 by Leon the Milkman.
Categories: Dairy News, International Dairy.

The majority of quality problems in cottage cheese are caused by the growth of contaminating bacteria in the cottage cheese. Most contamination comes from the following sources:

• Through the lines of plant, equipment, containers
• Through the wash water(pasteurize wash water where possible)
• Through contact with ambient air
• Through the added dressing
• Through personal contact
• Through additives(herbs must be treated with ethylene or radiated)

Final temperatures should be as close to 0 degrees Celsius as possible and definitely under 4 degrees Celsius.

Please note that a product such as cottage cheese, once packaged, tends to warm up and reach dangerous temperatures very quickly if left at room temperature.

To the contrary, it requires considerable time and energy for cooling by only 10 to 4 degrees Celsius.

It is always best to leave the cottage cheese for 24 hours in storage before shipping, to make sure that the core temperature is low enough to prevent contamination growth.

It is generally recommended that the pH of the cottage cheese be in the range of 5. Below pH5 the cheese tends to have a tart taste, above the micro-pollutants grow too quickly.

Because of the high moisture of cottage cheese, care must be taken since high levels of preservatives like sorbic acid will give off-tastes easily.

Off tastes can be minimized by de-airing the milk before cottage cheese making and by applying MAP gasses into the container top space.

Bitter cheese: Might be poor quality microbial rennet(lots of “side reactions”) or proteolysis from psychrotropic bacteria – these bacteria are usually caused by keeping raw milk on the farm or at the factory for extended periods(2-4 days)

Over-Acid cheese: May result from insufficient washing of the curd, or excessively high temperatures during operations, packaging and storage. Make sure dressing is cold enough before adding to chilled curd. Make sure that the culture used has minimum post-acidification.

Oxidised Taste: Watch out for excessive agitation or other means of including air. Beware of any contact with metal, e.g. copper etc. The main remedy is to change defective cultures (producing peroxide), use quality milk, do keep temperatures at optimum levels throughout the process, avoid product contact with air.

Gel-like texture: Wash water pH or dressing pH too high.

Grittiness: This happens when the curd is cooked too rapidly, or when the granules of curd came in contact with too hot surfaces.

Gumminess or excessive toughness: Excessive cooking temperatures or too high pH. When using the titratable acidity to determine the moment of cutting, the same perceived acidity can result in significant difference of the clot, due to different buffering capacity of milk, or the different effects of lacto-fermentation yeast.

Weak granules: Cooking temperature too low or cut at too high acidity (too low pH on cutting).

Lack of creaminess: Too little dressing or insufficient/irregular mixing of the curd and dressing.

Wheying off: Survival and growth of yeasts. Post-acidification by culture. Insufficient dressing. Proteolysis(may be due to excessive psychrotropes in milk, due to raw milk storage of 2-4 days).

Non-uniformity of curd: The presence of grains of unequal size may be the result of mistreatment of the curd, cutting during cooking, breaking on mixing with the dressing, or packaging. This is remedied by using better equipment, more delicate in their functions and practices of working more smoothly.

Colour defects: May be caused by mold or other contaminants, like from Pseudomonas.

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