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News Archive > October 2002
Starter Cultures and Media
by Egon Skovmose on Friday, October 18, 2002
Introduction:
Danisco Cultor manufacturer starter cultures and culture media for the food industry. Through a global network (Danlac in North America) Danisco Cultor supplies products to the dairy, meat, backery, fish, vegetable and pharmaceutical industries in more than 100 countries.
Product Range:
Danisco Cultor markets more then 100 types of starter cultures and culture media in various forms(ask for range of cultures and media)
The wide product range contains:
- Mesophilic and thermophilic starter cultures from undefined multiple-species cultures to defined single-strain cultures, for the production yoghurt and other fermented milk products, fresh cheese, soft cheese, semi-hard cheese and hard cheese types and butter. Cultures are also available for meat products and other fermented non-dairy products.
- Culture media and bioactivators to improve the growth and activety of mesophilic and thermophilic bulk starter, and promote production stability and safety.
- Mould cultures, mainly for cheese or sausage ripening.
- Surface ripening and yeast cultures for various cheese types, including red smear cheese, whit mould cheese and Croute Mixte cheese.
- Propionic acid bacteria for the ripening of large-eyed cheese.
- Kefir cultures for fermented milk products.
- Protective cultures to inhibit pathogenic and other undesired bacteria in a variety of dairy and non-dairy products without influencing sensory properties.
- Probiotic cultures as single strains or defined multi-species cultures for dairy and non-dairy applications
Sales Forms And Applications.
by Egon Skovmose on Monday, October 7, 2002
Welcome to Danlac on line store. Our site is secure, meaning Danlac doesn’t have access to your credit card number at any time, only the credit card authorization personnel.
When you shop for a new culture the terminology might differ from what you are used to. e.g. our Visbyvac DIP (direct inoculation) is a direct set culture commonly called Direct Vat Inoculate /DVI.
We offer following:
Visbyvac Bulk 50 - For bulk starter preparation - 10 - 50 liter
Visbyvac Bulk 500 -For bulk starter preparation - 100 - 500 liter
Visbyvac Bulk 1000-For bulk starter preparation - 200 - 1000 liter
Fermovac 1000 -Deep-frozen for bulk starter preparation- 200 - 1000 L
Fermovac 5000 -Deep-frozen for bulk starter preparation- 900 - 5000 L
Pellet DIP - Deep-frozen pelletised cultures for direct set-500-5000 L
Visbyv DIP
(1, 5, 10, 20, 100u) Freeze-dried cultures for direct set- 1 u / 100L
Visbyvac DIP
(1, 5, 10 dose) Freeze dried mould cultures direct set-
Depending on products of application.
Liquid
(1 liter) Liquid special cultures -
Depending on specific culture and product.
VIS-START - Complete culture media for bulk starter - 25 kg. bag.
BIOS 2000
2.5 & 25 kg - Bioactivator to improve a skimmed milk
based bulk starter medium.
Approx. 15 kg / 1,000 L skimmilk
BioCarna Bio Pan
BioVeg Fishflor : Freeze dried non-dairy cultures for
direct incoculation.
Cheese milk and its Suitability for Cheese Manufacturing.
by Egon Skovmose on Friday, October 4, 2002
From experiments, it is clear that milk can be stored for a long time without the S.P.C. count becoming alarmingly high. The limiting factor is not storage time. It is, on the other hand, the selection of the bacteria types under long storage and low temperature, which cause the psychrotrophic bacteria to dominate. They will, in most cases, influence acidity development and cheese quality. The question about how storage of cheese milk influences the quality of the manufactured cheese has been the subject of extensive research. (This work was initiated in the U.S., when farm storage tanks became popular, about 1940)
Trials have shown that storing pasteurized milk and making cheese without further heat treatment resulted in cheese with poor texture. Milk stored raw or thermized (heat-treated) at 65C and then pasteurized before cheese making produces a good textured cheese.
Storing cheese milk at high temperature for a long time e.g. at 8C for longer than 24 hours, normally gives poor results regardless of whether it is raw or thermized milk.
Storing at 4 C for up to 5 days can give tolerable results, but the most stable quality is obtained with thermized milk. Off-flavors can occur in the cheese, because of fat splitting caused by the psychrotrophic bacteria's lipolytic enzymes.
When storing cheese milk for more than 24 hours, it is beneficial for cheese quality to thermize the milk. This process lowers the milk fat's oxidative stability. Therefore, before thermizing, it is necessary to standardize the milk fat to the desired level. Skimming excess fat at a later stage may produce storage problems in other products.
Making cheese from 3-day old milk resulted in a relatively modest yield reduction, while the loss was considerably increased if the milk was stored for 5 days at 4 C or less before making cheese.
The decrease in yield is caused by a drop in recoverable protein. The milk protein under cold storage is attacked by proteolytic enzymes which break down protein into peptides that are not held in the cheese curd.
This is not the only reason for the decreased yield. The cooling process causes an adverse change in the physical-chemical balance by which certain casein molecules travel out of the casein micelles and dissolve in the milk serum phase. Later in the cheese manufacturing process this dissolved casein will escape into the whey.
AD2. MILK SHOULD COME FROM HEALTHY COWS
The cheese-making process is complicated by the fact that there is not always an extensive heat treatment done on cheese milk, e.g. (heat treated 150ºF(65.5C) -16 secs.), so that some pathogenic bacteria may not be destroyed and therefore survive in the cheese.
The Danish Government Dairy Research Plant has, in cooperation with Landbohøjskolens Hygienic-Bacteriological Laboratory, carried out some investigation into this. For the tested bacteria the following temperatures for destruction in 16 seconds have been found:
Staphylococcus aureus 66.4 C
Salmonella typhimurium 66.4 C
Brucella abortus 67.5 C
Mycobacterium tuberculosis 67.5 C
In practice, a safety margin for temperature variation should be in place, as even a slight lowering of the heat treatment temperature increases the chance that the bacteria will survive, the cheese milk should be heat treated to at least 70 C for 16 seconds if we are to be sure that the disease causing bacteria (pathogens) are destroyed
(What are regulations calling for in your area?
AD3. QUALITY OF MILK FOR ACID PRODUCTION:
The milks' quality for acid production is one of the conditions which most affect cheese quality. Lately there has been deterioration in the milk acid production quality. This is possibly because; we now see efficient cooling of the milk. Cooling milk, if it is several days old, affects acid development in cheese making. The Danish Government Dairy research plant says about acid production quality (167 Report):
"There is a tendency for cooled milk to develop acid more slowly than fresh milk, but the difference there might be is so small that in most cases it is not measurable”.
Over-ripening milk can cause a considerable delay in acid formation.
When a starter culture starts ripening and goes further than intended or when there is insufficient cooling of milk by milk producers on the farm, which reflects in poor quality of milk, it has given acid development quality, which is poor and delayed in the cheesevat.
The reason is that such over ripened milk develops acid considerably slower than fresh milk and the formed acid is naturally also present after pasteurization, restricting the lactic acid bacteria, used as the inoculation at the start of cheese making. Plants which store or ripen milk must, therefore, be warned against letting this storage or "ripening" happen at too high a temperature. (Use Lc-Mix FO-01 Visbyvac DIP from the Danlac web store for pre-ripening).
If the titratable acidity increases 0.03-0.04 (e.g. 0.16-0.19) an "over ripening" of the milk will occur and the acid production ability is reduced.
The question about the acid production ability of milk is still unclear as there are many conditions which influence it. The acid production ability in fresh milk from different herds can vary up to 20% from normal. This is caused by cows feed, somatic cell count and the milk solid content.
Other important factors are cleaners and sanitizers, antibiotics and bacteriophage.
Cheese starter should be propagated in a special room where utmost consideration is taken to avoid infection. The cheese make room is the wrong room in which to place the culture tank.
AD. 4 GOOD COAGULATION ABILITY
Cheese milk can have different coagulation abilities and this can be caused mainly by different particle sizes of casein.
The higher the content of Ca++, the bigger the casein particles will be. The bigger the particles are, the better the coagulation ability, as Ca++ form the network, which holds it all together to a solid mass, which we cut with knives.
Particle size also influences the ease by which cheese curd shrinks and releases whey. If they are big, the network is open and coarse, and whey drains more readily.
Different factors influence the content of calcium and phosphate, especially in late lactation milk and milk from diseased animals. Because these minerals are essential to form the network, any abnormality will affect coagulation of the milk. Therefore, avoid such milk where possible in Cheesemaking.
If the milk is stored at low temperatures part of the beta-casein and calcium ions we released from the casein particles, which can explain reduced rennet ability. The reduction is greatest for milk which has been pasteurized prior to being stored.
To compensate for precipitation of calcium, calcium chloride can be added to the milk (up to 20 grams per 100 liters).
If the salt (NaCl) content in the milk is too high, ion exchange occurs, so that the calcium is displaced from casein by sodium, which to some extent decreases the milks' coagulation ability.
AD.5 THE MILK SHOULD BE OF NORMAL COMPOSITION
Normal Composition:
Milk is a colloidal solution in which the fat, protein, lactose and minerals are suspended in water which constitutes up to about 88.0% of the total. Normal milk contains the following range of its constituents:
1. Water 86-88%
2. Milk fat 3- 5%
3. Protein 3- 4% (casein 80 % of protein)
4. Lactose 4.5-5%
5. Minerals 0.7%
It is these components in Cheesemaking which are concentrated to the final cheese (1.10). Milk fat and casein are the main component of cheese, which together with minerals (bridging) and lactose (acid) outlines what the cheese process is all about.
Any variations in milk composition to complete the final product, cheese, are described in the following: "Colostrum Milk"
"Colostrums milk" composition is different from cow to cow as well as day to day. Therefore, there is no rule for the exact time after which the milk must be sent to the plant. When the milk can be boiled without occurrence of precipitation it can be shipped.
"Colostrums milk" coagulates poorly than normal milk and the ability of the cheese curd to release water is not normal. It is not suitable for cheese making. Lactic acid bacteria grow very poorly in such milk. Acid production can be too weak and spoilage of cheese can result. All these things are caused because the milk does not have its normal composition.
Content of Ca+2 is approximately double as in normal milk. Relations between Ca0 and Na20 + K20 are approximately four times greater then in normal milk. In addition, the milk has considerable amounts of albumin and globulin.
Colostrums shouldn't be included in cheese milk as such milk has a very high content of albumin and globulin.
Late Lactation Milk
Milk from late lactating cows has a very poor cheese making ability mostly because of high content of alkaline salts (K- and Na- salts). This gives a colloidal solution where protein is considerably more strongly hydrolyzed than in normal milk. Coagulation and draining of moisture from cheese curd would therefore be proportionally poorer. If the milk has a salty or bitter taste indicating a salt imbalance, it should not be used for cheese. Such milk also is a poor media for desirable bacteria growth and therefore develops acid poorly.
Mastitis Milk
Such milk has a lower casein, calcium and phosphorous content. It gives less yield and has poorer coagulation ability than normal milk.
Milk Total Solids
Economically, it would make sense to select the milk which has the highest protein content and therefore gives the highest cheese yield.
Previously, it was a wide spread perception that in the selection of cheese milk one should prefer the high fat milk (Jersey milk), as according to Research Laboratories in Denmark, it was found that there exists a certain relationship between fat and protein content. In the selection of milk for fat and protein content, a standard ratio fat to protein is required in order to obtain satisfactory cheese. In Holstein cows milk, the ratio between fat and protein is 1.1 - 1.2, while in jersey milk is higher (1.4 - 1.5).
This relationship, in connection with the fact that Jersey milk has a shorter coagulation time and too strong curd (because of the milks' higher buffer action which follows from the higher content of fat free solids), can often cause difficulties in cheese making from Jersey milk.
Water Addition
In order to increase cheese yield water can be added to the milk. The amount of water addition depends on protein content in the milk. Therefore, the addition may occur in the fall when high solid content is present in the milk. The water addition through dilution causes a reduced size of casein particles. It prolongs coagulation time and gives a softer curd which has lost some of its ability to drain whey.
Moisture content in the finished cheese is higher. Sugar content falls as whey will be more diluted by water as well. In the end, the cheese contains more whey than normal.
The result is softer and less sour cheese. Moisture content in the cheese increases by approximately 0.2% and pH by 0.01 unit each time water addition increases by 2% of the amount of milk.
How much water can be added to the milk depends on milk composition as well as the desired moisture content of the final cheese. It is mainly used for soft, less for hard and more for low fat than high fat cheese. Water is sometimes added to the high solid winter milk but is usually not necessary in the summer milk. Some countries use between 0-5% depending on milk composition and cheese curd firmness and matting ability, but water addition should be cautioned and always make sure to use water with high bacteriological standard.
AD.6 MILK SHOULD HAVE GOOD SMELL AND TASTE
Milk can, at milking, already have an unacceptable flavour. This is caused by use of poor feed. If off-flavors from feed have entered the milk it may cause serious defects in the cheese as many of these unpleasant odors and off-flavors can not be removed, even by pasteurization.
Off Flavours have been produced by beets. Sugar beets contain betaine which converts to an evil smelling substance that can enter the milk. This happens if milking takes place 2 to 3 hours after feeding. Also, canola, sweet clover, weeds and moldy feed are highly flavored feeds that must be fed after milking.
Poor smell and taste in milk developed after milking caused by bacteria activity was dealt with earlier. Thus, there is the need to flavour-grade milk prior to accepting it at the plant.
AD.7 FEW BUTYRIC ACID BACTERIA
Judging from tests such as the S.P.C. and thermoduric bacteria count, milk is first grade in most cases. But you must, however ask yourself, is cheese quality not related to this?
When talking about butyric acid fermented cheese, we know which standard should be followed, but with S.P.C. and thermoduric count, we do not get any information about the content of anaerobic spore-forming bacteria.
Individuals not in favor of a test for anaerobic forming bacteria claim that such a test is unnecessary, as just getting a lower total count of bacteria, will show, that the content of anaerobic spore formers is reduced. To prove the above claim that the poorer the milk, the more gas producing anaerobic spore formers present, cheese consultant Aage Rasmussen carried out an experiment.
Weinzirls test was dropped in the U.S. about 1930. Europe still thinks this test is important to detect gas producers.
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