Coffee milk, also known as evaporated milk or coffee creamer, is a thickened, often sweetened, homogenised and sterilised milk, that is intended for use in coffee. Traditionally, hot boiled milk was added to the coffee to soften its flavour. Using cold milk would cause the coffee to lose too much of its heat. This is where the idea of thickening the milk has sprung from, making it possible to directly add the milk to the coffee. Coffee milk has a thicker texture compared to regular milk, and a higher fat-percentage. Besides whole milk coffee creamer, there is also a semi-skimmed and skimmed coffee milk with a lower fat and sugar content.
Coffee milk production process
Two processes can be distinguished: in-bottle (in-packaging) sterilisation and in-flow (line) sterilisation. In the following paragraph the in-bottle sterilisation process of coffee milk will be discussed more thoroughly, and the in-line sterilisation method will only be discussed briefly.
The raw milk, used to produce coffee milk, should not contain any acids or other metabolic products in high amounts. The germ count must be low, making the milk easier to sterilise. Furthermore, the raw milk should not contain any colostrum, given that this would make the product less heat stable. Using infra-red, the fat and protein content of the raw milk is measured.
In the past, there were legal requirements in the Netherlands, about the the fat and (non-fat) solid content of coffee milk:
- Whole coffee milk: at least 7.5% fat and at least a solid content of 25%
- Semi-skimmed coffee milk: between 4 and 4.5% fat and at least a solid content of 24%
- Skimmed coffee milk: less than 1% fat and at least a solid content of 20%
For this reason, before further processing is carried out, the milk is standardised. Since only water is removed during the evaporation process, the concentrated milk should already have the desired fat to non-fat solid content ratio. Standardisation is achieved by adding skimmed milk (milk, of which a part of the cream has been removed); or sweet buttermilk (a by-product of the butter production); or whey (a by-product of cheese-making), to the raw whole milk, until the desired ratio is obtained.
After standardisation, the milk is intensively pre-heated for about 1-3 min at 100 to 135°C, in a plate or tubular heat exchanger, in order to:
- Kill off pathogenic microorganisms and a large part of the heat-resistant microorganisms and bacterial spores
- Deactivate enzymes
- Increase the heat stability of the evaporated milk
- Reduce the chances of thickening of the evaporated milk when it is stored
- Raise the temperature of the milk in preparation of the first stage of the evaporation installation
- Enhance a certain flavour perception (caramelising the lactose)
The precipitation of the heat-labile protein, from the milk serum onto the casein protein, causes the heat stability of the milk to increase. This serum protein layer prevents the coagulation of the casein micelles during the sterilisation process. In addition, the pre-heating process decreases the quantity of dissolved calcium and phosphate, which has a favourable effect on the heat stability of the product.
After pre-heating the milk is whiter in color, this is due to the fact that the pre-heating causes the serum proteins to denature, and thereby enabling the light to scatter more.
After pre-heating, the milk is cooled to about 70°C.
Using a rotary vacuum evaporator or falling film evaporator, the milk is concentrated down to a solid content of about 31%. Over-concentrating lowers the yield and heat stability of the thickened milk.
By creating a vacuum, the boiling temperature of the milk is lowered to 65 to 70°C, while ensuring that the milk will not get a cooked flavour, and scorching is prevented. A lower temperature results in a risk of thermophilic microorganisms to grow.
In order to prevent the evaporated milk from creaming during long-term storage at a higher temperature, the thickened milk is homogenised with a two-stage high pressure homogeniser. This process takes place under a pressure of 125 to 250 bar, at a temperature of about 60 to 65°C. Homogenisation increases the viscosity, which in turn decreases the heat stability. The Homogenisation should, therefore, not be carried out too intensively. Homogenisation increases the whitening power of the coffee milk in coffee.
After Homogenisation, the milk is cooled to a temperature of 8°C using a heat exchanger. Next, the non-fat solid content of the milk is checked, and if necessary, standardised with water. It is important to note that adding the stabilising salt solution of 10%, causes the milk to dilute again. The milk is then temporarily stored in insulated tanks until the desired amount of stabilising salt is determined.
In order to ensure that the thickened, homogenised coffee milk does not coagulate during sterilisation, a stabilising salt (usually Na2HPO4) is added. Because the stabilising salt is basic, it increases the pH of the coffee milk. In addition, the salt binds a part of the present Ca2+, causing the casein protein to carry a larger negative, repelling charge. Both changes provide an increased heat stability. Since there is a difference between batches of milk, a trial sterilisation is usually performed on small batches to determine the right amount of stabilising salt. After this step, there is the possibility to add additional vitamins to the coffee milk.
After the addition of the stabilising salt, the coffee milk is filled in glass bottles or tin-plated cans. These cans are provided with an internal lacquer layer in order to prevent the iron or tin from ending up in the product. Before the cans are closed off, steam is blown into the upper part of the can (headspace) to limit the over-pressure during the sterilisation process.
The cans and bottles are then sterilised in a rotary autoclave or continuous sterilisation system for 15 to 20 minutes at a temperature of 110 to 120°C. When the desired Sterilising effect has been achieved, the products are cooled down to storage temperature. Through Maillard reactions (caramelising), the coffee milk becomes browner in color. The color can be changed, by applying a different temperature and time combinations. Moreover, sterilisation increases the viscosity of the coffee milk.
The packages are labeled and packed into shipping units. When the coffee milk is stored at a temperature of between 0 and 15°C, it will have a longer shelf life.
The production process for in-flow sterilised coffee milk is similar to that of in-bottle sterilised coffee milk, up until the Homogenisation step. Since in-flow evaporated coffee milk is UHT sterilised, there is no need for intensive Homogenisation. Homogenisation serves in this case only in order to prevent the coffee milk from creaming. After Homogenisation, the milk is cooled to a temperature of between 5 to 8°C and stored temporarily. The Homogenisation step may even be omitted, if the entire process is carried out in one go. Because temporary cold storage tends to increase the risk of further thickening the coffee milk, the latter method is preferred.
The coffee milk is sterilised at a temperature of 122 to 140°C UHT for 4 seconds to 8 minutes with the aid of a tubular heat exchanger. Generally, it is not necessary to add salt to stabilise the coffee milk.
After sterilisation, the coffee milk is aseptically homogenised to reduce any protein aggregates that may have been formed. After the product has been cooled, it can be aseptically filled into various containers. After which, the coffee milk can be stored for 6 to 9 months at room temperature.
Food Safety & Hygienic Design
The preparation area must at least comply with GMP: being visibly clean before use, and no long-term presence of water remaining after cleaning.
Pre-heating is one of two critical steps in the production process to kill off any microorganisms. It is important that this part of the production process is well designed - according to EHEDG-directive no.1. During pre-heating, a plate heat exchanger is often used. It is known that these plates even when new, but even more likely after some time, will start to leak. Regular inspection is key in order to make sure highly deformed thin plates of the plate heat exchanger do not suffer from stress and corrosion in along the splits and cracks.
After pre-heating, the whole line, including filling machine, must be hygienically designed: meaning cleanable to microbial level. Unless the product is pasteurised after filling, GMP is sufficient. The evaporator has to be hygienically designed, because the product is circulated above the evaporator for a longer period of time, and there is a risk of the formation of heat-stable thermophilic microorganisms, which are, at a higher storage temperature (tropical), also able to grow after sterilisation.
However, at GMP, the sterilisation of the packaging is still not a license to be less careful during the pre-processing phase or cleaning the processing equipment less frequently or not fully, or extending the production run. Large amounts of heat-stable toxins, coming from microorganisms, may still be toxic after sterilisation. In particular, toxins of S.aereus can remain, and will pose a threat to consumer health
Soft Drinks Industry Winters
The rich history of Soft Drinks Industry Winters BV is now in its third century. Today, the bottling company is alive more than ever. With a flexible attitude and high quality standards it has become the largest Dutch soft drinks exporter. In addition, the lubricants of Shell Lubricants make the machines run optimally and food safe.
"You ask, Winters fills": that's the motto of Soft Drinks Industry Winters BV in Maarheeze (North Brabant, The Netherlands). The company is not directly known to the consumers: the company has never sold soft drinks under its own name. Still, it can look back on a long and rich history. When William Van Hooff laid the founding stone of his brewery on August 5, 1797, he could not have realised that it would become an international soft drink company in two centuries time. By inheritance to the next generations in the year 1873 Jan Winters came in charge. Since then, the brewery was known by his name. In 1918 the production of soft drinks started. Until 1958 Winters only had regional ambitions. Then the company expanded business and Winters became producer of world renowned branded as Seven-Up, Sunkist and Canada Dry. When the domestic sales of soft drinks stagnated, the sight was set on various foreign markets in the seventies. In 1978 the company became part of TLC Beatrice International Holdings. Together with the Belgian soda bottling Sunco, who belonged to the same group, it took over the French mineral water producer St. Alban in 1996. After a management buyout the holding company Sun Beverages Company emerged in 1998, comprising Winters, Sunco and St. Alban.
In 1989 the licenses for the production of Seven-Up and other branded products for the Dutch market ended. Since then all attention is directed to 'contract filling'. This is done on behalf of major international food companies, retailers and other commercial organizations. Winters fills cans for a range of soft drinks, energy drinks, mixed drinks, juices, waters and beers with well-known brands. Between 5 and 10% of production is destined for its own brands, such as Sun Cola and Orange, Party Cola and Orange, Provita multivitamin drink, Maresca mineral water and Megaforce energy drink. Nearly 95% of the volumes is exported worldwide and thus Winters is immediately the biggest Dutch soda exporter. Every year more than 500 million cans are filled, packed and logistically processed. Winters currently employs 120 people in permanent employment and dozens of seasonal workers. Production runs per working day in three shifts for 24 hours and during the peak season in a four or five shifts.
To realize such large numbers, Winters has three production lines. An important part of each line is the can sealing machine running at very high speeds. Two machines seal 1,200 filled cans per minute and the third will do another 625 units per minute. Frans Cox, head of utilities and engineering projects: "Such devices are very capital intensive. It is very important that they remain in good condition to produce an excellent product with a constant quality. "
For the reliability of the sealing machines the right food grade lubricants are essential. Some parts are lubricated with oil, others with grease. Oils are able to dissipate more heat and are regenerable by filtration. They are applied for the lubrication of (plain) bearings and gears. Fats are oils encapsulated in soap skeleton. They have less heat-dissipating properties, and can not be reused. The fats serve, inter alia, for the lubrication of bearings in hemming rollers. Incidentally, their lubricating frequency is lower than that of oils.
Until ten years ago, Winters used lubricants from various manufacturers. F. Cox: "However, the need hasd arisen to rationalise the diversity of products and providers. To get a better overview, we decided to give one person decision-making authority and to work with just one supplier. The result is that if there are questions, there is only one firm where you can go to the right person. That's an advantage, because of the high speeds the machines are very sensitive and, if necessary, you should be able to rely on a rapid intervention of your lubricant supplier."
Arjan Nieuwstraten, food sector specialist of Shell Lubricants, adds: "The material of a modern beverage can is much thinner than before and therefore the method of sealing is more critical. So you can imagine the tolerances to have to work with will be smaller than before. The importance of the lubrication is thus become much greater. "
At that time Winters already bought around 70% of its lubricants from Shell Lubricants and, partly by this collaboration this supplier was chosen. "The people at Shell were always coming into action directly when needed. They were also always ready for the start up of new equipment, switching to newer oils or fats, assistance in making lubrication schedules, etc. That's why we did not have to think long about who we wanted to go into business with", F. Cox continues.
In practice, there is now a 'gentlemen's agreement' between the two parties. "A synergy has grown between our companies, based on years of trust", A. Nieuwstraten confirms. "The collaboration with Shell Lubricants is closely aligned with the expectations that we have with respect to our suppliers", F. Cox adds.
Incidentally Shell offers Winters an additional service with the Lubriplan software. This lubrication management system provides an accurate overview of the inspection points for fats and oils in the machines and generates user-friendly instructions. So it is indicated where and with what frequency there has to be checked or lubricated and with what product that needs to be done. "Moreover Lubriplan builds up a history of the objects to be lubricated. It may sometimes appear that periodic lubrication at a certain location is needed less frequent than planned. Such cost optimisations we do proactively for Winters", A. Nieuwstraten continues.
In this industry, food safety is of paramount importance and it is essential that no contamination of the filled product occurs. The past decades mineral (engine) oils were used to lubricate can seaming machines. Because these are unfit and improper to come into contact with food, Shell Lubricants has developed a range of food grade oils and fats which are suitable for the lubrication of such equipment. They may be used in the food industry and meet the European standard and the US FDA NSF H1-H1. The FDA (Food and Drug Administration) considers incidental contact of these lubricants with the food product to be acceptable to a level of 10 ppm (parts per million). The lubricants are food safe without compromising on their lubricating properties.
Incidentally, there are two types of food grade products. In some sealing machines the lubrication takes place in a closed circuit: this process is called "recirculating oil '. For such systems Shell Lubricants has developed the synthetic oil 'Shell Cassida Fluid GLE' series. That series has excellent lubricating properties and is recognized by leading suppliers of sealing such as Angelus (USA), FMC FoodTech (Belgium) and Ferrum (Switzerland). A second process is that wherein the lubricant is used only once: the "total-loss system. For this, Shell introduced the food grade mineral oil 'Shell FM Gear Oil TLS 150'. That delivers outstanding performance, even in the presence of water, juice or beer. Moreover, this oil absorbs water, preventing rust.
Remarkable is that these Shell products were developed in cooperation with Soft Drinks Industry Winters. A. Nieuwstraten: "We gave attention both to food security and to the optimization of lubricant performance. At Winter we have gained a lot of knowledge about the lubrication of sealing machines with these products and numerous tests have led to the most sophisticated lubricants for this sector."
Large beverage producers that have known branded products manufactured through contract fillers not only value high the quality of the final product. Also, the extent to which the production process is controlled and hygiene risks are avoided, plays a major role for them. Winters has responded and holds international quality certificates according to ISO 9000, 14001 and HACCP (hazard analysis critical control points). In addition, the bottling company is certified to the BRC standard (British Retail Consortium). That standard contains guidelines which food producers have to meet in order to supply the large English supermarkets. Finally, for German and French retail chains Winters has the IFS certificate (International Food Standard).
With the high quality food grade lubricants of Shell Lubricants and the high quality standards of Winter the consumer profits.
Featured expert: Pieter Van de Schepop