Dieser Artikel beschreibt die Grundzüge der Herstellung von Softdrinks, von Rohstoffen und Zubereitung von Sirup bis zur Abfüllung.

Soft drinks

Soft drinks are beverages produced from (mineral) water with sugar or sweeteners. Generally, soft drinks contain carbon dioxide. The carbon dioxide has three functions:

  • It provides a cooling sensation: through the evaporation of the gas heat is extracted from the tongue.
  • It lowers the degree of acidity (pH 2.2 - 3.6), slowing down the growth of microorganism. However, other preservatives may be added in addition.
  • It poisons the air that is possibly present above the soft drink, making it impossible for fungi to grow, due to the lack of oxygen.

If the product does not contain any carbon dioxide, it is considered a ‘flat’ or "still" drink. Additionally, flavourings, fruit- and plant juices, edible parts of fruits or plants and acid are added. Mineral water itself also belongs to the group of soft drinks.

Since the production process is very similar, the term ‘soft’ also applies to value added products, such as energy drinks and isotonic drinks. The market of refreshing beverages based on whey is showing a strong growth. There is also an strong increase visible in the number of ‘light’ soft drinks. Sweeteners are added to these drinks, replacing the sugar and thus lowering the consumers’ calorie intake. Acesulfame, cyclamate, aspartame and saccharin are the only sweeteners allowed.

Soft drinks make up for a large part of the non-alcoholic drinks category.

The Dutch Commodities Act sets a number of requirements for the labeling and naming of soft drinks:

  • Mineral water: Mineral water extracted from a source and bottled at the source.

  • Fruit Lemonade: Whether it is a carbonated beverage or not, with less than 0.5% of alcohol, it has to consist of water, sugar, and between 10 to 25% fermented or non-fermented fruit juices. Only organic acids, flavouring extracts and / or natural aromas are allowed to be added. The sugar, sucrose or glucose level, should be between 7 and 15%. Artificial sweeteners are not allowed.

  • Tonic: The presence of quinine should be indicated on the product label. In addition to a sugar content of more than 5%, the product must contain at least 40 mg of quinine per liter.

  • Lemonade-aerated: A bright, fizzy drink with a sugar content of at least 8%, in which the use of artificial colourings and flavours is allowed. This product does not contain any juice.

  • Caffeinated aerated: The presence of caffeine must be listed on the product label. These products may contain up to 150 mg of caffeine per liter, and may only be manufactured with ortho-phosphoric acid, to a maximum level of 600 mg per liter.

Soft drink production process

Systems for the production of soft drinks generally consist of a storage tank (a silo for the storage of the raw materials such as sugar, colouring and flavouring agents), a water treatment unit, a mixer, a pasteurizer or UHT sterilizer, a system for the adding of carbon dioxide and filling line. All systems can be cleaned automatically, by means of CIP (Cleaning In Place).

Raw materials

Soft drinks mainly consist of water. Due to the possibility of a chemical reaction between the calcium and other minerals in the water, and the colouring and flavouring agents, it may be necessary to soften and filter the water. It is important that the bacterial count of the water is sufficiently low.

  • Drinking water is not free from micro-organisms. By law, the drinking water provided by the water company, must meet the 10 cfu/ml (measured at 22°C) at the supply point of the water company. The absence of organic carbon (clean water) prevents these microorganisms from growing further. As soon as sugar is added, microbial growth is triggered.

Sugar can be supplied in solid or liquid, in syrup form. The flavour of the product is determined by its sweet and sour ratio. For this reason, in addition to sugar, often an acid is added to the product. Next to citric acid, in the production of cola also phosphoric acid may be used.

  • Sugar syrup is microbially stable at 70°Brix. This means that that the sugar content is so high that any microorganisms present cannot withdraw any water from the syrup in order to grow. In fact, the water from the microorganisms themselves is extracted and they dehydrate. A large number of microorganism species do not survive at high concentrations of sugar.

  • However, condensation falling on the sugar syrup allows spores that are present there to grow into living and dividing microorganisms. If a sugar syrup tank is not isolated well, substantial amounts of mildew are found on the surface of the tank.

Syrup Production

The basis of soft drinks, the syrup, is made up of water, sugar, acid, colouring and flavouring agents. This syrup is prepared by dissolving these ingredients into water to 65°Brix.

Sugar can be dissolved in two ways:

  • Warm: dissolving at 70 to 80°C, filtering and cooling to 15°C
  • Cold: dissolving by intensive stirring in cold water, filtering, and pasteurising.

Usually, the sugar is added with a flow meter. With the help of a flow meter with a density measurement (mass flow meter) the sugar content can be measured directly. The density is a measure of the sugar level (also called Brix). The Brix value represents the weight percentage of sugar in the food product. ? In the following table of Oechsle/Brix, the relationship between the density and the Brix value is given.

°Brix Dichtheid bij 20°C °Baumé °Brix Dichtheid bij 20°C °Baumé
1 1.00389 0.56 38 1.16833 20.89
2 1.00779 1.12 39 1.17341 21.43
3 1.01172 1.68 40 1.17853 21.97
4 1.01567 2.24 41 1.18368 22.50
5 1.01965 2.79 42 1.18887 23.04
6 1.02366 3.35 43 1.19410 23.57
7 1.02770 3.91 44 1.19936 24.10
8 1.03176 4.46 45 1.20467 24.63
9 1.03586 5.02 46 1.21001 25.17
10 1.03998 5.57 47 1.21538 25.70
11 1.04413 6.13 48 1.22080 26.23
12 1.04831 6.68 49 1.22625 26.75
13 1.05252 7.24 50 1.23174 27.28
14 1.05677 7.79 51 1.23727 27.81
15 1.06104 8.34 52 1.24284 28.33
16 1.06534 8.98 53 1.24844 28.86
17 1.06968 9.45 54 1.25408 29.38
18 1.07404 10.00 55 1.25976 29.90
19 1.07844 10.55 56 1.26548 30.42
20 1.08287 11.10 57 1.27123 30.94
21 1.08733 11.65 58 1.27703 31.46
22 1.09183 12.20 59 1.28286 31.97
23 1.09636 12.74 60 1.28873 32.49
24 1.10092 13.29 61 1.29464 33.00
25 1.10551 13.84 62 1.30059 33.51
26 1.11014 14.39 63 1.30657 34.02
27 1.11480 14.93 64 1.31260 34.53
28 1.11949 15.48 65 1.31866 35.04
29 1.12422 16.02 66 1.32476 35.55
30 1.12898 16.57 67 1.33090 36.05
31 1.13378 17.11 68 1.33708 36.55
32 1.13861 17.65 69 1.34330 37.06
33 1.14347 18.19 70 1.34956 37.56
34 1.14837 18.73 71 1.35585 38.06
35 1.15331 19.28 72 1.36218 38.55
36 1.15828 19.81 73 1.36856 39.05
37 1.16329 20.35 74 1.37496 39.54

When instead of sugar, sweeteners are added, the required sweetness is determined through measuring the electrical conductivity of the solution. Measuring the density will not give accurate results due to the low density change of the solution.

The order in which the other ingredients are added varies per recipe. The colouring and flavouring agents and acids are usually only added in low concentrations, and are easy to dose by hand or by dosing pumps. When fruit juices are added to the syrup, the product should be pasteurised before impregnation.

The syrup must be given time to settle, so that any air whipped in can escape. This can also be done by using a vacuum deaerator: a rotating disc or plate over which the liquid (syrup) flows, while the surrounding space is continuously maintained under vacuum. It is also possible to bottle the syrup undiluted. Consumers can dilute the syrup themselves at home and optionally add carbon dioxide.


Syrup with fruit juices or with a pH of 3 or higher must be pasteurized at 80°C for 20 seconds before impregnation. This temperature is sufficient to kill off all living, vegetative cells. Only the spores, a survival mode for a number of species of microorganisms, may still be left behind. As long as the pH is lower than 4.6, they cannot develop into vegetative cells, which can grow further. If the pH turns out to be higher than 4.6, then the product must be sterilised or has a limited shelf life under refrigerated conditions.


Impregnation is the process of mixing water with carbon dioxide. The solubility of carbon dioxide gas in water depends on the pressure and the temperature of the water. The colder the water, the higher the solubility.

Carbon dioxide, however, is more soluble in air than in water. A balance will occur between the carbonic acid in the water and the carbon dioxide in the air. In a vacuum boiler the water is de-aerated as much as possible. After that the water is impregnated with carbon dioxide under high-pressure.

Mixing the syrup and the carbonated water can be done in 3 ways:

  • Premix-method: In this method, two separate filling systems are needed, because the syrup is filled into the bottle before the carbonated water is added.
  • Trimix or Intermix System: With this system, the carbonated water and the syrup are mixed in the proper ratio by using metering pumps.
  • Mixing In-line: During the pumping of the syrup, water is added in-lin. With a static mixer in the pipeline, the solution is mixed well. Checking if the correct mix ratio is achieved can be done by measuring the density of the solution. Subsequently, the in-line impregnation process takes place. After impregnation, the solution is mixed again by a static mixer.

Bottling process

The majority of soft drinks are filled under pressure into bottles (glass or PET) or cans, achieving a maximum CO2-content of 8 grams. After filling, the bottles are immediately closed off with a (sterile) crown cap or a cap with plastic layer. In order to prevent airborne infections, often sterile air is blown over the bottle opening. Sometimes block packaging is applied.

The final step of the bottling process is labeling the packages with a labeling machine.

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.

The syrup tank is seldom or never cleaned because of the supposed shelf life. As long as there is no mould growth, this is acceptable. The top of the tank - including manhole and air vent - must be heated and isolated for that purpose.

Pasteurisation is the critical step 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-guideline no.1. In order to pasteurise, often a plate heat exchanger is used. It is known that these exchangers - even when new - will start to leak, but even more likely after time. Regular inspection is key in order to make sure the highly deformed thin plates of the plate heat exchanger do not suffer from stress and crack corrosion.

After pasteurisation, the whole line, including filling machine(s), must be hygienically designed: meaning cleanable to microbial level. Unless the product is pasteurized after filling, then GMP is sufficient. However, even this is 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 produced by microorganisms (in particular of *S.aereus), may still be toxic after sterilization and will form a threat to the health of the consumer.


Rauheitsmessungen von Edelstahloberflächen (EN)

Although Ra values are commonly used to describe surfaces, the limits of this indicator should not be forgotten. Also the notation is important: “Ra ≤ 0.5 μm”, for instance, does not have the same meaning as “Ra max 0.5 μm”. Surface designations such as “2B” according to EN or “No 4 finish” according to ASTM encompass relatively large ranges of surface roughness. Products which have identical designations but come from different batches or different suppliers may have noticeably different roughness characteristics. In architectural applications where surface appearance is of great importance roughness values alone are insufficient to characterise a surface. In this case, it is recommended that samples should be exchanged between the customer and the supplier and made part of purchase orders, to avoid later disagreement. Reprinted from Euro Inox with permission.


Surface roughness is a measure of the texture of a surface. It is quantified by the vertical deviations of a real surface from its ideal form. If these deviations are great, the surface is rough, if they are small, the surface is smooth. Roughness is typically considered to be the high-frequency, short-wavelength component of a measured surface. In practice, it is often necessary to know both the amplitude and frequency to ensure that a surface is fit for purpose [1].

Ra value

The roughness of a surface has most commonly been measured by an instrument in which a stylus travels across the surface, the movement of the stylus is amplified and the signal recorded. The result is generally expressed as Ra or average roughness and is the arithmetic average value of the deviation of the trace above and below the centre line. The value of Ra is normally measured in micrometres. ISO standards use the term CLA (Centre Line Average). Both are interpreted identically [2].

Euro inox
Figure 1. Das Prinzip der Messung der durchschnittlichen Rauheit (Ra) [3]

Although Ra is a useful average, it does not differentiate between peaks and valleys. Very different profiles can have the same Ra value. In technical specifications, the upper limit or maximum value of the parameter is often found during inspection. For requirements specified by the upper limit (e.g. Ra ≤ 0.6 μm) of a parameter, the surface is considered acceptable if not more than 16% of all measured values of the selected parameter (based on an evaluation length) exceed the value specified in the drawings or the technical product documentation. To designate the upper limit of the parameter, the symbol of the parameter is used without the “max” index. For requirements specified by the maximum value (e.g. Ra max. 0.6 μm) of the parameter during inspection, none of the measured values of the parameter, over the entire surface under inspection, should exceed the value specified in the drawings or in the technical product documentation. To designate the maximum permissible value of the parameter, the “max” index has to be added to the symbol of the parameter (for example Ra max). Control of surface roughness can be performed quickly and easily using the simplified procedure for roughness inspection given in Annex A, EN ISO 4288 [5], [6]. Only the upper limit of roughness is usually established – not a lower limit. An exception is cylinder bores where oil is retained in the surface profile and a minimum roughness is required.

to make a surface cleanable to microbial level, EHEDG is recommending an Ra of below 0.8 micrometer, in absence of crevices, scratches etcetera.

Euro inox
Figure 2. Verschiedene Oberflächenprofile mit demselben Ra-Wert [4]

Rz value

An alternative measure of surface roughness is the Rz value. ISO 4287-1:1997 [7] defines Rz as the maximum height of profile. Older documents and surface roughness measuring instruments may still refer to Rz according to the 1984 version of this standard, which indicated the “ten point height of irregularities”. Typographical detail is important: “Rz” refers to the current, “Rz” to the obsolete version of the standard.

Rq value

Another factor for the description of surface roughness, Rq (sometimes also RMS) measures the root-mean-square deviation of a profile. The terms, definitions and parameters for determination of surface roughness are again provided in EN ISO 4287 [7].

Euro inox
Figure 3. Das Prinzip der Messung der quadratischen mittleren Rauheit (Rq) [8]

Table 1. Surface roughness for different stainless steel finishes [9], [10], [11], [12].

Surface finish EN 10088-2 Type of process route Surface roughness as in EN 10088-2 Notes
1D Hot rolled, heat treated, (shot blasted) and pickled. Rough and dull. Ra typically in the 3.50-7.50 μm range
2D Cold rolled, heat treated, pickled. Smooth.
2B Cold rolled, heat treated, pickled, skin passed. Smoother than 2D. Ra typically in the 0.30-0.50 μm range
2G Ground
Grade of grit or surface roughness can be specified. Unidirectional texture, not very reflective.
2R Bright annealed
Cold rolled, bright annealed. Smooth, bright, reflective.
2J Brushed or dull polished
Grade of brush or polishing belt or surface roughness can be specified. Unidirectional texture, not very reflective.
2K Satin polish Transverse Ra < 0.5 μm
2P Bright polished
The finish is achieved by mechanical polishing. The process of surface roughness can be specified. It is a non-directional finish, reflective, with a high degree of image clarity.

It is worth keeping in mind that incorrect surface treatment can result in irreversible damage. As an example, there is no repair procedure for a process tank delivered with a cold-rolled, bright finish (2B finish, ASTM A 480/A 480M) that exceeds a specified maximum Ra value [6].

Surface finish ASTM A 480/480 M Description Notes
3 A linearly textured finish that can be produced by either mechanical polishing or rolling. A skilled operator can generally blend this finish. Average Ra may generally be up to 1 μm*
4 A linearly textured finish that may be produced by either mechanical polishing or rolling. A skilled operator can generally blend this finish. Average Ra may generally be up to 0.6 μm*
5 Architectural finishes. These are a separate category and can be negotiated between buyer and seller, as there are many techniques and finish variations available throughout the world.* Transverse Ra value should not exceed 0.5 μm
6 This finish has a soft, satin appearance, typically produced by Tampico brushing of a No. 4 finish.
8 This is a highly reflective, smooth finish, typically produced by polishing with successively finer grit abrasives, then buffing. Typically, very faint buffing or polishing lines may still be visible on the final product. Blending after assembly may be done by buffing.

*Surface roughness measurements differ with different instruments, laboratories and operators. There may also be overlap on measurements of surface roughness for both No. 3 and No. 4 finishes.

Surface finish in fabrication Average Ra μm
Bead blasted 1.00-6.00
Bored, turned 0.40-6.00
Electropolished 0.10-0.80

It should be noted that the values in the table are for orientation only and that they vary between different producers and typical surface finish. It is suggested that, as concerns surface roughness requirements, a possible Ra acceptance criterion should be explicitly stated, since surface finish as defined by the standards only defines the process route (such as cold rolled, heat treated, pickled, skin passed for 2B) and surface roughness can vary from one producer to another.

Table 2. Comparison of grit size and surface roughness – approximate values [13].

Grit size Rq μm Ra μm
80 2.02 1.80
120 1.47 1.32
150 1.20 1.06
180 0.86 0.76
240 0.43 0.38
320 0.36 0.30
500 0.20 0.18
600 0.15 0.13

SafeFoodFactory, concerning table 2, Grit size and roughness (from ([13]):
according to the latest measurements the modern grinding paper is too good. I.e. grinding to below 0.8 micrometer Ra can sometimes only be achieved with Grit size 240.

Relevant standards

ISO 1302:2002
Geometrical Product Specifications (GPS) – Indication of surface texture in technical product documentation (ISO 1302:2002)

EN ISO 3274:1997.
Geometrical product specifications (GPS) – Surface texture: Profile method – Nominal characteristics of contact (stylus) instruments (ISO 3274:1996).

EN ISO 4287:1998/AC:2008.
Geometrical product specifications (GPS) – Surface texture: Profile method – Terms, definitions and surface texture parameters (ISO 4287:1997/Cor 1:1998/Cor 2:2005).

EN ISO 4288:1997.
Geometrical product specifications (GPS) – Surface texture: Profile method – Rules and procedures for the assessment of surface texture (ISO 4288:1996).

EN ISO 5436-1:2000.
Geometrical Product Specifications (GPS) – Surface texture: Profile method; Measurement standards – Part 1: Material measures (ISO 5436-1:2000).

EN ISO 5436-2:2012.
Geometrical product specifications (GPS) – Surface texture: Profile method; Measurement standards – Part 2: Software measurement standards (ISO 5436-2:2012).

EN ISO 12085:1997/AC:2008.
Geometrical product specification (GPS) – Surface texture: Profile method – Motif parameters (ISO 12085:1996/Cor 1:1998).

EN ISO 12179:2000/AC:2008.
Geometrical Product Specifications (GPS) – Surface texture: Profile method – Calibration of contact (stylus) instruments (ISO 12179:2000/Cor 1:2003).

EN ISO 13565-1:1997.
Geometrical product specifications (GPS) – Surface texture: Profile method; surfaces having stratified functional properties – Part 1: Filtering and general measurement conditions (ISO 13565-1:1996).

EN ISO 13565-2:1997.
Geometrical product specifications (GPS) – Surface texture: Profile method; surfaces having stratified functional properties – Part 2: Height characterization using the linear material ratio curve (ISO 13565-2:1996)

EN ISO 13565-3:2000.
Geometrical Product Specifications (GPS) – Surface texture: Profile method; surfaces having stratified functional properties – Part 3: Height characterization using the material probability curve (ISO 13565-3:1998)

ISO 16610-21:2011.
Geometrical product specifications (GPS) – Filtration – Part 21: Linear profile filters: Gaussian filters


Surface roughness, Wikipedia,

Surface Roughness Finish (Review) and Equations,

Boen, P., Abrasieve voorbereiding van metaal oppervlakken voor verlijming, 3M, company documentation

Rodriguez, V., Sukumaran, J., Ando, M., De Baets, P., Roughness measurement problems in tribological testing, Sustainable Construction and Design 2011

EN ISO 4288:1997 Geometrical product specifications (GPS) – Surface texture: Profile method – Rules and procedures for the assessment of surface texture (ISO 4288:1996)

Frantsen, J. E., Mathiesen, T., Specifying Stainless Steel Surfaces for the Brewery, Dairy and Pharmaceutical Sectors, Nace Corrosion, 2009, Paper 09573

EN ISO 4287:1998 Geometrical product specifications (GPS) – Surface texture: Profile method – Terms, definitions and surface texture parameters (ISO 4287:1997)

Roughness Parameters,

Surface Textures of Stainless Steels, Technical Focus,

ASTM A 480/480M, Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip

EN 10088-2, Stainless steels – Part 2: Technical delivery conditions for sheet/plate and strip of corrosion resisting steel for general purposes


Surface Roughness Measurements, KEPCO,

umschalten editorial
  • Pasteurisieren - sterilisieren
  • Erfrischungsgetränke
  • Getränk
  • Zucker
  • Lagerung, Transport
  • Tank - Silo