Process steam in the food industry - requirements, steam qualities and standards

Why steam is indispensable in food production

Process steam is one of the most important and at the same time most invisible utilities of the modern food industry. Whether for cooking, blanching and pasteurising, for sterilising tinned goods, for steam injection in the baking oven or for CIP cleaning of plants — without precisely controlled steam, food can be produced neither safely nor economically.

Steam, however, is not simply steam. What matters is whether the steam only transfers heat indirectly or comes into direct contact with the food. Highly different requirements for purity, choice of materials and conformity with standards follow from this distinction. This article gives an overview of the steam qualities, the typical applications, the relevant hygiene requirements and standards, and of the question why electric steam generation is particularly well suited to food businesses.

Steam qualities: utility steam, clean steam and pure steam

In the food industry, three steam qualities are distinguished according to contact with the product. Choosing the right one is the basis for food safety and cost-effectiveness alike.

Utility steam (Betriebsdampf)

Utility steam is used for indirect heating and doesnotcome into contact with the food — for example in heat exchangers, double-walled cooking kettles or heating coils. The purity requirements are moderate; availability, pressure stability and energy efficiency are to the fore. Typical uses: heating of cooking kettles, indirect sterilisation, space heating in production.

Clean steam (Reindampf / culinary steam)

Clean steam comes into direct contact with the food or with product-contact surfaces. It must be free of chemicals, corrosion products and microbiological contamination. Typical applications: steam injection in baking ovens, direct steam injection into the product, CIP cleaning (Cleaning in Place) and the sterilisation of filling and packaging lines.

Pure steam (Reinstdampf)

Pure steam is the highest purity level and is produced from treated, low-salt water in special pure steam generators. It is used above all at the interface with pharmaceutical and sensitive food production, for example when sterilising plant components that come into contact with sensitive products. Here the strictest requirements apply to non-condensable gases, dryness and superheat.

Applications of process steam in the food industry

The range of steam applications reflects the diversity of food production.

Cooking, blanching and steaming

Steam transfers heat gently and evenly. When blanching vegetables, enzymes are inactivated and colour as well as nutrients are retained; when steaming, the product stays juicy. Precise temperature control determines the product quality.

Pasteurising and sterilising

In pasteurisation (e.g. milk at 72 °C for 15 seconds) and in the sterilisation of tinned goods, steam ensures the reliable reduction of micro-organisms. Reproducible temperature/time profiles are safety-relevant here.

Steam injection in the baking process

In deck and rack ovens, injected steam creates the glossy, crisp crust of bread and rolls. The steam volume has to be quickly available and precisely metered.

CIP cleaning and sterilisation of plants

Cleaning in Place cleans and disinfects pipework, tanks and filling lines without dismantling. Steam is used for thermal disinfection and for the sterilisation of product-contact surfaces.

Packaging

Steam also plays a role in the packaging line — for example when shrinking labels onto shrink sleeve machines, where food-compliant steam of precise quality is required. We cover this application in depth in the article on steam generators for sleever machines .

Hygiene and purity requirements

As soon as steam comes into direct contact with food or with product-contact surfaces, it becomes part of the product — and is subject to the same hygiene requirements. Three levers are decisive:

• Materials:product-contact parts made of stainless steel, usually 1.4404 / AISI 316L, corrosion-resistant and easy to clean.
• Surface finish:low surface roughness (guide value Ra ≤ 0.8 µm) prevents deposits and biofilm formation.
• Design:low-dead-space, self-draining design in line with hygienic design principles, so that no residues or germs can collect.

Added to this are freedom from additives such as film-forming amines, which occur in conventional boiler feedwater treatment, and the control of non-condensable gases, which can impair the sterilisation effect.

Standards and regulations

Several sets of rules define when steam is regarded as safe in the food industry.

DIN EN 285 — steam for sterilisation

Defines limit values for sterilisation steam, among them non-condensable gases (max. 3.5 % V/V), dryness value (min. 0.95) and superheat (max. 25 °C above saturation temperature).

EHEDG — Hygienic Engineering & Design

The European Hygienic Engineering & Design Group publishes guidelines on the hygienic design of plants and steam systems: materials, surfaces, avoidance of dead space and cleanability.

HACCP and VO (EG) Nr. 852/2004

The European food hygiene regulation obliges businesses to operate HACCP-based self-monitoring concepts. Steam that comes into contact with food is to be included in the hazard analysis as a utility.

FDA 21 CFR (export to the USA)

Relevant for export to the USA: steam that comes into contact with food must be free of substances hazardous to health; permitted additives are listed there.

Energy efficiency and electrification of steam generation

The decarbonisation of industry does not stop at steam generation. Electric steam generators offer food businesses a double advantage here — hygiene and carbon footprint at the same time.

• No combustion products:Without a burner, no flue gases and no combustion residues arise that could get into the steam. The steam is inherently cleaner — a direct hygiene advantage.
• High efficiency at the point of use:Electric steam generators can be installed decentrally, close to the consumer, without a chimney and without a gas connection. This minimises pipework and standstill losses.
• Precise control:Electric heating elements control temperature and pressure exactly — important in sensitive processes such as milk pasteurisation or chocolate tempering.
• CO₂ footprint:Operated with green electricity, electric steam generation is emission-free in operation. We cover the detailed comparison of efficiency, emissions and operating costs in the efficiency article .

For steam generation in food production, DINO offers compact electric stainless steel steam generators with steam outputs from 4 kg/h to over 384 kg/h. The units are ready for operation within a few minutes and are ideal for decentralised installation close to the consumer. To the steam generator product overview

Selecting the right steam generator

For direct product contact, a stainless steel design and suitable water treatment are mandatory; for indirect heating, cost-effectiveness and rapid availability are to the fore.

A typical example from packaging: for labelling on shrink sleeve machines, food-compliant steam of precisely controlled quality is decisive — you can read how a steam generator is designed for this in the in-depth article “Steam generators for sleever machines: food-compliant steam” .

DINO accompanies food businesses from needs analysis through design to commissioning — manufacturer-neutral in the steam quality, but uncompromising in hygiene and reliability.