SPX FLOW can provide complete systems and process line upgrades for the manufacture of high quality low-fat spreads. SPX FLOW has wide ranging experience in:
- Process know-how
- Project management
- Ingredients reception & storage
- Recipe preparation & blending
- Fermentation systems
- Membrane concentration
- Re-work systems
- In-place cleaning
- Process automation
Storage and blending of oil phase
Most oils are received in liquid form and stored at a controlled temperature, to avoid crystallisation. This may be achieved either by using special insulated, heated vessels, or more commonly, by locating the vessels in temperature controlled rooms.
Installation of pipework and pumps for the transfer of oils must be carefully considered. Any equipment located outside temperature controlled rooms may need to be heated and insulated. SPX FLOW offers suitable equipment to cover all of these requirements.
The first process stage for low-fat spreads is to blend together suitable fats or oils to give the desired functional properties including spreadability, melting point, texture and flavour. In general, a relatively high melting point hydrogenated fat is mixed with a softer fat.
It is usual to blend in any oil soluble minor ingredients, such as vitamins and lecithin, at this initial blending stage. Accurate addition of recipe quantities and good dispersion are very important. Two basic process options may be considered for blending:
a) Batch mixing
Typically two vessels are provided so that one may be used for the blending operation whilst the second feeds blended oil to subsequent process stages on an alternate basis. These stainless steel vessels have a special agitator to give rapid and effective blending and are built to meet the most demanding hygiene standards.
b) Batch/continuous systems
For larger scale and more automated production, it is common only to batch mix the minor ingredients in a small quantity of the base oil, using a special APV agitator. In this case, it is usual to provide only a single blending vessel from which the prepared mix is pumped to a buffer vessel, which provides a continuously metered feed. Simultaneously, the main proportions of oils are metered directly to the final blending/emulsification stage, where they meet other ingredient streams.
Processing of aqueous phase
In many recipes, the aqueous phase is based on dairy products. Ripened skimmed milk was originally used in margarine to give a mild, buttery aroma, but in many modern margarines and spreads whey, in the form of powder or concentrate, is now substituted and boosted with added flavourings. Ripened skimmed milk is used particularly in low-fat spreads where it is very effective in thickening/gelling and emulsification of the product.
Two alternative aqueous phase preparation techniques may be followed:
a) Preparation of ripened milk
Concentrated (typically 15-18% total solids), chilled, skimmed milk is stored in insulated vessels at approximately 5°C. However, if the milk arrives at temperatures higher than 7°C, an APV Paraflow plate heat exchanger should be used to pre-cool the incoming product using chilled water or glycol. Alternatively, an APV reconstitution system may be used to prepare a suitable feedstock from skimmed milk powder and water or from skimmed milk fortified with milk powder.
After storage, the milk is pasteurised using an APV Paraflow heat exchanger, typically at 90°C with 60 seconds hold. Pasteurised milk is cooled regeneratively and passes to vertical, insulated and agitated culture vessels equipped with two-speed agitation. High speed is used to ensure good dispersion without air entrainment during culture addition, whilst low speed is used to gently break the curd at the end of incubation.
The pasteurised milk is inoculated with starter culture and incubated. Ripening is allowed to continue until a pH of 4.3 is reached, when the maximum amount of flavouring substance is developed. The culture is then cooled to 5°C to stop fermentation. Total ripening time is dependent on the starter culture used as well as fermentation temperature. The proportion of ripened milk to fat blend is calculated to give a finished spread with the required amount of water.
For low-fat spreads, APV's membrane filtration processes can be used to concentrate the cultured milk without thermal denaturation for improved quality.
b) Preparation of the aqueous phase without ripened milk
When the aqueous phase is not based on cultured skimmed milk, it may include any of the following dairy ingredients:
- Whey as concentrate or powder
- Skimmed milk concentrate or powder
- Casein or caseinates
- Salt or chilled brine
- Protein or carbohydrate based fat replacers
- Emulsifying salts
- Carragheenen or other stabilisers
These must be thoroughly despersed before emulsification. This is usually carried out using an APV vertical cylindrical vessel equipped with a high speed agitator.
Blending and emulsification
Whichever recipe is selected, it is now necessary to blend together the aqueous and oil phases to produce a pre-emulsion which will remain stable until it reaches the cooler/crystalliser. Either a batch or continuous system may be used depending upon the level of automation and scale of production.
a) Batch blending
Ingredients are pumped to one of a pair of blending/emulsifying vessels operating on a "flip-flop" basis, feeding to the pasteurising plant. These vessels are usually load cell mounted to facilitate metering and suitable agitation is provided to ensure that the mix is thoroughly blended to prevent separation prior to crystallisation. It is important to control the shear level carefully since excessive agitation can lead to phase reversal. For smaller batch sizes, SPX FLOW offers vertical stainless steel vessels equipped with a single high speed agitator. For very large batches, dual agitation may be necessary.
b) Continuous blending
For larger systems, SPX FLOW offers continuous metering and blending combined with in-line high-shear mixing to give the formation of the pre-emulsion. This type of system is very effective in achieving consistent and controlled pre-emulsification on a larger scale.
For very low-fat products containing fat replacers, very high pressure homogenisation may be used immediately after blending. This helps in the formation of a stable emulsion and, by using pressures of 500 to 1,000 bar, produces very small particles of fat replacer gels to simulate the mouth feel of fats. An APV Hyper Homogeniser has been specifically developed for this task.
Pasteurization and re-work melting
Most manufacurers pasteurise the complete recipe prior to crystallisation. SPX FLOW has developed a specialprocess which allows simultaneous pasteurisation and melting of re-work (normally a minimum of 5%, but depending on the characteristics of the downstream filler it can be designed to accommodate up to 100% re-work). This overcomes the need for separate batch melting systems in which oxidative product deterioration can occur. Moreover, the duplication of pasteurising and re-work melting in the same equipment reduces the overall plant cost.
Pasteurised product is cooled by regeneration followed by recirculated attemporated water to the required temperature for entry to the cooler/crystalliser.
When the product includes significant salt content, the plates of the APV Paraflow are constructed of titanium. If only unsalted products are manufactured, stainless steel plates may be used.
Chilling and crystallizing
The pasteurised mix now passes to the cooler/crystalliser. For harder products, the product is fed using a triplex piston pump whereas a rotary pump is adequate for most low-fat spreads.
In all cases, cooling takes place using specialised scraped-surface heat exchangers with direct expansion of refrigerant in the jacket.
This is usually carried out in multiple scraped-surface barrels, often with inter-stage texturising/emulsification using pinworker units. Special high-speed pinworkers may be required for some types of low-fat spread. For harder products, resting tubes fitted with a series of perforated plates may be provided just prior to filling or depositing.
Filling and packaging
Following cooling and crystallisation, it is necessary to either package or deposit the product under controlled hygienic conditions. APV Systems is able to provide such facilities using its own equipment, or alternatively, can offer advice on the selection of machinery available from complementary filling equipment manufacturers.
All items of unit equipment are especially designed to enable effective cleaning in place and can be linked into a total cleaning system. APV packaged in-place cleaning units provide recovery systems which minimise the use of chemicals and water and reduce effluent. Recentlyour systems have become even more environmentally friendly and cost effective by including membrane filtration of the cleaning fluids for selected applications. All APV equipment and processes meet stringent world hygiene standards and ensuer that cleaning is both efficient and reliable, requiring only a minimum of manual intervention.
Varying levels of automation are available to meet the specific needs of the end user. Where the requirements is for a basic manually operated installation, only the critical temperature and pressure parameters are automatically controlled. Alternatively, state-of-the-art microprocessor-based control systems with direct links to APV management information systems are available.