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Innovations in Stork tubular flow concept.

Innovation in Stork Tubular Flow Concept

The tubular flow concept for the UHT treatment of milk has been employed successfully for many years. Of a recent date is the application for longlife UHT milk with a high level of turbidity (NTU 50). Stork has analyzed the process parameters to be satisfied for the manufacture of grade AA milk on an indirect heating system.

Under the direction of Mr. J. Mottar, the Belgian Government Dairy Research Station at Melle has established a standard for AA milk, a premium quality UHT milk. The Belgian processors are interested in the processing of AA milk, because they are allowed to ask a higher price for this type of milk; farmers also benefit from the extra price.

The dairy research station insists that AA milk must satisfy a minimum requirement of 50 NTU. NTU stands for Neophalic Thermal Unit, a unit used to measure the intensity of the heat treatment to which the UHT milk has been subjected during manufacture because such treatment affects the turbidity.

Until recently, only direct heading systems were able to manufacture UHT milk conforming to these standards. Such systems operate on the principle of injecting steam into the product in order to bring it to the appropriate sterilization temperature; this stage is followed by flash cooling.

In terms of energy consumption, the direct heating system is considerably less favourable than the indirect tubular flow system. A direct heating system is characterized by high steam consumption, say 140 kg of steam per 1000 litres of milk. In contrast, steam consumption with indirect heating systems is as low as 30 kg of steam per 1000 litres of milk.

In addition, the cooling water consumption in direct heating systems is high, owing to their comparatively poor thermal regeneration efficiency. The maximum regenerative heating temperature in direct heating systems is only about 70 [degrees] C. Heating from 70 [degrees] C to 140 [degrees] - 145 [degrees] C is effected in a matter of seconds by steam injection. The subsequent flash cooling from 140 [degrees] - 145 [degrees] C to 70 [degrees] C involves some 2500 litres of cooling water per 1000 litres of milk. Indirect systems have a much better thermal efficiency, and increasing energy prices undoubtedly constitute an effective incentive for processors to employ the Stork indirect heating system for UHT treatment.

Stork has analyzed how its indirect UHT systems could be rendered suitable for the manufacture of AA milk. The research conducted was specifically related to the Stork Sterideal UHT plants having outputs of 13,000 and 20,000 litres per hour, feeding two or three aseptic fillers with a capacity of some 6000 litres per hour each. After a number of exploratory tests in the Stork R & D Centre at Nieuw Vennep, a prototype was built to serve as a model for the systems referred to above.

For a period of nearly a year, various UHT sterilization tests were performed on the prototype, which served to evolve the final concept. UHT product samples were frequently analy for their NTU values by the Belgian Government Dairy Research Station at Melle. Finally, Stork defined the process parameters to be satisfied by the high capacity UHT systems for the manufacture of AA milk.

During the spring of this year, a Stork Sterideal UHT plant, with an output of 20,000 litres per hour and capable of manufacturing AA milk, went on stream in the Dison-based creamery of Interlac.

Stork Sterideal plants in great demand

In this context, it should also be noted that several years ago, Interlac also commissioned the first Stork Sterideal UHT plant with a rated capacity of 20,000 litres per hour.

The Sterideal types for outputs of 13,000 and 20,000 litres per hour, introduced by Stork a few years ago, have turned out to be a tremendous success. They allow optimum heat treatment and, in common with the basic concept, ensure unimpaired product integrity, even at considerably reduced outputs. To this end, the effective heat transfer surface areas of the main heater and regenerator incorporated in the system are automatically adapted to the relevant plant output and, in addition, the main heater inlet temperature is controlled by a cooling water control system.

High capacity Sterideal plants are also successfully employed by processors in many European countries. In countries outside Europe, Stork Sterideal UHT systems are operated to good purpose for a wide variety of products, including soya milk, Milo, Ovaltine, chrysanthemum tea, herbal tea and ice tea, as well as fruit juices, flavoured milk drinks, dietary products and evaporated milk.

Stork SteriJuice: a successful concept

The SteriJuice plant for aseptic processing of fruit juices is based on the unrivalled tubular heat exchanger concept used for the Sterideal. The power of this concept lies in the fact that the product flows through a single, uninterrupted product channel. Unlike the Sterideal plant, the SteriJuice does not include a homogenizer; instead, it employs a positive displacement pump which forces product through the tubular heat exchanger system at a high velocity. Process conditions differ somewhat from those of the Sterideal: the processing temperatures for high acid fruit juices are usually lower (around 95 [degrees] C) and, in addition, the process control settings are adjusted to suit the viscosity and thermal conductivity of the fruit juice to be processed.

During the course of this year, Frumat of Morocco will commission its second SteriJuice plant for the aseptic processing of orange juice. Frumat will specifically employ the 20,000 litres per hour plant for bulk production of longlife premium quality concentrate. This unit is being hooked up to a bag-in-bag packaging system.

Several other SteriJuice plants, configured to suit the aseptic processing of fruit juices containing a high percentage of pulp, were also successfully commissioned recently by processors in other countries.

Liquids containing particulates larger than 1 cm in size are processed on a Stork system named Steripart.

Steripart pilot plant for Single-Flow FSTP available for customer-oriented trial runs.

Single-Flow Fraction-Specific Thermal Processing of pumpable food products containing particulates can be successfully effected on the Steripart. The plant's heat exchanger system processes the liquid and particulate fractions in a single pass, it being understood that the individual fractions are subject to their own specific heat treatments. In one or more selective holding sections, each size fraction is retained for adjustable periods of time.

In mid-1989, the Steripart pilot plant was commissioned at the Stork R & D facility at Nieuw Vennep. This plant is available for the performance of commercial trial runs and the development of product formulations in close cooperation with food processors.

The Steripart pilot plant is capable of handling pourable products containing particulates as large as 15-18 mm. Typical food products include clear and cream soups containing particulates such as vegetables, vermicelli and meat chunks, yogurt drinks and desserts with identifiable fruit particles, as well as meat sauces and ragouts.

The aseptic filling unit hooked up to the Steripart system allows the filling of heat-treated product in glass jars.

Time and again the Stork tubular heat exchanger concept proves its superior operating efficiency and capability in handling a wide range of diversified products without affecting their product integrity. No wonder that the food processing industry is showing a major trend towards the application of the tubular heat exchanger concept for the UHT processing of food products.

Stork has a great lead in this field, thanks to its know-how and unique tube-coiling method, and it is committed to maintain this lead by a policy of constant development and innovation.

PHOTO : Stork's latest commercial pilot plant - the Steripart
COPYRIGHT 1990 Food Trade Press Ltd.
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Copyright 1990 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Stork Brabant B.V.
Publication:Food Trade Review
Date:Oct 1, 1990
Previous Article:Preservation and Storage of Grains, Seeds and their Related By-Products.
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