Method and a system for converting liquid products into free-flowing powders with pre-cooling

Abstract

The present invention relates to a method and a system for converting liquid products for the cheese making or casein producing industry into substantially free-flowing powdery products, by subjecting the liquid product to heating to a temperature above the crystallisation temperature of any component in the liquid product in a heat exchanger, flash separating volatile components from said heated liquid product to obtain a past concentrate, pre-cooling a fraction of said past concentrate, and drying said combination product. By the pre-cooling it is possible to create lactose crystals by an extremely rapid in-line pre-cooling without any significant increase in viscosity (which would lead to an un-pumpable paste). It is assumed that only a fraction of the paste gets into contact with the walls of the cooler causing a rapid formation of a high number of seed crystals. Further, it is assumed that the seed promote the formation of lactose crystals during the subsequent drying process.

Description

[0001] The present invention relates to a method and a system for converting liquid products from the cheese making or casein producing industry into substantially free-flowing powdery products.[0002] 1. Background of the Invention[0003] The traditional cheese making and casein manufacturing industry produce a series of liquid products and by-products, in the present context termed whey: acid whey, sweet whey, salt whey, permeates from the production of whey protein or milk protein concentrates. Other liquid products are lactose solution, mother liquor from lactose crystallisation, demineralised whey and the like.[0004] Depending on origin the whey contains 5.5-6.5% total solids, wherein 0.7-0.9% protein, 0.05% fat, 4.24.6% lactose and 0.5-0.8% ash.[0005] Usually, after a number of pre-treatments, the aqueous whey is a solution in which the lactose is in an equilibrium of 60% beta- and 40% alpha molecular form. This mixture is very hygroscopic and unsuitable for drying for creating ...

AI Technical Summary

Benefits of technology

[0025] When concentrating liquid products as defined above, it is of importance to control crystallisation, especially of lactose. Lactose crystals inevitably form deposits on heat exchanger surfaces and prevent heat transfer. Therefore, the temperature of the liquid must be maintained above the temperature at which crystals form during the evaporation process. In particular, no formation of .alpha.-lactose crystals occurs when the liquid product is heated to the temperature above crystallisation temperature. High temperatures on the other hand promote the undesired browning (Maillard) reaction and denaturation of proteins (Reyes, F. G. G. (1982) J. Food Sci., 47, 1376-7). The extent of these undesired reactions is minimised by a short residence time at elevated temperatures in the heater. Therefore, a heat exchanger, with a short contact time, is preferred. By the term heat exchanger is meant any suitable heater providing a fast and even heating. Thus a heat exchanger may be any conventional heat exchanger, such as a plate heat exchanger, a "scraped-surface heat exchanger" and a tube heat exchanger. A plate heat exchanger is preferred, such as a heat exchanger having a high ratio of height to width, such as a ratio from 2.5 to 3.5.

[0026] The heat exchanger may also be an electroheating means providing volumetric heating by means of direct electrical resistance heating, also called ohmic heating. Thus, the liquid whey product is preferably heated to at least 80.degree. C. in a heat exchanger. By heating to at least 80.degree. C., more preferred to at least 85.degree. C., even more preferred to at least 90.degree. C., the risk of crystallisation in the heat exchanger is significantly reduced.

Problems solved by technology

It has been found, however, that the crystallisation process makes the whey paste from the evaporator highly viscous and difficult to handle and disintegrate in the Spin Flash dryer when conducted in large scale production.

The process requires relatively heavy duty mixing and feeding equipment.

Therefore, there is an unfulfilled demand for a process for converting liquid products, such as whey, into a substantially free-flowing powdery product, and which process makes less demand on mixing equipment.

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