WO1986007578A1

WO1986007578A1 - System for aseptic holding of fermentable liquids in flexible containers

Info

Publication number: WO1986007578A1
Application number: PCT/SE1986/000292
Authority: WO
Inventors: Paul Henri Lefebvre; Edouard Colinet; Henri J. L. LEFÈBVRE
Original assignee: Alfa-Laval Food Engineering Ab
Priority date: 1985-06-17
Filing date: 1986-06-17
Publication date: 1986-12-31
Also published as: LU85954A1; AU6120786A; EP0263828A1

Abstract

For aseptic intermediate storage of liquid products, use is made of containers with flexible walls, which are immersed in water or another liquid. The surrounding liquid is kept in basins made of e.g. concrete or plastic. Since the containers, when they are filled with liquid product, are immersed in liquid, the loads acting on the container walls remain low.

Description

SYSTEM FOR ASEPTIC HOLDING OF FERMENTABLE LIQUIDS IN FLEXIBLE CONTAINERS

The present invention relates to a system for aseptic buffer storage of liquid products which may contain fermentable particles and arrangements associated therewith causing the system to function, whereby the containers may be fixed or mobile. The storage containers consist of flexible, soft casings of any common shape whatsoever but preferably of cylindrical shape and terminated by semi-spherical or other sections, immersed in a liquid which may be water wherein may have been dissolved or dispersed salts in order to adjust the density or to impart desirable characteristics to the water.

The entire system is sterilised prior to commissioning and except for unfortunate contingencies this need not be done again during its service life, provided that the products themselves have been perfectly sterilised by means of known processes before they enter the system and that the stored sterilised products are removed without the sterility in the inner one of the containers ceases to be complete.

The use of soft storage containers makes it possible to avoid any transfer of gas during the successive filling and emptying processes. Experts in this field know how difficult and little reliable it is to sterilise considerable amounts of gas. This problem is eliminated.

The immersion of the soft containers in a liquid entails the following advantages:

Reduction of the loads to which the casing is exposed.

Protection against pilfering, intentionally or by accident, by persons or animals.

Easy control of temperature.

Given a suitable shape of the surface on which the storage container is located, an almost constant pressure is ensured, which facilitates removal of the stored liquids. - Achievement of an automatic back-pressure in the sterilising apparatus and cooling of the product to be stored.

Oxidation of the stored products is reduced or suppressed. As regards the said oxidation, the membrane forming the walls of the soft containers is selected in accordance with the requirements of the product within, the duration of storage and also the intervals between the periods during which the container holds significant amounts of liquid inasmuch as in a soft container in which there is very little liquid the surface/volume ratio is very high as a result of which there is a particular danger of oxidation.

Oxidation of the product within the container can be caused only by penetration of oxygen through the membrane and the outer "mattress" of liquid.

If it is important to reduce oxidation, the system which is the subject of the present invention lowers the oxygen concentration in the immersion liquid by application of one or several of the following processes: - Complete or partial elimination of the oxygen content in the immersion liquid by physical, chemical or biological methods.

Protection or covering of the surface of the liquid, thus causing the rate at which gas is dissolved in the immersion liquid to be suppressed or reduced. - Replacement of air at the surface of the liquid by a gas containing little or no oxygen.

The specification of the invention is completed by examples.

They describe only embodiments and do not restrict the general scope of the invention in any way. EXAMPLE 1

Gener_al arrangement

Storage capacity 36OO m - 12 soft containers each with a capacity of 300 nr - diameter 5 - length 21 m - height in filled state (80 )

2 2.95 m - surface area of empty containers on the ground 2226 m . The 2 containers are arranged in two rows, 6 in each row, within a square basin having a side length of 47_*5 m and a height of 3-5 m (7900 m³).

A central culvert situated underneath the basin enables access to the connection apertures of the containers. In one embodiment the soft container is located within a "cell", the axis of which is parallel with the axes of the containers, whereby the inclination of the longitudinal edge of the cell facing the connection apertures is somewhat larger than the inclination of the natural outlet for the liquid within (the latter being only in exceptional cases Hewtonic). The basin is covered with a roof lined with thermal insulation in order to reduce the thermal losses if storage takes place at a temperature different than the temperature of the ambient air (not more than 25°C with tomato purees and concentrates, 15°C, 10°C and 5°C incl. with sensitive fruit juices). The basin is provided with an arrangement for maintaining a constant level if the individual variations in the degree to which the various containers are filled makes this necessary. If required the basin is provided with a cooling system and an agitator system ensuring a constant temperature. EXAMPLE 2

The conditions were identical with those in example 1 but the basin is formed by weirs, the tightness of which is, if necessary, ensured by a plastic membrane. EXAMPLE 3 Inflow of liquid which fills the basin

300 m container.

Diameter 5 m - height to filled state (80$) 3 m-

Density of liquid within the container: 1.2 kg/litre.

Density of outer fluid: 0 (a gas). - Pressure on container membrane:

-_ϊ__ _ 1 -2 * 00² _χ J _{2? on} 2

4 - 4 ^x 1000 ^{" {} ^^{/ cm}

If the density of the outer liquid is 1 kg/litre the pressure on the membrane will be

0.2 x 300² 1 - - , _/ 2 4 ^{" x} Tooδ ^{= 4}-^{5 g}/^cm

If this density is 1.1 the pressure drops to

If the density of the outer liquid approaches the density for the stored aseptic product, the height of the container increases and it must accordingly be restricted mechanically in order to ensure complete immersion. EXAMPLE 4 Penetration of oxygen into the liquid product within the container

The inner liquid affects the rate at which the oxygen penetrates. Under conditions of equilibrium it does not affect the oxygen content of the product within the container, unless the oxygen content in the outer liquid is artificially reduced either directly or indirectly by reducing the oxygen content of the atmosphere above the basin or by a combination of these two measures.

As regards the soft container in accordance with example 1 , with a membrane of high density polyethylene, the oxygen permeability is

3-2 cm /cm/day/atmosphere/m . Let us bear in mind that the permeability of the oxygen in a stationary layer of water may be estimated to amount to

^"*i ^""> 2

10 cm /cm/day/atmosphere/m (stationary layer, not supplied with oxygen from the start).

Permeability of the high density polyethylene membrane having a thickness of 0.2 cm:

3.2 x 0.2 - 3 , _/ 2 -^"—^"2 = 3-2 cm ^day/m

Permeability of a 50 cm layer of water:

^J 1 —0³ -T x_Q 0.2 = 4 , cm 5-y_/d,ay/ _/m 2

The total permeability is as follows!

The influence of the layer of water can be estimated theoretic¬ ally.

It is virtually zero if the water is vented and in motion. On the other hand, any transfer of oxygen to the sterile product can be prevented if the outer liquid, also if it is agitated, does not contain oxygen. With a membrane having reduced permeability, of the type consisting of 2 mm high density polyethylene and 0.01 mm "CLARENE L" (Solvay) the permeability of the barrier product, Clarene, is as follows:

_A ^*"i P 6 10 cm /cm/day/atmosphere/m .

The permeability of the Clarene layer amounts to 6 x 10^"4 x 10⁵ x 0.2 = 0,12 c cLay/m² and the total permeability comes to

? = 3^2 ⁺ 4 ⁺ 0÷]2 = ⁸'⁸9

where P = 0.112 cm /day/m .

The influence of the water and polyethylene layers is negligible. 1 cm oxygen weighs

22400 - ⁷'^{14 10"4 δ}

The surface/volume ratio of the container in question amounts to about 1.1 when it is filled. If the container is empty the layer of water has a thickness of at least 3 m, i.e. it is at least six times as large. With a membrane of pure polyethylene we have:

1 . -1- ₊ . 1.81

The total permeability amounting to P = 0.552 cm /day/m

With a membrane of polyethylene and Clarene we obtain: P 3.2 ⁺ 4 0.12 = 10.1

3 / 2 where P = 0.0986 cm oxygen/day/m .

Since the surface/volume ratio increases to a much greater extent than the improvement resulting from the increase in thickness of the water layer, the container content is oxidised more quickly.

In practice it is in general better to ignore the barrier effect of the water and to make use of a container constructed on the basis of a membrane which as such ensures adequate impermeability to oxygen and to aromatic substances, it being however advantageous to take, in the special cases, various precautions by reducing the content of oxygen in the immersion liquid.

EXAMPLE 5 The soft containers are in the main intended for intermediate storage of costly fruit derivatives which are very sensitive to oxygen and heat, justifying a higher investment than with tomato derivatives.

One constructs several independent basins, insulates them completely, cools the sterilised products prior to storage and applies an oxygen barrier which flows on the cooled water in the basins. Also if this water is degassed, the air above the basins is replaced by a gas having a very low oxygen content, whereby the intended space is gas-tight. As a result the amount of oxygen penetrating into the soft containers in the course of a day is nearly zero. The stability of the stored products is excellent, even if the amount of sterile product in the containers is negligible and one must, on occasion, wait for more than one year before they are refilled.

The necessary and sufficient conditions ensuring industrially excellent stability may be summarised as sterility, low temperature and the absence of oxygen.

Claims

PATENT CLAIMS

A system for aseptic intermediate storage of liquid products, possibly containing particles the dimensions of which may reach 50-100 mm, the said products being sterile but capable of fermentation when their temperature is between 0 and 50°C, and arrangements associated therewith causing the system to function, it being possible for such containers to be stationary or mobile, c h a r a c t e r¬ i s e d by the following features, jointly or severally:

1) In its simplest embodiment use is made of one or several containers which are rigid or at least possess relatively stable shapes and dimensions, each and every one of them containing one or several soft containers sterilised prior to use or sterilised after use, and each and every one equipped in such a way as to enable it to be filled or emptied without restriction in an aseptic manner and without any sterile gas leaking in, owing to at least one pipeline and an aseptic valve which are sterile or sterilised, whereas the soft container which may have any capacity or shape whatsoever but has in general a capacity between 50 and 1000 m and is cylindrical, is immersed into a liquid serving to reduce the mechanical loads acting on the soft walls, to reduce or prevent oxidation of the sterile liquid, to cool it at a later stage or to maintain the temperature constant, to exert a static pressure on the sterile liquid and finally to protect the soft container from pilfering, with intent or by accident, by persons or animals, as well as against other external effects such as solar radiation. 2) The outer containers containing the immersion liquid and the soft containers consist of concrete, masonry, metal, plastic or earth and earthworks possibly made watertight with the aid of a plastic film.

3) The soft containers are made of plastic or elastic films tight in respect of micro-organisms, the permeability of which for water, aromatic substances and oxygen is either low or virtually zero, depending on the requirements.

4) The soft containers and the aseptic pipelines and the valves which are assembled direct can be sterilised with the aid of gamma rays, heat, antiseptics or a combination of these means, whereby the heat originates from outside or inside and in the latter case is provided by means of a liquid, steam or a mixture consisting of a non-condensable gas, a warm water vapour or an entirely different liquid and a chemical product which rapidly destroys the micro¬ organisms.

5) The aseptic pipelines and/or the valves in the soft containers are linked with the latter at any point whatsoever, at the bottom, on the sides or at the top, whereby the pipelines, if any, are rigid or capable of being deformed.

6) The soft container is provided with one or several aseptic pipelines and/or valves for external connection with a view to enabling sterilisation, flushing, filling and emptying of the container, whereby the normal operations are limited to a sequence of aseptic filling and emptying operations separated by intervals during which the soft container serves for aseptic storage of liquid sterile products, whereby the temperature of the latter as well as the amounts of oxygen which they absorb is adjusted in such a way as to maintain, for the required time, the quality at the required level. 7) Couplings between the soft containers and the network of connection lines upstream and downstream are so designed as to ensure that the temperatures required for thermal sterilisation of the said networks of lines do not destroy the soft containers, owing to the selection of material which conducts heat badly or owing to a local cooling arrangement for the pipelines connected to the soft container.

8) The immersion liquid is cooled or heated in order to cool the content of the soft container or to prevent it from solidifying.

9) The immersion liquid is isolated from the outer air owing to a barrier with very low gas permeability, which floats on the surface of the liquid or is retained between the said surface of the soft container.

10) The basin surface is protected by an enclosure, the walls of which may be insulated and access to which under normal operating conditions can be made impossible. 11) The air in the enclosure which is situated above the basin is replaced by a gas containing little or no oxygen.

12) The walls of the soft containers facing the drainage apertures of the latter are reinforced and provided with outer clamping screws or cables which restrict their movement, prevent them from blocking the openings, interrupt if necessary the extraction and follow an indicator for the filling level.

13) The walls of the soft containers follow an indicator for the filling levels and a safety arrangement whichstops the filling process before it subjects the membrane to excessive pressure.

14) The immersion liquid is water or a mixture of water and dissolved or suspended salts which increase the density and/or absorb oxygen and/or increase the viscosity.

15) The oxygen content in the immersion liquid is lowered by physical means such as degassing under vacuum or cooling under vacuum.

16) The oxygen content in the immersion liquid is lowered by physical means such as intimate contact with a neutral gas.

17) The oxygen content in the immersion liquid is lowered by chemical means.

18) The oxygen content in the immersion liquid is lowered by biological means with the aid of micro-organisms or enzymes and an oxygen receiver.

19) The immersion liquid, the oxygen content of which is reduced or zero, circulates within the basins from below upward, the said basins being provided with an overflow which prevents any reoxygenation of the fluid if the latter is circulated.

20) The soft container is free within the immersion liquid.

21) The soft container is retained laterally within the immersion liquid.

22) If the density of the immersion liquid is higher than that of the sterile liquid within the soft container the latter is kept in the immersed state by means of a net. 23) The walls of the rigid container which are in contact with the walls of the soft container are provided with an arrangement for conditioning the suitable temperature by circulation of the immersion liquid or direct by heat transmission.