WO1990006341A1

WO1990006341A1 - Improvements in or relating to polysaccharide systems

Info

Publication number: WO1990006341A1
Application number: PCT/GB1989/001476
Authority: WO
Inventors: John Richard Mitchell; John Brent Reed
Original assignee: University Of Nottingham
Priority date: 1988-12-09
Filing date: 1989-12-11
Publication date: 1990-06-14
Also published as: AU4745590A; GB8828795D0

Abstract

A performance enhancing additive for neutral polysaccharides and particularly those containing beta 1-4 linked mannose units. The additive comprises an anti-oxidant in the form of a gallate, preferably propyl gallate, and an oxygen scavenger in the form of sodium sulphite or metabisulphite.

Description

Improvements in or relating to Polysaccharide Systems

This invention ^' relates to enhancing the performance of polysaccharides and especially stabilizing thereof, particularly neutral polysaccharides, and more particularly polysaccharides containing beta 1-4 linked mannose units-

Examples of such polysaccharides are the galacto annams e.g. guar gum, locust bean gum and tara gum, and glucomannans.

The addition of performance enhancing additives to polysaccharide systems can provide a stabilizing effect thus substantially reducing degradation on heating and irradiation. As a result viscosity is maintained and where the polysaccharide is used as part of a gelled system gel strengths are maintained after heating or irradiation and syneresis is reduced. Further the performance enhancing additives can increase the rate of viscosity development following polysaccharide addition.

According to the present invention there is provided a performance enhancing additive for polysaccharides comprising a component which is one or more of an anti-oxidant, a free radical scavenger or a free radical terminator . Preferably the additive comprises an oxygen scavenger. Alternatively the dissolved oxygen in a polysaccharide system may be removed by other means, for example by purging with nitrogen or helium, by heating, i.e. boiling, or by applying a vacuum.

The component preferably comprises a gallate, either propyi gallate or octyl gallate. Alternatively the additive may comprise thiourea.

The oxygen scavenger is preferably a sulphite and desirably sodium sulphite. Alternatively a etabisulphite such as sodium metabisulphite may be used.

The proportion of the component is preferably equal to or less than that of the oxygen scavenger. The proportion—nA-the component to oxygen scavenger is preferably in the range 1:1 to 1:10 and desirably substantially 1:3.

Also according to the present invention there is provided a method of enhancing the performance of a polysaccharide system comprising adding an additive according to any of the preceding five paragraphs to the system. As an alternative or in addition to providing an oxygen scavenger in the additive the dissolved oxygen in the system may be removed by purging with a gas such as nitrogen or helium, by heating or by applying a vacuum.

Preferably the polysaccharide system comprises a neutral polysaccharide, and desirably this polysaccharide, contains beta 1-4 linked mannose units.

The pH of the system is preferably maintained in the range 3-12 and desirably 5-10.

Preferably the concentrations of the constituents of the stabilizer in the system are within the range 1-10,000 ppm and desirably in the range 20-1,000 ppm.

Further according to the present invention there is provided a method of enhancing the performance of a mixed gel system comprising a polysaccharide containing beta 1-4 linked mannose units and a further polysaccharide, the method being according to any of the preceding four paragraphs .

The further polysaccharide may comprise one of either carrageenan, agar or xanthan gum. Still further according to the present invention there is provided a dry powder mix of a polysaccharide and an additive according to any of said five preceding paragraphs.

Preferably the polysaccharide contains beta 1-4 linked mannose units.

Experimental examples of use of additives according to the present invention will now be described by way of example only with reference to the accompanying drawings in which Figs. 1 - 8 show tables of results of different experiments illustrating different features of the invention.

Example 1

Solutions of 0.2?ό polysaccharide were prepared in Sorensons buffer also containing 100 ppm sodium azide at pH7. The polysaccharides were dispersed in the buffer and the temperature raised to boiling with stirring. The solution thus formed was divided into two portions. The first portion was cooled to 20°C and the viscosity measured using a U-tube visco eter. The other solution was retorted in a can for one hour at 116°C. The retorted solution was cooled and the viscosity measured using a U-tube viscometer. Viscosities were measured relative to a buffer solution not containing polysaccharide.

The table in Fig. 1 shows the viscosity obtained for solutions prepared by the above method of four polysaccharides with and without retorting and with and without addition of an additive according to the invention. The additive in this example comprised sodium sulphite and propyi gallate forming concentrations in the solution of 800 ppm and 500 ppm respectively. In Fig. 1 the five polysaccharides are as follows:

1 ) Guar gum

2) Locust bean gum

3) Xanthan gum

4) Tara gum

These conditions are as follows:

A. No retort and no additive

B. Retort but no additive

C. No retort but additive

D. Retort and additive

The table shows that the additive is significantly more effective with the neutral polysaccharides guar gum, locust bean gum and tara gum, than the anionic polysaccharide xanthan gum.

Example 2

Fig. 2 shows the effect of varying the concentrations of sodium sulphite and propyi gallate relative to each other in a solution of guar gum prepared as described in example 1. In this figure, E is the concentration in of sodium sulphite (ppm), F the concentration of propyi gallate (ppm), G the viscosity without retort and H the viscosity with retort, relative viscosities were measured as in example 1.

This' shows that the additives are effective at suprisingly low concentrations e.g. total additive concentration of 40 ppm prevents viscosity less on boiling and 130 ppm prevented viscosity less on retorting.

Example 3

Solutions of 0.8?ό guar gum were prepared in Sorenson's buffer pH 7.0 by mixing the buffer, at room temperature, with a Silverson Homogenizer and adding the dry powder. Sterilizer was added at the same time as the powder to give a final concentration of 200 ppm but using different ratios of sodium sulphite and propyi gallate. The resulting solutions were sealed in cans and retorted at 121°C for one hour. On cooling to 20°C the viscosity of the solutions was determined using a Deer Rheometer fitted with a 4° cone. The results were converted to give the viscosity at a shear rate of 100s

Figure 3 shows the results obtained in which I is the concentration of sodium sulphite (ppm), J is the concentration of propyi gallate (ppm) and K is the viscosity measured in Pascal seconds. The results illustrate the highest iscosity was obtained when the sodium sulphite to propyi gallate ratio was in the order of 3:1. Further the table illustrates that whilst the sulphite on its own has some stabilizing, the most effective results are obtained with mixtures of sulphite and gallate.

Example 4

Samples were prepared and retorted as in Example 3. Viscosity estimations .were carried out using a Brookfield Viscometer (model LVT-spindle 1). One series of samples were dissolved in Sδrenson's buffer, adjusted to pH 7.0, with a second series of guar samples being dissolved in distilled water. For each series a sample was prepared containing 400 ppm sulphite, 250 ppm propyi gallate, 400 ppm sulphite plus 250 ppm propyi gallate, and finally no additives .

Figure 4 is a table showing the results obtained in which a and b are respectively the first and second series of samples with no additive, c and d are the first and second series with only sulphite added, e and f are first and second series with only propyi gallate added, and g and h are first and second series with both sulphite and propyi gallate added. L shows the speed of the viscometer (r.p.m.), M shows the viscosity (cp) and N shows the final pH. This example shows that phosphate, present in the buffer, is not necessary.

Example 5

Guar samples were prepared, half of the samples with an additive including 100 ppm sodium sulphite and 100 ppm propyi gallate, and the viscosity estimated as in example 3. The ratios of the potassium and sodium buffers were varied to give a range of pH values.

Figure 5 shows the results obtained with the pH denoted by 0, the viscosity (cp) measured with a Brookfield viscometer after retorting without additive denoted by P, and with additive denoted by Q. This illustrates that the additives are effective in maintaining viscosity over a wide pH range and benefits are obtained with a pH between 3.0 and 12.0 and the additives are most effective in the range pH 5-10.

Example 6

Guar samples were prepared in Sorenson's pH 7.0 and the viscosity estimated as in example 4. A number of different additives were used as is illustrated in Fig. 6. The additives were as follows:

a) No additive b) Propyi gallate (250 ppm) and sodium sulphite (400 ppm) c) Lauryl gallate (250 ppm) and sodium sulphite (400 ppm) d) Octyl gallate (250 ppm) and sodium sulphite (400 ppm) e) Thiourea (200 ppm) and sodium sulphite (400 ppm) f) Thiourea (650 ppm) and sodium sulphite (400 ppm) g) Thiourea (1000 ppm) and sodium sulphite (400 ppm) h) Propyi gallate (250 ppm) and sodium metabisulphite

(400 ppm)

This example illustrates that beneficial effects can be obtained with gallates other than propyi, though propyi produced the most marked effect. The example also showed that marked effects were produced with thiourea in similar ranges of concentrations. It was also illustrated that sodium metabisulphite could be used in place of sodium sulphite.

Example 7

Gums were added to Sorenson's buffer (pH 7.0, 80°C), with and without additives, and mixed using a Silverson Homogenizer to form a solution of 0.4.0 locust bean gum and either 0.25?ό carrageenan or 0.25?ό xanthan gum. The solution was sealed into cans and some were retorted at 115°C for one hour. The gels were left for at least 12 hours before opening the cans and estimating gel hardness using the Stevens-LFRA texture analyser. The speed used was 2.0mm/sec and the highest reading was noted as the probe traversed 0.5mm into the gel. The additives used were either A 400 ppm sodium sulphite and 250 ppm propyi gallate or B 400 ppm sodium sulphite and 250 ppm thiourea.

The results obtained are illustrated in Figure 7 in which a-c illustrate the results with carrageenan for respectively no additive, additive A and additive B and d-f illustrate the results for the xanthan gum sample with respectively no additive, additive A or additive B. T and U respectively show the breakstrength (g) without and with retort. This example illustrates that the additives are effective in stabilizing mixed gel systems. Result d illustrates that without additive the xanthan gum mixed gel system is reduced substantially to a liquid whilst with additive an elastic gel is formed.

Example 8

Retorted gels as formed in example 7 (a and b) were removed from the can and rested on a perforated plate above a funnel. The liquid collected over a period of twelve hours was recorded as the amount of free water.

With no additive (7a) a 220g gel produced 29ml of free water whilst a similar gel with additive (7b) produced 11ml of free water. This illustrates that the additive decreased the syneresis of the gel.

Example 9

Guar gum was mixed for 30 seconds with Sorenson's buffer, pH 7.0, at room temperature using the Silverson Homogenizer at maximum speed. The viscosity of the resulting solution was estimated using the Brookfield viscometer model LVT-spindle 1. The viscosity of the guar gum with no additives and with an additive comprising 400 ppm sodium sulphite and 250 ppm propyi gallate were tested with time, and the results illustrated in figure 8 in which V is the time in minutes since the commencement of mixing, W is the speed of the viscometer (rpm) , X is the viscosity (cp) of the gum without additive and Y is the viscosity (cp) of the gum with additive. This example illustrates that the additives enhance the rate of development of viscosity.

Example 10

A sample of minced beef and onions were thickened by a solution of guar gum. To one portion of this was added an additive of 125 ppm sodium sulphite and 75 ppm propyi gallate. After retorting this produced a viscosity of approximately three times that of a portion without the additive. This illustrates the effectiveness of the additives with food products.

There are thus described above performance enhancing additives for polysaccharides which produce increased stability and other improvements such as reduced syneresis, increased hydration rate and improved viscosity development. These additives are effective with neutral polysaccharides at relatively low concentrations. It is to be appreciated that these additives can be used with polysaccharides other than those described and may be used to enhance gel strengths of mixed polysaccharide systems such as may be used in the food industry, which can be particularly important when heating is required for sterilization of foods. Mixed gel systems are used in many other fields such as in air fresheners where such additives may be of assistance. These additives may also be useful for example in drilling fluids for the oil industry.

These additives may also be used when chemical derivatives of such polysaccharides are prepared, particularly where heat may be applied. Further applications may be in asphalt emulsions and in the paper industry. These additives may have an application in the pharmaceutical industry for thickeners for gels used to contain compounds intended for slow release into the body. As well as being usable with solutions containing polysaccharides these additives could be used in a dry powder mix. This would be particularly relevant where irradiation is involved.

It is to be appreciated that these additives should ot be restricted to the particular examples above nor should the materials with which they may be used be so restricted.

Claims

C l a i ms

1. A performance enhancing additive for polysaccharides characterised in that it comprises a component which is one or more of an anti-oxidant, a free radical scavenger or a free radical terminator.

2. An additive according to claim 1, characterised in that it comprises an oxygen scavenger.

3. An additive according to claim 1 or claim 2, characterised in that the component is a gallate.

4. An additive according to claim 3, characterised in that the component is propyi gallate.

5. An additive according to claim 3, characterised in that the component is octyl gallate.

6. An additive according to claim 1 or claim 2, characterised in that the component is thiourea.

7. An additive according to any of claims 3 to 6 when dependent on claim 2, characterised in that the oxygen scavenger is a sulphite.

8. An additive according to claim 7, characterised in that the oxygen scavenger is sodium sulphite. •

9. An additive according to any of claims 3 to 6 when dependent on claim 2, characterised in that the oxygen scavenger is a metabisulphite.

10. An additive according to claim 9, characterised in that the oxygen scavenger is sodium metabisulphite.

11. An additive according to any of claims 3 to 10 when dependent on claim 2, characterised in that the proportion of the component is equal to or less than that of the oxygen scavenger.

12. An additive according to claim 11, characterised in that the proportion of the comp__oπent to oxygen scavenger is in the range of 1:1 to 1:10.

13. An additive according to claim 12, characterised in that the proportion of the component to oxygen scavenger is substantially 1:3.

14. A method of enhancing the performance of a polysaccharide system, characterised in that an additive according to any of claims 1 to 13 is added to the system.

15. A method according to claim 14, characterised in that means are provided for removing the dissolved oxygen in the system.

16. A method according to claim 15, characterised in that the dissolved oxygen in the system is removed by purging with a gas.

17. A method according to claim 16, characterised in that the gas is nitrogen.

18. A method according to claim 16, characterised in that the gas is helium.

19. A method according to claim 15, characterised in that the dissolved oxygen in the system is removed by heating.

20. A method according to claim 15, characterised in that the dissolved oxygen in the system is removed by applying a vacuum.

21. A method according to any of claims 14 to 20, characterised in that the polysaccharide system comprises a neutral polysaccharide.

22. A method according to claim 21, characterised in that the polysaccharide contains beta 1-4 linked mannose units.

23. A method according to any of claims 14 to 22, characterised in that the pH of the system is maintained in the range 3-12.

24. A method according to claim 23, characterised in that the pH of the system is maintained in the range 5-10.

25. A method according to any of claims 14 to 24, characterised in that the concentrations of the constituents of the additive in the system are within the range 1-10,000 ppm.

26. A method according to claim 25, characterised in that the concentrations of the constituents of the additive in the system are within the range 20-1,000 ppm.

27. A method of enhancing the performance of a mixed gel system comprising a polysaccharide containing beta 1-4 linked mannose units and a further polysaccharide, characterised in that the method is according to any of claims 14 to 26.

28. A method according to claim 27, characterised in that the further polysaccharide comprises one of either carrageenan, agar or xanthan gum.

29. A dry powder mix of a polysaccharide and an additive, characterised in that the additive is according to to any of claims 1 to 13.

30. A mix according to claim 29, characterised in that the polysaccharide contains beta 1-4 linked mannose units.