GB2063047A - Method for the production of an acid in the form of dry powder having free-flowing properties - Google Patents

Abstract

A method of producing acid in a dry form having free-flowing properties, in which the acid is mixed with anhydrous lactose in crystallized or powdered form. Suitable acids are those in particular which are non-crystallizable at room temperature and cannot be dried by heating such as lactic acid. The powdered mixture is particularly suitable as an additive for use with dry products such as food products, medicaments and cosmetics.

Description

SPECIFICATION Method for the production of an acid in the form of dry powder having free-flowing properties This invention relates to a method of preparing acid in the form of dry powder having free-flowing properties. Such powders are described in British patent specification No. 332,597, which discloses a method for their production based on the absorption of lactic acid by solid carbohydrates, whereby it is produced in a form that can be easily dosed, in which it can be used in mixes such as those for preparing substitute mother's milk having a high degree of digestibility. A suitable carbohydrate is powdered dextrose, but the lactic acid may also be absorbed in milk powder, in which a naturally occurring carbohydrate is milk-sugar containing one molecule water of crystallization, also referred to as lactose 1 aq.

Another method is that described in Dutch patent application No. 7703510, which is productive of dry, acid, powdered products that can be easily sprinkled and contain at most 30% acid, by mixing the acid concerned with a hydrolysed starch product having a DE-value (=dextrose equivalent) of less than 1, by dissolving the carbohydrate in water, dispersing the acid in the aqueous solution, and subsequently drying in known manner, for example by spraying the liquid in a spraying tower. This method is suitable for both inorganic acids, such as phosphoric acid, and organic acids, such as lactic acid and citric acid.

These two methods, however, have the disadvantages that they are very laborious and require very expensive, special apparatus, and that careful drying is virtually always necessary to produce a reasonably suitable product. It is true that the method described in the British patent does not require first dissolving the carbohydrate, which makes it necessary to evaporate and dry a large amount of liquid, butthen the acid must be mixed with the carbohydrate in solid form very gradually to ensure homogeneous distribution of the acid over the mass, while in addition subsequent drying, preferably at reduced pressure, will always bedesirable.

We have now found that the disadvantages of the above methods can be avoided, and that dry, noncoherent powders can be prepared in a simple manner by mixing the acid in liquid form with anhydrous lactose in crystalline or powdered form. The method according to the invention is suitable in particular for the preparation of relatively free-flowing powders of acids which at normal temperature do not occur in the crystalline form, and the solutions of which can not be dried by conventional means involving heating without the acid being converted during the process.Owing to these favourable properties with regard to looseness and non-hygroscopicity, the powder produced according to the present invention is particularly suitable as an additive for use with dry products, such as food products, medicaments, cosmetics and the like where acidulation is desirable, and where the conventional solid acids, such as citric acid, fumaric acid, or glucono-A-lactone, are unsatisfactory, and where the direct admixture of liquid acids leads to undesirable effects, such as lumping. Notably, the method is suitable for bringing lactic acid into a form having good sprinkling characteristics.

Surprisingly, it was found that a free-flowing powder produced by the method of the present invention during storage absorbs moisture only to a small extent, whereas lactic acid is notorious for being highly hygroscopic in the anhydrous form. It was also found that any simple mixer is adequate for carrying out the method according to the invention.

The invention is illustrated in and by the following Examples.

Example I In a Hobart mixer, lactose and lactic acid were mixed in such quantities that always 1 kg product was produced. For every mixing ratio of acid and lactose used in this investigation, experiments were conducted both with anhydrous lactose and with normal commercial lactose of pharmaceutical quality.

In Table I, the composition of the several mixtures is given with reference to the percentage of lactic acid in the resulting product, along with an evaluation of the sprinkling characteristics of the product The lactic acid used contained 20% water and was sprayed onto the lactose.

Tablet Test % lactic Nature of Nature of number acid lactose product 1 A 10 anhydrous loose 2A 15 3A 20 1 B 10 pharmaceutical sticky 2B 15 3 B 20 As shown by Table I, all admixtures of lactic acid with anhydrous lactose produced loose products, in contrast to the admixtures of lactic acid with normal pharmaceutical lactose, which in all cases resulted in more or less sticky products. A comparison of the looseness by visual evaluation was in all cases to the advantage ofthe products based on anhydrous lactose. The two products containing 10% lactic acid were in addition compared by means of the follow ing test methods: 1. Flowability, defined as the maximum angle to the horizontal which the powder can make on a round dish (angle of repose).

2. throughflow velocity in granulate throughflow meter.

3. percentage of the powder leaving a rotating cylinder having an aperture of a given diameter.

These comparative tests gave the picture given in Table 2.

Table2 Product Flowability Throughflow Percentage velocity of of outflow 50 g 10% lactic acid with anhydrous lactose 44.2 3.5 sec. 78% 10% lactic acid with normal pharmaceutical lactose immeasurable - 12% Of the product containing 15% lactic acid with anhydrous lactose, the moisture absorption during storage was investigated at some different relative humidities (Rv). The results are shown in the accompanying graph, in which the time in hours is plotted along the X axis, and the percentage of moisture absorption along the Y axis. Although lactic acid in anhydrous condition is highly hygroscopic, the product of 15% lactic acid with an hydrous lactose turned out to absorb relatively little moisture, while the free-flowing character of the product was not lost.

Example Il In a simple domestic mixer, quantities of anhydrous lactose and 80% lactic acid were mixed to produce a quantity of 300 gram product having a lactic acid content of 10%. The product felt dry and could be easily sprinkled.

Comparative Example I Operating entirely by the procedure of Example quantities of dextrose of the commercial product Cerelose 02001 and lactic acid were mixed in the Hobart mixture.

The resulting products exhibited substantially no looseness and were highly sticky.

Comparative Example II Following the procedure of Example I, lactic acid was mixed with anhydrous dextrose type Cerelose 02402. Again, the products obtained could not be sprinkled and were sticky.

Example 111 In a 2 litre glass beaker, in which a Heidolph stirrer was placed, and which was covered with a transparentcover, a quantityofanhydrous lactose was mixed with chemicaiiy pure acetic acid, made by Merck, strength 96%. A free-flowing product was obtained, containing 15% by weight of acetic acid.

Claims (6)

1. A method of producing acid in a dry form having free-flowing properties, characterised by mixing an acid with anhydrous lactose in the crystallized or powdered form.

2. A method as claimed in claim 1, wherein the acid used is non-crystallizable at room temperature and cannot be dried by heating.

3. A method as claimed in claim I or 2, wherein the acid is lactic acid.

4. A method as claimed in claim 1, substantially as herein described with reference to any of the specific Examples.

5. A dry product having free-flowing properties and produced by the method as claimed in any of the preceding claims.

6. An acidulated, dry product produced by mix ing a dry product having free-flowing properties according to claim 5 with at least one other dry component.