Freeze-dried coffee powder and a method for the manufacture thereof

1. A method for the manufacture of a freeze-dried coffee powder, the method comprising:

providing a coffee extract having from 40 wt % to 55 wt % solids;

adding gas to the coffee extract in an amount of from 1 NL/kg to 5 NL/kg of coffee extract, to provide a gas-containing coffee extract at above atmospheric pressure;

depressurising the gas-containing coffee extract to form a foamed coffee extract;

cooling the foamed coffee extract to below −40° C. without shear, or with low shear, to form a frozen coffee extract,

grinding the frozen coffee extract to a powder; and

drying the powder,

wherein the step of cooling the foamed coffee extract to below −40° C. comprises:

(i) cooling the foamed coffee extract to a first temperature;

(ii) cooling the foamed coffee extract from the first temperature to a second temperature lower than the first temperature; and

(iii) cooling the foamed coffee extract from the second temperature to below −40° C.,

wherein the first temperature is 1° C. above a freezing point of the foamed coffee extract and wherein the second temperature is 3° C. below the freezing point,

wherein step (ii) has a duration of from 5 to 90 minutes.

2. The method according to claim 1 , wherein the coffee extract:

(a) has from 40 to 45 wt % solids and wherein the freezing point is from −5 to −7° C.; or

(b) has from 45 to 50 wt % solids and wherein the freezing point is from −7 to −8° C.; or

(c) has from 50 to 55 wt % solids and wherein the freezing point is from −8 to −10° C.

3. The method according to claim 1 , wherein the coffee extract has from 48 to 51 wt % solids.

4. The method according to claim 1 , wherein the low shear is less than 50 s −1 .

5. The method according to claim 1 , wherein the gas is selected from nitrogen, air, argon, nitrous oxide and carbon dioxide, or a mixture of two or more thereof.

6. The method according to claim 1 , wherein the coffee extract is at a pressure of at least 2 Bar before the gas is added to the coffee extract.

7. The method according to claim 1 , wherein depressurising the gas-containing coffee extract involves reducing the pressure of the coffee extract to 5 Bar or less.

8. The method according to claim 1 , wherein depressurising the gas-containing coffee extract involves spraying the gas-containing coffee extract.

9. The method according to claim 1 , wherein the foamed coffee extract is at atmospheric pressure before the step of cooling and has a density of from 500 to 800 g/l.

10. The method according to claim 1 , wherein the mean rate of cooling in each of steps (i) and (iii) is at least −5° C. per minute.

11. The method according to claim 1 , wherein one or more of the cooling steps (i), (ii) and (iii) are conducted as a continuous process using a conveyor.

12. The method according to claim 1 , wherein one or more of the cooling steps (i), (ii) and (iii) are conducted in a holding vessel or within a pumped cooling system.

13. The method according to claim 1 , wherein step (ii) has a duration of from 5 to 60 minutes.

14. The method according to claim 1 , wherein step (ii) has a duration of from 10 to 30 minutes.

15. The method according to claim 1 , wherein the coffee extract is at a pressure of at least 5 Bar before the gas is added to the coffee extract.

16. The method according to claim 1 , wherein the coffee extract is at a pressure of from 10 to 250 Bar before the gas is added to the coffee extract.

17. The method according to claim 1 , wherein depressurising the gas-containing coffee extract involves reducing the pressure of the coffee extract to atmospheric pressure.