PATENT CLAIMS 1. A process for the preparation of a water soluble coffee or tea product from a non-rewetted particulate material obtained from an extract by drying, characteri zed in subjecting a layer of particulate material having a substantially uniform moisture content which is higher than the moisture content desired in the final product to a heat treat¬ ment, the heat treatment being carried out essentially without affecting the moisture content of the particulate material at a combination of temperature and time being adequate for effecting fusion so as to form a compact cake-like structure, disintegrating the cake-like structure into granular material after cooling as necessary, and subjecting the granular material to final drying, optionally after separation of off-size particles. 2. A process according to claim 1, charac¬ terized in that the particulate material has been obtained from a spray drying process. 3. A process according to claim 1 or 2, cha¬ racterized in that the particulate material has been obtained from a combined spray drying and belt drying process. 4. A process according to claim 1, charac¬ terized in that the particulate material has been obtained from a freeze drying process. 5. A process according to any of claims 1 - 4, characterized in that the moisture content of the particulate material is in the range from 4-12 %, particularly in the range from 5 - 11 % and prefer¬ ably in the range from 6 - 10 % by weight. 6. A process according to any of claims 1-5, characterized in that the moisture content of the particulate material is 1 - 10%, particularly 3 - 8 % by weight (abs.) higher than the moisture content of the final product. 7. A process according to any of claims 1-6, characterized in that the heat treatment is carried out in an environment substantially in moisture equilibrium with the particulate material. 8. A process according to any of claims 1-7, characterized in that the layer of particulate material is confined between opposed barriers when the heat treatment is carried out. 9. A process according to claim 8, charac¬ terized in that the barriers are essentially non-pervious to gasses. 10. A process according to claim 8 or 9, char¬ acterized in that one of the opposed barriers or both are defined by or comprise an endless belt. 11. A process according to any of claims 1-10, characterized in that the layer of particulate material is supported on an endless belt or an array of trays during the heat treatment. 12. A process according to claim 11, charac - terized in that the endless belt or array of trays is moved continuously. 13. A process according to claim 11, charac - terized in that the endless belt or array of trays is moved stepwise. 14. A process according to any of claims 1 - 13, characterized in that heat is transferred to the layer of particulate material by means of conduction. 15. A process according to claim 14, charac - terized in that heat is transferred to the layer of particulate material using heating elements in contact with at least one of the barriers, belts, trays, or other supporting structures. 16. A process according to claim 15, charac - terized in that heat is supplied to the heating elements by means of electricity or a fluid medium such as hot oil, hot water or steam. 17. A process according to claim 15 or 16, c h a - racterized in that the surface temperature of the heating elements is in the range from 60 - 120 °C, particularly in the range from 60 - 90 °C. 18. A process according to any of claims 1-17, characterized in that heat is transferred to the layer of particulate material by means of radiation or convection. 19. A process according to any of claims 1-18, characterized in that heat is supplied to provide a temperature in the layer of particulate material in the range from 45 - 120 °C, particularly in the range from 50 - 90 °C. 20. A process according to any of claims 1-19, characterized in that the heat treatment is carried out for 2-30 min. 21. A process according to any of claims 1-20, characterized in that the thickness of the layer of particulate material during the heat treatment is in the range from 10 - 50 mm. 22. A process according to any of claims 1 - 21, characterized in that the heat treatment is carried out under compression of the layer. 23. A process according to claim 22, charac - terized in that the layer is compressed to 65 - 90 %, particularly 70 - 85 %, of the initial thickness during the heat treatment. 24. A process according to any of claims 1-23, characterized in that fines are separated from the granular material before final drying and recirculated to the heat treatment step. 25. A process according to any of claims 1-24, characterized in that fines are separated from the granular material before final drying and recirculated to the drying process.