T 0343/00 (Cream yeast/DSM N.V.) 22-10-2002

Reasons for the Decision

Article 84 EPC

1. The appellant objected against the formulation of claim 5 as maintained by the opposition division and argued that it cannot be amended without contravening to the provisions of Article 123(3) EPC.

2. The Board is convinced that the expression "baker's yeast as claimed in any one of the claims 1 to 4" does not place the skilled person in front of insurmountable difficulties of comprehension, even if claims 1 to 4 are actually not directed to said baker's yeast, but to processes using said baker's yeast. Furthermore, the Board interprets "a cream of baker's yeast comprising 17-23 wt% dry matter" as a second definition of the baker's yeast used in the process of claim 5, the first one being represented by "baker's yeast as claimed in any one of claims 1 to 4". A comma between these two definitions may have rendered claim 5 linguistically nicer. However, linguistic aesthetic cannot render an amendment to a given claim appropriate or necessary, as long as the matter for which protection is sought in said claim can be clearly identified.

3. Therefore, in the Board's judgement, claim 5 of the main request fulfils the requirements of Article 84 EPC.

Article 54 EPC

4. The claims maintained by the opposition division are directed to processes for producing dough (claim 1) and bread or related products (claim 5) making use of a cream of yeast comprising 17-23 wt% yeast dry matter characterized by further comprising gum. However, the patent in suit defines the technical problem to be solved as to keep the yeast cream homogenous (page 2, lines 39 to 41). It can thus be deduced that the essential feature of the invention is the stabilized yeast cream.

5. Both the appellant and the respondent controversially argued on the technical meaning of "cream yeast" (or of its synonyms "cream of yeast" and "cream of baker's yeast"), which thus, before any examination of the novelty and the inventive step of the claims can take place, has to be defined by the Board giving, according to decisions T 190/99 and T 79/96 (cf supra), to this expression its broadest technically sensible meaning, while taking into account the whole disclosure of the patent and ruling out interpretations which are illogical or do not make technical sense.

6. This expression appears, on one side, to be a precisely defined technical term identifying for the skilled person involved in the field of yeast production or utilisation a slurry containing 17 to 23 wt% yeast dry matter, obtained after centrifugation of the culture broth. This definition is not only to be found in the patent in suit (page 2, lines 15 to 16), but also in document (2) (page 15, second paragraph), document (16) (page 446, second paragraph), document (17) (page 84, second paragraph), Annex 15 (page 385, last line to page 386, line 6) and Annex 19 (page 294, last paragraph).

7. On the other hand, document (2) (page 17, line 32 to page 18, line 4) mentions, besides this above mentioned definition, more general ones, apparently only referring to the viscous or creamy aspect of the slurry. This kind of more general definitions can also be found in Annex 16 (page 10, right column, lines 40 to 50), Annex 17 (page 3, right column, lines 75 to 82), document (11) (column 3, lines 40 to 49), in which this expression even refers to autolysed yeast slurry, or in document (10) in which a milky yeast suspension is produced by resuspending in water yeast cells obtained as a dry product, a wet product or as a cake (page 2, lines 14 to 30).

8. In this context, it has to be noted that these various definitions of the expression "yeast cream" mentioned above cover yeast suspensions with different physico-chemical properties. Annex (19) shows for instance that the drying step causes irreversible damages to the yeast cells, as demonstrated by the amount of leaching solids (Figure 6.20), the amount of leaching glutathione (Figure 6.21) resulting in a slackening effect on the dough (page 306) and the rupture of the cytoplasmic membrane of dried cells (page 299 to page 301, heading "Biology of Yeast Drying").

9. The Board is convinced that the skilled person, whose attitude has been defined in the established case law (Case law of the Boards of Appeal of the European Patent Office, 4th edition, 201, page 111) as being conservative, would choose the definition which is widely accepted in the concerned technical field and defines the yeast cream in a more precise manner, ie the definition mentioned in the patent in suit.

10. The appellant also argued that claim 6 as filed stated that the stabilised cream of yeast was prepared by addition of gum to compressed yeast. Although this claim was further amended so as to indicate, in its granted form, that gum was added to the cream yeast, the skilled person could, nevertheless, consider that, in the applicant/patentee's own view, a slurry containing 17 to 23 wt% yeast dry matter obtained after addition of a certain amount of an aqueous solution to a "compressed yeast" was also encompassed by the expression "yeast cream".

11. "Compressed yeast" is for the skilled person, as the expression "yeast cream", a precise technical term with a well established meaning and refers to a preparation containing 27 to 33 wt% yeast dry matter as indicated in the patent in suit (page 2, lines 16 to 20), document 16 (page 446, heading "Filtration") and Annex 19. (page 292, fourth paragraph and page 293, first sentence). On the other hand, any process lowering the aqueous content of the culture broth may be considered as resulting in a "compressed" yeast. In this interpretation, the adjective "compressed" only means that a certain amount of aqueous medium has been taken away form the yeast slurry. The Board is convinced that, here again, the skilled person would take the whole disclosure of the patent in suit into account and would notice that on page 2, lines 20 to 22 "compressed yeast" is said to require refrigeration for storage and to only last for 2 to 3 weeks before loosing its leavening quality, increasing its bacterial contamination and even autolysing. This is also confirmed by the teaching of Annex 19 on page 295 (heading "Stability of Compressed Yeast"), reflecting as a textbook the common general knowledge of the skilled person, who would then conclude that a "compressed yeast" containing 27 to 33 wt% dry matter is not suitable for the purpose of the patent in suit (page 2 lines 50 to 51), so that the adjective "compressed" as used in claim 6 as filed cannot refer to the precisely defined technical term "compressed yeast", but has to be understood as meaning a slurry from which a certain amount of water has been taken away. In that sense, a "yeast cream" is also a compressed yeast and there is no contradiction between the expressions "yeast cream" and "compressed yeast" as used respectively in claims 1 and 6 as filed.

12. Document (2) described a rehydratable instant active dried yeast containing gum used for bread making, in which gum has been added in order to favour the re-suspension of the dry yeast in water. Having regard to the above mentioned definition of the expression "yeast cream", document (2) is not novelty-destroying for process claim 1 of the main request, since it does not use such a "yeast cream". Indeed, the examples of document (2) show that the gum has been added to the yeast filter cake obtained after dewatering a yeast cream in a filter press.

13. Document (10) concerned with a yeast suspension containing fats and oils used for bread making purpose is also not novelty-destroying, since most of the yeast concentrations mentioned on page 3 (lines 33 to 36) do not correspond to the definition of a "yeast cream". Furthermore, the "Working Example 1" states on page 9 (lines 13 to 14) that the yeast composition is prepared from a yeast suspension containing "40% by weight as live yeast". "Live yeast" is defined on page 4 (lines 18 to 23) as being a "compressed yeast" containing approximately 70% by weight of water (ie 30. wt% yeast dry matter) and hence corresponds to the conventional definition of a "compressed yeast" mentioned above (cf supra point 8). Therefore, document (10) does not use a yeast cream as in the patent in suit. Moreover, it does not disclose the crucial product of the patent in suit (cf supra point 1), ie a yeast cream with gum, but an emulsion containing both yeast and gums.

14. Therefore, the subject-matter of claims 1 to 8 of the main request fulfils the requirements of Article 54 EPC.

Article 56 EPC

15. In the Board's view, document (2) cannot be the closest prior art, since it addresses a technical problem different from that of the patent in suit. Indeed, its purpose is to favour the dispersion of resolubilized dry yeast and hence to avoid the clumping of the dry yeast cells brought back into suspension. This problem arises from the habit of many consumers and/or bakers to first rehydrate the instant active dry yeast before mixing it with flour and other dough or batter ingredients, which results in a substantial decrease in the leavening activity of said instant-type active dry yeast. It thus much more concerns the wetting of the yeast cells and the destruction of the forces holding them together. Furthermore, there is no indication in document (2) on the durability of the suspension obtained, which is an important element of the patent in suit, the examples of which use a time period of 10 and 13 days as a reference. It has even to be considered with scepticism whether durability is at all an issue for document (2). Indeed, the problem addressed to by document (2) relates to the baker's need for a yeast composition which can be re-suspended quickly or as defined on page 4 (line 22) "...within a reasonable amount of time..." and document (2) shows in the paragraph between page 10, line 22 and page 11, line 20 that this yeast suspension is then used immediately after its rehydration for bread-making.

16. Document (10) is considered by the Board as the closest prior art, since, as the patent in suit, it addresses inter alia the problem of rationalizing and automatizing the process of bread-making (page 3, lines 4 to 6) implying an automatic dosage of the yeast amount needed (page 3, lines 15 to 22). This problem is solved by providing a stable and fluid yeast composition, said composition being an oil in water emulsion (page 3, lines 24 to 32) containing yeast cells. Several kinds of emulsion stabilizers are cited on page 5 (lines 21 to 28), among them gums.

17. The objective technical problem in view of document (10) is the provision of an alternative to the yeast composition described therein. Compared to document (10), claim 1 of the main request can be considered as solving the problem of the stability of the yeast suspension by providing the skilled person with a method based on the sole addition of gums to the yeast slurry. The description of the patent in suit, in particular the examples, makes it plausible, in view of the conclusions reached below (cf paragraph 19) on the question of the breadth of the claims in relation to the teaching of the patent in suit, that this problem has been solved.

18. For the assessment of inventive step the question thus needs to be answered whether the skilled person starting from document (10) would derive a solution from the prior art in an obvious manner, which falls within the scope of claim 1 of the main request.

19. In the Board's opinion this question has to be negatively answered, since gums are used in document (10) not to prevent the yeast cells present in the emulsion to settle down and thus to provide a reliably constant homogenous yeast cream, but as stabilizers of the emulsion (page 5, lines 21 to 28). It is the emulsion through its increased viscosity, which in document (10) solves the problem, not the gums, so that, in fact, document (10) even teaches away from the solution disclosed in claim 1 of the main request. Furthermore, gums represent only one possibility among many other cited stabilizers and document (10) does not give any incentive why the use of gums as a stabilizer should be preferred.

20. As suggested by the appellant, document (18) or Annex (19) which reflect the common general knowledge of the skilled person may also be considered as the closest prior art, instead of document (10). Document (18), seen as a whole, and Annex (19) in the paragraph bridging pages 294 and 295 show that attempts had already been made to use yeast cream in bread-making processes. However, this use was restricted by some drawbacks, such as the necessity of continuously stirring/pumping and cooling the yeast slurry. The problem to be solved in view of document (18) or Annex (19) could be defined as the provision of an alternative method to the stirring/pumping and cooling. The question to be answered for the assessment of inventive step is whether the skilled person would have found in the prior art an incentive leading in an obvious manner to the solution proposed in the claims of the main request, ie the use of gums.

21. In the Board's view a negative answer has also to be given to this question. Gums were known as thickeners or stabilizers for suspensions or emulsions (cf documents (14) and (15), which as reviews on xanthan gum reflect the common general knowledge of the skilled person). However, as far as the interaction of gums with living material, such as yeast cells, is concerned, whereas no information can be retrieved from documents (14) and (15), document (13) even teaches away from the use of gums, since xanthan is said to interact with proteins, so that, in the case of citrus pulp and milk proteins, a flocculation and a grainy precipitate respectively occur (page 84). An interaction with proteins is also mentioned on page 86 in the paragraph concerning bakery products. Xanthan has thus exactly the opposite effect to that expected and obtained in the patent in suit.

22. According to the appellant, the results shown in the Examples 1 to 4 demonstrate that embodiments covered by the claims do not solve the technical problem underlying the patent in suit, since a homogenous yeast cream is not obtained with all the gums at all the concentrations mentioned, so that in view of decision T 939/92 (cf supra) the requirements of Article 56 EPC were not met. Appellant's view is in the Board's opinion based on a misinterpretation of said Examples, the purpose of which is in fact twofold. They aim not only at demonstrating that a homogenous yeast cream can be obtained (Example 1: third and fourth xanthan concentrations, Example 2: first guar concentration, Example 3: first and second tragacanth concentrations), but also at providing the skilled person with a guiding teaching to be adapted to the specific needs he/she may encounter. This aspect is addressed to in said examples by first defining the maximum amount of decantation obtained after 10 or 13 days of storage in the absence of gum (Example 1) and then showing the effect of given gum concentrations on the homogeneity of the yeast cream during this period of time. The skilled person, using said examples as a kind of reference curve, is then able to define (in case with a few additional routine trials) the nature and the concentration of the gum necessary for solving his/her own particular problem. The present situation is therefore different from that of decision T 939/92 (cf supra), in which a specific technical effect was not to be reasonably ascribed to the whole spectrum of chemical structures covered by the claims. Therefore, the conclusions of T 939/92 do not apply here.

23. The Board is thus of the opinion that the skilled person would not have come in an obvious manner to the solution proposed in claims 1 and 5 of the main request, the scope of which is commensurate to the teaching of the patent in suit. Therefore, claims 1 and 5. meet the requirements of Article 56 EPC. This conclusion also applies mutatis mutandis to claims 2 to 4. and 6 to 8 of the main request.