Croissants are one of the great breakfast treats especially of the continental kind ! It belongs to the Viennoiserie group of baked goods, distinguished by having either a diamond or crescent shape. It is composed of fine layers of yeast-leavened dough interleaved with similar butter layers, rolled and folded many times to create a sheet – a laminate, similar to puff pastry. They come in various levels of quality. The diamond shaped variant is often associated with all-butter composition and better quality ingredients than those in a croissant shape.
Shelf-Life Times
♦ Kept at room temperature – just up to 3 days !
♦ If kept in the refrigerator, about 7 days.
♦ When frozen, use within 2 months as leaving them longer encourages a pasty-like, soft texture on thawing.
It’s quite noticeable that there is only a limited shelf-life for a croissant. Kept too long, they become stale and dry. Methods to extend the shelf-life have involved developing frozen forms that can be thawed before consumption, others have sought preservatives or added fibre to extend shelf-life.
As well as the use of oxidising flour improvers which oxidise cysteine residues in proteins to form disulphide links, the use of other cross-linking agents has many benefits. One interesting additive is that of microbial transglutaminase. Its addition appears to improve the strength of the laminated dough sheets. The enzyme catalyses the formation of covalent cross-links in various proteins (Nonaka et al., 1989). As well as improving bread quality it had the benefit of improving the volume of the croissants even after freeze-thawing (Gerrard et al., 2000).
The addition of the enzyme glucose oxidase also improves cross-linking specifically of the water-soluble fractions such as albumin and glutenin (Rasiah et al., 2005). Some studies claim to marginally improve volume but this more associated with breads where the enzyme is used more effectively.
The addition of skim milk and whey protein mixtures are also possible but require careful proportioning to achieve shelf-life improvements. FoodWrite, as well as improving the shelf-lives of other baked products has been checking various dough formulations and flours with a local bakery to reduce rapid drying and improve shelf-life in croissants. The idea is to test different flour types including whole meal in bread makers to produce a dough which is then formed into a laminate for puff pastry but can be applied to other baked goods.
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References
Gerrard, J. A., Newberry, M. P., Ross, M., Wilson, A. J., Fayle, S. E., Kavale, S. (2000) Pastry lift and croissant volume as affected by microbial transglutaminase. J. Food Sci. 65 pp. 312-314.
Nonaka, M., Tanaka, H., Okiyama, A., Motoki, M., Ando, H., Urneda, K., Matsura, A. (1989) Polymerisation of several proteins by Ca 2+-independent transglutaminase derived from micromicroorganisms. Agric. Biol. Chem. 53 pp. 2619-2623.
Hi there could you please explain the mechanism of why viennoiserie keeps longer in thr fridge than ambient? My general understanding of baked products was that chilling increased the rate of crystallization of gluten (stailing). I presume that this is due the significantly higher fat content in these products vs normal bread.
Hi Rob,
Given that the quickest way to stale bread, is to place it in the fridge, then you would think the same would happen to croissants, or indeed to Danish pastries. Both product types contain wheat flour so it would be intuitive to think they both stale in the same manner when cooled in a refrigerator. It is apparent from the research and from personal experience this just isn’t the situation.
It’s well known that a few mechanisms are involved in the bread and pastry staling process. As you probably know anyway, the major issue is the way starch or rather amylopectin undergoes retrogradation. Generally, the starch molecules alter in structure during and following the baking process. The starch gelatinises and the amylopectin chains which have altered structure realign during the cooling process. There is also change in water binding associated with this realignment. The other less apparent staling mechanism is due to water movement within the dough during and after baking but that too is wrapped up in the physical and to a large extent, the chemical structure of each baked product. Both these processes are occurring to differing extents in the dough whatever the product.
Croissants are prepared differently to bread for a start. There is a significant degree of difference in the ingredients and how the croissant is prepared. Harder flour tends to be used in a croissant than in bread generally, which implies the protein and certainly the wheat gluten content is higher. Croissants are also prepared from puff pastry which is highly laminated, relying on the fat to maintain layer separation.
It seems viennoiserie products undergo a different staling process which is not maximised by keeping at a fridge temperature or indeed anywhere between 0 and 8 °C. In a typical baking process, when the flour is mixed with water, the proteins are bound into a continuous gluten matrix which binds the starch granules. Further processing by whatever means creates a dough of appropriate elasticity, cohesion and extensibility. This is then fashioned into the croissant dough. This type of process is supposedly not so evident in a bread dough. The role of gluten is complex here but in a croissant during the baking process, it is supposed to modify the amylopectin molecules making them less susceptible to retrogradation (supposedly but not the full picture).
We know during baking that moisture in the dough turns to steam but unlike a bread, cannot escape so easily because the fat layers are impervious to their movement. A build up of steam pressure forces the layers to separate from each other hence the puff. In croissant and Danish pastes, the effect of steam pressure is also aided by the release of carbon dioxide from yeast fermentation. I’m not sure what proportion of water is retained however without recourse to the research papers.
In the same baking process for croissants, the laminating fat melts and is absorbed into the dough. The croissant has a softer texture and is resistant to further moisture addition. I think it’s important to note that keeping the croissants wrapped up prevents water gain because puff pastry is hygroscopic, will pick up moisture but unlike bread becomes chewy and tough rather than hard and drier like bread.
Hope this helps explain the situation to a certain extent. There is a fuller molecular explanation but that would be an essay. I’m also interested to hear views from others as this doesn’t explain all the features of staling.