Maybe the following can be usefull also...
Layered Doughs
"In many bakery products, fat is layered between sheets and dough, and this is manipulated to make a dough sheet consisting of up to 100 alternating layers of dough and fat. Such roll-in doughs include Danish pastry, puff pastry and croissants. The dough is mixed, divided into pieces of about 10 kg each, then cooled to 5-10 C in a retarder. The cooled dough is rolled out, two to three kgs of fat is spread over part of the sheet and the dough is folded over to cover the fat. The "sandwhich" is then rolled out and folded; this is repeated several times, often with a retarding step included to keep the dough/fat mass cool.
The primary goal during the roll-in process is to preserve the structure of alternate layers of dough and fat. There are several important factors to consider in selecting the correct shortening or margarine for such a process. Some of them are: solid fat index (SFI) and plasticity of the fat; complete melting point of the fat; consistency (softness) of the dough; retarder temperature; number of folds given the dough before returning it to the retarder; and proofing temperature. Many of these factors are unique to a given product in a particular bakery, and they influence the specification for the roll-in fat which gives the best final product in that bakery (Stauffer, 1996)."
Croissants
"A croissant dough is similar to Danish dough, although it generally contains somewhat less sugar and water so it is somewhat firmer at the optimum mixed dough temperature of 20 C. As with Danish, the dough pieces are usually retarded before roll-in is begun. The best quality croissants are produced using unsalted butter for roll-in. The amount used varies from 20 to 35% of dough weight; higher levers give a product that has less volume and flakiness, and is often perceived as greasy in the mouth. The optimum is usually about 25% roll-in fat.
The factors involved in successful processing are similar to those discussed above for Danish pastry. Because butter has a steeper SFI curve than all-purpose shortening (it is much harder at retarder temperatures) more care is required to prevent tearing the dough as it is being rolled. The melting point is lower than that of shortening so proofing temperatures are lower than for Danish. Puff pastry margarine is an acceptable substitute although it does not contribute as much flavor as butter. Since puff pastry margarine has a higher melting point, the proofing may be done at a higher temperature (and for shorter times) if time is a factor (Stauffer, 1996)."
Oxidation
"The rate of oxidation depends on the concentration of dissolved oxygen, the temperature, the presence of prooxidants such as copper and iron, the degree of unsaturation of the fat, and the presence of antioxidants that may retard the onset of oxidation. Compared with many fats, milk fat has a good oxidative stability, because it is high in total saturates, low in polyunsaturates and contains natural antioxidants, principally a-tocopherol.
The development of oxidative rancidity in milk fat is the major determinant of the stability of the fat on storage. Dissolved air in the milk fat can give dissolved oxygen levels of up to 40 ppm at 30 C. In practice, the dissolved oxygen level in the freshly processed milk fat would be about 5 ppm at 45 C, a level sufficient to permit the development of oxidative rancidity, but if the milk fat were allowed to equilibrate with the air, then this level could increase to 33 ppm with a consequent increase in the rate of development of oxidative rancidity. The solubility curve for oxygen in milk fat is a compound of solubility curves for the liquid and solid phases (Figure 1.7, page 28 in the book). Though the solubility decreases with increasing temperature for both phases, the solubility of oxygen in the liquid phase is much higher than for the closely packed solid phase (Hettinga, 1996)."
Clyde E. Stauffer, 1996, Oils and Fats in Bakery Products In: Bailey's Industrial Oil and Fat Products, Volume 3, Edible Oil and Fat Products: Products and Application Technology, Y. H. Hui, Wiley-Interscience Publication.
David Hettinga, 1996, Butter In: Bailey's Industrial Oil and Fat Products, Volume 3, Edible Oil and Fat Products: Products and Application Technology, Y. H. Hui, Wiley-Interscience Publication.