Quantitative, multi-scale imaging of the layered structure in puff pastry
Imagerie quantitative, multi-échelle des couches alternées dans la pâte feuilletée
Deligny, C. ; Bousquières, J. ; Collewet, G. ; Challois, S. ; Riaublanc, A. ; Lucas, T.
Type de document
Communication scientifique avec actes
Affiliation de l'auteur
IRSTEA RENNES UR TERE FRA ; IRSTEA RENNES UR TERE FRA ; IRSTEA RENNES UR TERE FRA ; IRSTEA RENNES UR TERE FRA ; INRA UR 1268 BIOPOLYMERES INTERACT ASSEMBLAGES NANTES FRA ; IRSTEA RENNES UR TERE FRA
Résumé / Abstract
Puff pastry is characterized by a light and flaky texture due to its unique combination of fat and dough in a layered structure. Lamination and sheeting are combined to create multiple layers. It is commonly believed that the continuity of the layers is a feature essential to achieve the desirable texture after baking. The decrease of pastry volume at high numbers of sheets was indeed related to the occurrence of breakage, and the consecutive loss of the impervious function of fat layers. Such mechanism as well as the relevant size of ruptures, the localization of bubbles relative to fat… lack of experimental evidence however. The aim of the present study was to apply imaging techniques and image analysis (implying quantification) to better understand the development of these structures (layers and bubbles) in croissant (4-81 layers). A multi-scale study was attempted by combining techniques with distinct spatial resolutions: Confocal Laser Scanning Microscopy CLSM (pixel size 0.6µm, field of view 4mm), and Magnetic Resonance Imaging MRI (pixel size 500µm, field of view 10cm compatible with the product dimensions). CLSM was applied to pastry after sheeting. Thickness along each layer (fat and dough), number of fat layers, and number of ruptures in fat layers were calculated after thresholding and labeling of fat layers. MRI (1.5T) was applied to pastry during proving. Contrast between protons from fat and water was achieved by density and T2 weighting (T1 were close). Maps of gas, fat and dough content were calculated using a dedicated algorithm. The measured number of fat layers was proportional to the expected number, although lower by 10%. Missing fat layers in CLSM images were attributed to large-sized ruptures, from a few mm to a few cm, and related to the signal disappearance of large fat portions in MRI images; the lowest thickness of fat measurable with MRI was estimated using synthetic images with variable thickness of fat layers and was used in the discussion of results. Variability between CLSM samples from the same pastry sheet gave additional evidence. However, the effect of these large-sized ruptures could not explain the decrease in pastry volume at high numbers of sheet. On the contrary, the proportion of fat fragments increased drastically at high number of sheets and could be related lower capability to gas retention. The features of dough layers (elastic recovery after sheeting, bubble inflation during proving) will also be presented.
Inside-Food, 04/04/2013 - 09/04/2013, Leuven, BEL