Effect of enzyme active and inactive soy flours on water behavior and firming rate of gluten free breads

SERRANO-FUSTER M; SCIARINI L.S; PEREZ G.T

Viena

Simposio; Third International Symposiun on Gluten Free Cereal Products and Beverages; 2013

Internation Association of Cereal Science and Technology-ICC

Previous work in our group showed the existence of a specific interaction between native soy proteins and cassava starch that diminished starch retrogradation over storage (Sciarini et al., 2012). The objective of this work was to evaluate the effect of different soy flours on gluten free bread technological quality and shelf-life. The ingredients used for bread-making were flour and starch, shortening, salt and water. Water amount incorporated varied from one formulation to another with the aim of obtaining doughs with comparable consistencies. Two different formulations were considered. The first included rice flour (RF), cassava starch (CS), enzyme-active soy flour (ASF) and water (65%, flour and starch basis), while the second included RF, CS, enzyme-inactive soy flour (ISF) and water (80%). Bread quality was assessed by measuring specific bread volume (SBV) and crumb firmness. For shelf-life studies, breads were stored for 1, 3, 7 and 10 days at two different temperatures (25ºC and 4ºC). After these periods, crumb firmness was evaluated; crumb and crust were carefully separated and moisture content was determined. The relative crystallinity after 10 days of storage was evaluated using X ray diffractometry (XRD). Breads with ASF presented a significantly higher SBV (3.27 cm3/g) than breads with ISF (2.74 cm3/g). As expected, crumb firmness was related to SBV, the higher the SBV, the lower the firmness. Upon storage, it could be seen that formulation had a larger influence on firming rate than storage temperature. For ASF breads, firming rate was 125 g/day and 183 g/day for breads stored at 4ºC and 25ºC, respectively; whereas this value was 492 g/day and 715 g/day for ISF breads, at both temperatures. It was interesting to note that data for ASF firmness could be fitted to a straight line (R2>0.95 for both temperatures), and a plateau could not been observed even after 10 of storage. Values for ISF crumb firmness could also be fitted to a straight line, but R2 was around 0.85, partly because a plateau was reached after 7 days of storage. After 10 days, ASF breads presented a firmness of 1524 g and 2031 g (4ºC and 25ºC, respectively), while ISF had firmness values of 5449 g and 6842 g. Regarding water migration during storage, it could be seen that, opposite to firming behavior, storage temperature influenced water migration from the crumb to the crust more than did the formulation: the profile of water migration was similar for breads with different formulations at the same storage temperature, but the profiles at different temperatures were different. Storage temperature seems to have a leading role on water migration. Thus, the different firming behavior during storage could not only be explained by water migration from the crumb to the crust.  As evaluated with XRD, relative crystallinity after 10 days of storage was higher for breads with ISF than for those with ASF (≈38% and ≈30% respectively), while no differences were found between different storage temperatures. These partial results indicate that bread firming during storage is influenced by starch recrystaliization rather than by water loss from the crumb to the crust. Moreover, ASF has a great influence on crumb firming rate. The impact of soy flour on amylose/amylopectin retrogradation kinetics is still under study in our laboratory.