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Description:
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Antistaling properties of enzymes (xylanase , bacterial maltogenic and conventional a -amylases ) , CMC and vital wheat gluten on corn tortillas were evaluated during storage for up to 21 days . Effect of storage time (0 -21 days ) and temperature ( -40 , -20 , 3 , 10 and 21 oC ) on tortilla staling was evaluated with or without additives .
Addition of 275 -1650 AU of ICS maltogenic amylase effectively reduced amylopectin retrogradation without reducing tortilla yields , but did not improve tortilla flexibility .
The combination of 825 AU of ICS amylase (to interfere with intra -granular amylopectin re -crystallization ) and 0 .25 % CMC (to create a more flexible inter -granular matrix than retrograded amylose ) produced less stiff , equally flexible and less chewy tortillas than 0 .5 % CMC .
Corn tortilla staling followed the basic laws that control aging in starch -based semi -crystalline systems such as starch gels , bread and other baked products . Amylopectin re -crystallization was the driving force behind the staling of corn tortillas . Increasing levels of re -crystallized amylopectin measured by DSC correlated significantly with increased tortilla stiffness and reduction in tortilla rollability , pliability and rupture distance during storage .
Re -crystallization of amylopectin in fresh tortillas was not detected . It increased rapidly during the first 24 hr reaching a plateau after 7 days storage . The level of amylopectin re -crystallization on tortillas showed a bell -shaped trend along the evaluated storage temperature range with a maximum around 7 oC .
However , a negative linear relationship of peak pasting viscosity with storage temperature of tortilla extracts without additives after 21 days suggests other compounds besides amylopectin affect tortilla staling . Thus , interfering with amylopectin re -crystallization is not the only way to retard staling .
Further research is required to optimize the addition of maltogenic amylases in continuous processing lines that use fresh masa instead of nixtamalized corn flour , to determine how these amylases interfere with amylopectin re -crystallization and to elucidate if amylose retrogradation continues during storage and plays a role in tortilla staling . |