The effect of enzymes and hydrocolloids on the texture of tortillas from fresh nixtamalized masa and nixtamalized corn flour

摘要

The texture of tortillas was improved by the addition of maltogenic amylase and carboxymethylcellulose (CMC) and guar gum to fresh masa from ground nixtamal (FNM) and nixtamalized corn flour (NCF) masa. Differences in the performance of additives in tortillas held under refrigeration or ambient storage were documented. For NCF tortillas, significant improvements were obtained in objective and subjective texture measurements by two treatments. Tortilla texture was improved by a treatment with a high enzyme level (170 mg/kg of maltogenic ?-amylase, 0.14% CMC, 0.85% guar) as measured by objective tests and by a treatment with low enzyme level (60 mg/kg of maltogenic ?-amylase, 0.43% CMC, 0.57% guar) as measured by subjective tests. The addition of maltogenic ?-amylase (70 mg/kg) and CMC (0.35%) to FNM tortillas at levels similar to the low enzyme NCF treatment but with lower guar level (0.12%) improved tortilla texture. The maltogenic ?-amylase softened tortillas by trimming the starch structure. This allowed the guar to interfere with amylopectin re-crystallization inside gelatinized starch granules. The CMC created a more flexible intergranular matrix that helped maintain the disrupted tortilla structure. Guar was ineffective in refrigerated tortillas, whereas, maltodextrins effectively improved refrigerated tortillas. The sequence of partial starch hydrolysis, warm holding condition, and time for guar to associate with starch and CMC was necessary to improve tortilla texture. Thus, different additives may be required for cold versus room temperature storage. Sugars increased in enzyme-treated tortillas during storage. This suggests that maltogenic ?-amylase was only partially inactivated during baking of corn tortillas. Tortillas with more enzyme had lower and later pasting viscosity as measured by a Rapid Viscoanalyzer. Tortillas prepared from FNM also had lower and later pasting viscosity compared to NCF tortillas. Pasting viscosity of tortillas revealed intrinsic starch polymer characteristics and interactions. Results of this study provide commercially applicable information about desired levels for the extent of starch hydrolysis, the type and amount of gums and starches, and product microstructure to delay staling of corn tortillas.