Modelling and experimental studies for quality changes in tortilla chips during baking
The overall goal of this research was to investigate the quality changes in tortilla chips during baking and predict product properties as a function of baking conditions. Chemical, rheological and structural changes occur within the tortilla chips during baking. Moisture content of a product has an important impact on the final properties of foods while these changes occur. Moisture diffusion was described using Fick's law of diffusion. Average effective diffusivity coefficient (Deff) of samples was determined from continuous weight determination. It was in the range from 6.25 × 10−10 to 10.98 × 10−10 m2/s. It was found that Deff had an Arrhenius type of dependency with respect to temperature. Textural properties of samples with respect to baking conditions were investigated using a texture analyzer. Textural properties showed similar trends for each baking temperature in which they increased with baking time until they reached a maximum then decreased. The fracture force of samples baked at 561 K was 760 N after 180 s, it reached to 1378 N after 240 s, and it decreased to 734 N after 280 s. Microstructure of samples obtained using scanning electron microscopy showed that cracks became larger for the samples baked longer times that made them weaker against the breaking force. Glass transition temperature (Tg) of samples was investigated by dynamic mechanical thermal analyzer. Tg of samples increased linearly with increasing baking time for each temperature at constant moisture content. Tg range was 59.64°C to 71.44°C for samples baked at 533 K. The effect of emulsifier on textural properties and moisture content of tortilla chips were studied. The emulsifier was added to formulation 0.5–5.0% range. The fracturability and hardness values of samples with mono- and diglycerides up to 3.0% were significantly (P < 0.5) different than that of control samples. There was a negative relationship between textural properties of samples and the emulsifier content. With increasing emulsifier content, the fracturability and hardness values decreased. The fracture force was 1219 N and 891 N for the samples with 0.5 and 5% mono- and diglycerides, respectively. The hardness changed from 2.00 to 1.40 Nm for the same samples.
Singh, Purdue University.
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