Effect of Porphyra Powder on the Quality and Microstructure of Noodles

The effects of Porphyra on the processing characteristics and food quality of mixed flour (wheat flour-Porphyra powder), dough and noodle were studied by the addition 0~4% Porphyra into flour to make fresh wet noodle, which fully explored the regulation of Porphyra on noodle quality. The weakening degree of the mixed flour with Porphyra decreased by 51.38% and the dough formation time and stabilization time increased and decreased by 21.56% and 48.97% respectively, and the peak viscosity and valley viscosity decreased by 27.64% and 21.96% respectively. The elastic modulus, loss modulus and tangent value of dough were negatively correlated with the addition proportion of Porphyra. Porphyra powder endowed the noodles with a unique Porphyra flavor and green appearance in terms of macro quality, especially when the additive amount was 2% to obtain the highest sensory score. With the increasing of Porphyra powder, the hardness enhanced significantly (P<0.05), the elasticity and recovery decreased remarkably (P<0.05), as well as the cooking loss rate and water absorption increased gradually. When the dosage of Porphyra was less than 2%, the cooking loss rate of prepared noodles was lower than that of high-quality noodles. Fourier infrared analyses showed that the proportion of random curl in protein secondary structure was positively correlated with the addition level of Porphyra. The results of low field nuclear magnetic resonance (NMR) showed that the addition of Porphyra shortened the relaxation time of bound water and non-flowing water, while decreased the water fluidity of noodles. For microstructure measured by stereomicroscope and scanning electron microscopy (SEM), the surface of the patch became dark and uneven as the increasing of Porphyra addition. When the addition level was more than 2%, the gluten network structure was obviously damaged. In general, the proportion of Porphyra powder in noodles should not exceed 2% without adding quality improvers.