Effects of particle size and moisture content of maize grits on physical properties of expanded snacks

The main aim of this research was to investigate the effects of simultaneous changing of maize grits particle size and moisture content on some physical properties and microstructure of the expanded snacks produced by an industrial single screw extruder. Maize grits with different particle sizes of 212-299, 300-474, 475-680, 681-870, 871-1,016, and 1,017-1,070 μm and various moisture contents of 15, 16, 17, and 18% were used to manufacture puffed products. The samples produced with larger particle sizes and higher moisture content exhibited lower water absorption and water solubility indices and less expansion and crispiness than other samples. As microstructure results revealed, these samples showed more uneven surface and thicker cross-section. Overall, controlling both moisture content and particle size of maize grits had significant effects on the quality of the snacks. However, the impact of changing particle size on the snack properties was greater than changing the moisture content. This research has implications in food industry in production of puffed snacks using extrusion process. The results provide practical and green methods of improving the quality of the snacks by choosing the appropriate feed particle size and moisture content. The approach introduced in this paper is easy to impediment in the food industry without the need to change extruder configuration or adding to the list of ingredients and additives.

Preparation and application of macromolecules with a fluorescence effect in polymer processing

In this study, 9-anthracenemethyl methacrylate (AMMA) and styrene (St) as monomers and benzoyl peroxide as an initiator were used to synthesize P(St-co-AMMA), a macromolecule tracer with a fluorescence effect, via free radical copolymerization. A fluorescent online detection device was built on the basis of the principle of fluorescence online detection by using the single-screw extrusion platform of a torque rheometer to explore the effect of the amount of macromolecular tracer and screw speed on the residence time distribution of polystyrene in single-screw extrusion. Fourier transform infrared spectroscopy, ¹H-NMR, thermal stability, fluorescence properties, and rheological properties show that the resulting product P(St-co-AMMA) has a degree of thermal stability, fluorescence, and rheological properties similar to polystyrene, so this product can be used to characterize the residence time distribution during single-screw extrusion. The amount of macromolecular tracer P(St-co-AMMA) does not affect the residence time distribution of polystyrene during single-screw extrusion processing, meanwhile, the minimum residence time decreases and the residence time distribution becomes narrow as the screw speed increases, that is, the axial mixing capacity of the single-screw extruder decreases as the screw speed increases.

Effect of feed moisture, extrusion temperature and screw speed on properties of soy white flakes based aquafeed: a response surface analysis

BACKGROUND

Soy white flakes (SWF) is an intermediate product during soy bean processing. It is an untoasted inexpensive product and contains around 51% of crude protein. It can be a potential source of protein to replace fish meal for developing aquafeed. The extrusion process is versatile and is used for the development of aquafeed. Our objective was to study the effects of inclusion of SWF (up to 50%) and other extrusion processing parameters such as barrel temperature and screw speed on the properties of aquafeed extrudates using a single-screw extruder.

RESULTS

Extrudate properties, including pellet durability index, bulk density, water absorption and solubility indices and mass flow rate, were significantly (P < 0.05) affected by the process variables. SWF was the most significant variable with quadratic effects on most of the properties. Increasing temperature and screw speed resulted in increase in durability and mass flow rate of extrudates. Response surface regression models were established to correlate the properties of extrudates to the process variables.

CONCLUSION

SWF was used as an alternative protein source of fish meal. Our study shows that aquafeed with high durability, lower bulk density and lower water absorption and higher solubility indices can be obtained by adding SWF up to 40%.