Very Rice Results: Particle Size Analysis of Rice Derivatives

The particle size distributions (PSD) of rice milk, rice flour and rice proteins were characterized with the PSA in liquid and dry mode. The PSD of rice milk displays a major peak at 6 μm likely representing starch granules, while that of rice proteins shows a major peak around 50 μm likely corresponding to protein aggregates. Rice flour showed a bimodal profile indicating the presence of both starch and proteins.

Rice (Oryza sativa) is a staple food for more than half of humanity, and is not only and a major source of nutritional carbohydrates but also of proteins.
Starch is the major component of rice, accounting for over 80 % of constituents. Rice starch is organized in polyhedral, irregular granules whose particle size varies between 2 and 7 μm, making them the smallest starch granules from all cereals.
Protein content of rice grains accounts for under 10 % of the mass, but proteins extracted from the seed, and even more from rice bran, have a superior nutritional quality compared to other cereal-derived proteins. Their amino acid score - a measure of the balance between the different amino acids in relation to human nutritional needs - can reach 95 % and is thus comparable to the score of soy and dairy products, which is close to 100 %. The major rice proteins (albumin, glutelin, globulin, and prolamin) are also unrelated to gluten, making Oryza sativa a hypoallergenic alternative to other cereals.
Because of these health advantages and the widespread availability of the basis product, rice derivatives such as rice milk, flour, and extracted proteins are increasingly used in the fast-growing market of gluten-free and plant-based food alternatives. Manufacturing processes often involve several milling steps followed by complex physical and/or chemical extraction steps. This leads to a potentially high variability of the resulting product, highlighting the need for a strict quality control process along the manufacturing chain.
Here we show how Anton Paar’s PSA, which determines the particle size distribution of either dry powders or liquid suspensions by laser diffraction, can be used in this context.

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