Measuring protein in semolina flour and durum wheat using Near Infrared Spectroscopy
by Phillip Clancy, Next Instruments, Sydney, Australia
Near Infrared Spectroscopy measures protein, moisture, oil, starch and fibre in flour, grains and oil seeds
Pasta is made using semolina, which is produced from Durum wheat. Measuring the protein and moisture in the durum wheat, the protein, moisture and ash in semolina and then the moisture and protein in the pasta is the trifecta of measurements for the pasta industry.
The issue has been that there has not been a single NIR analyser that is optimised for measuring materials in all these three parts of the process. Next Instruments has introduced the CropScan 3000F Flour and Grain Analyser as a means of achieving this trifecta and providing pasta manufacturers with a total measurement solution.
An international group of companies that specialise in pasta manufacture across the world have recently installed the CropScan 3000F into six factories in the USA and Canada. This article describes the system and how this group is using it.
Breaking it down: Semolina and pasta
Semolina is the middlings produced by separating the bran and germ from the endosperm of durum wheat. By sifting these middlings, the remaining coarse starch granules are the semolina. Grinding the semolina further will result in fine durum flour. Semolina is yellow and is very free flowing as compared with normal flour. Semolina has approximately 73 percent carbohydrates of which four percent is fibre, 12.5 percent protein, one percent fat and 12-14 percent moisture.
Pasta is made as either fresh or dried. The group manufacturers dried pasta in many factories around the world. Pasta is made by mixing water and semolina and then adding egg, vegetable juice, herbs and spices for flavour and colour.
The dough is generally steam sterilised and then rolled out into sheets for cutting or stamping, or the dough is extruded through dies to form the specific type of pasta. The dried pasta is then packaged. Fresh pasta is made either in a restaurant or at home. It is rolled out using a "pasta machine" and then cut into strips to be then boiled and eaten within hours of making the dough.
Pasta can be manufactured using other forms of flour. Likewise semolina can be used to make other food products including couscous, cream of wheat porridge, as a desert with milk, in savoury dishes etc.
The significance of the protein in semolina lies in the need for the pasta to be flexible so that the dough can be easily formed into different shapes. Durum wheat is the "hardest" wheat available and does not mill easily. As such the semolina is coarse and when made into dough it does not form the "strong" gluten bonding that occurs with bread wheat flour.
This makes the dough more malleable and can be sheeted or extruded. Durum wheat (Triticum durum) is the only tetraploid species of wheat used in the processed grain industry. Common wheats (Triticum aestivum L.) are hexaploid species and has a higher wet gluten content, which is important for developing strong dough which can support gas bubbles in bread. The optimum protein content of semolina is 12-13 percent for pasta production although higher protein content durum is used for unleavened bread and other food production.