“1H Low Resolution NMR proved to be an efficient technique to study and describe pasta structure and quality”
Dried pasta can be readily stored and used to make a variety of easy-to-prepare meals. Consequently, it has become a popular foodstuff in many countries around the world. It is typically produced from a mixture of durum wheat semolina and water. However, with increasing demand from consumers with specific dietary requirements, such as gluten-free, pasta is now also made from non-wheat alternatives. These may include whole grains, vegetables and legumes.
The structure of the final pasta, and so also its quality, is determined by the nature of the raw materials and the processing methodology. It is further impacted by the effects of heat and water on the structure and state of the pasta during cooking. It is important to ensure that cooking does not reduce the quality of the pasta to such an extent that it becomes unacceptable to the consumer. Quality testing of pasta is thus conducted to determine its textural properties (stickiness, firmness), cooking and overcooking tolerance, water absorption, and solids loss during cooking.
Such testing is particularly important for pasta made from unconventional non-wheat ingredients, since these can significantly alter its structure and cooking qualities. The effects of novel ingredients on the macromolecular (hardness and moisture content), mesoscopic (thermal and viscoelastic properties), molecular (1H mobility) and microscopic (microstructure) properties of pasta therefore need to be evaluated.
Recently a multi-scale screening of four types of commercially available pasta formulations was performed to determine their physico-chemical properties. Time domain nuclear magnetic resonance (TD-NMR) spectroscopy using a Bruker Minispec™ spectrometer was employed to assess the proton molecular mobility of the cooked pastas. Viscoelastic behaviour was studied using dynamic mechanical analysis and texture analysis determined the firmness of the pastas. A principal component analysis was also performed to assess the usefulness of the multi-scale approach in the differentiation of different pasta formulations.
The pasta samples analysed were wheat semolina, wholewheat semolina, vegetarian, and gluten-free. The different formulations were shown to have significantly different properties. The wheat semolina and wholewheat pastas exhibited more pronounced viscoelastic behaviour, were more firm and showed higher mobility of the more rigid protons. The vegetarian pasta had the highest content of frozen water and higher molecular mobility. Gluten-free pasta had the greatest rigid population. In addition, the cooking time needed to achieve a firm, resilient and non-sticky (al dente) pasta differed between the different pasta formulations. The vegetarian and gluten-free pastas had to be cooked longer than the times indicated on the packets in order to achieve optimal moisture content.
The principal component analysis resulted in the clustering of different pastas based on all of the studied parameters. It showed that most of the NMR parameters were able to describe the different pasta formulations.
This study indicated the utility of a multi-scale approach in discriminating between different pasta formulations. In addition to describing the physico-chemical properties, TD-NMR proved to have the capability for properly discriminating different pasta formulations.
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Diantom A, et al. A multi-scale approach for pasta quality features assessment. LWT – Food Science and Technology 2019;101:285–292. https://www.sciencedirect.com/science/article/pii/S0023643818309551