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Antioxidant assessment of cereal based functional beverages by NIR spectroscopy and Briggs-Rauscher's method

Introduction Functional food represent a food product that with the basic nutritional impact has beneficial effects on one or more functions of the human organism. The most popular functional foods category on world-wide market are beverages because of its convenience as well as opportunity to incorporate desirable nutrients and bioactive compounds. Beverages based on cereals are excellent sources of antioxidants, vitamins and other health-promoting substances. An extract could be drunk as a food supplement or filtrated and mixed with juices to make a drink rich in dietary fibres. Materials and methods The aim of this study was to monitor the quality of the cereal water suspensions (spelled, oats, barley, wheat, rice) immediately after preparation and after storage using two non-standard measuring methods: the near-infrared spectroscopy (NIR spectroscopy) and Briggs-Rauscher method. Predictive models were developed to assess the expected antioxidant activity patterns based on NIR spectra. The antioxidant activity was determined and expressed as inhibition time and BRAI index. Results and discussion Obtained results showed a difference in the antioxidant capacity and NIR spectra of beverages. The basic differences were observed in the range of 1300 – 1700 nm for OH and CH stretches. The lowest BRAI showed cooked rice and wheat beverages (BRAI = 0.01 mg GAE / 100 g) while the highest BRAI was determined for barley beverage (0.63 mg GAE / 100 g). NIR spectroscopy with the use of chemometrics allowed the separation of cereal based beverages according to the freshness (0-7 days storage). Predictive models have shown a strong link between the NIR spectrum and antioxidant activity (R2> 0.95) confirming the applicability of NIR spectroscopy as a relevant, accurate and fast method that can be employed as a replacement for time-consuming chemical methods in the quality control.

plant beverages; antioxidant activity; BR reaction; NIR spectroscopy; PLS modelling

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