INFLUENCE OF DIFFERENT TECHNOLOGICAL TREATMENTS ON PHENOLIC PROFILE AND ANTIOXIDANT ACTIVITY OF PIGMENTED RICE (ORYZA SATIVA L.)
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Data di Pubblicazione:
2022
Citazione:
INFLUENCE OF DIFFERENT TECHNOLOGICAL TREATMENTS ON PHENOLIC PROFILE AND
ANTIOXIDANT ACTIVITY OF PIGMENTED RICE (ORYZA SATIVA L.) / C. Bani, C.M. DI LORENZO, S. Biella, M. Magni, F. Mercogliano, P.A. Restani, F. Colombo. ((Intervento presentato al 1. convegno Italian School in Food Chemistry for PhD student tenutosi a Pavia : 17-18 ottobre nel 2022.
Abstract:
Introduction
Pigmented rice varieties are rich in polyphenols, such as flavonoids, anthocyanins and proanthocyanidins, with known antioxidant and anti-inflammatory effects. Although more interesting from the functional point of view, the pigmented varieties require long cooking times compared to non-pigmented ones. As a
consequence, different technological treatments, such as milling or parboiling, have been applied to these
cereals to reduce the cooking time. These treatments could have positive effects on the nutritional value of
rice: for example, parboiling process increases the concentration of tocotrienols, tocopherols, and γ-
oryzanol. On the other hand, few studies have evaluated their impact on phenolic compounds. The purpose
of this study was the evaluation of the effects of two technological treatments (milling and parboiling) on the
phenolic profile and antioxidant capacity of different pigmented rice varieties.
Materials and Methods
Samples of rice with different pigmentation and subjected to different technological treatments were
included in this study and compared with some by-products of rice processing (bran) (Table 1). After the
harvest, rice was dehulled to obtained brown rice. Subsequently, the milling procedure could be applied as
additional step, obtaining milled rice and bran. The samples were provided by Azienda Agricola Bertolone
Eleonora di Bertolone Giovanni (Violet, Orange and Carnaroli) or found in the Italian market (Venere and Ermes).
The flours, obtain by grinding samples, were stored under vacuum, in the dark, at 4°C until further analysis.
Two extraction methods were applied for the quantification of the free phenolic compounds and total
anthocyanins [Catena et al., 2019; Colombo et al., 2021]. Different in vitro methods were applied to evaluate
their phenolic profile and the antioxidant activity: 1) the Folin-Ciocalteu assay, for the evaluation of the
content of total phenolics; 2) the pH differential method, for the determination of total anthocyanins (applied
exclusively to Violet and Venere samples); 3) the DPPH assay, to evaluate the total antioxidant capacity.
Moreover, it was applied the use of HPTLC technique (High Performance Thin Layer Chromatography) allowed the characterization of phenolic profile and, after derivatization with DPPH reagent, the evaluation of relative antioxidant capacity.
Results and Discussion
The content of soluble polyphenol compounds (SPC) ranged between 0.28±0.02 and 5.69±0.62 mg equivalents of gallic acid (GAE)/g; as expected brown, purple and black varieties showed the highest SPC (5.69±0.62 mg GAE/g and 3.42±0.40 mg GAE/g, respectively). In all samples considered the technological treatments of parboiling and milling determined a reduction of SPC. The milling process resulted in reductions of -46%, -70%, and -77% for Carnaroli, Violet, and Orange, respectively. The parboiling process was responsible for a reduction of SPC corresponding to -32% and -74% for Orange and Violet, respectively. Considering that phenolic compounds are mainly concentrated in the outer layers of rice, the bran obtained from the milling process showed a phenol content from 6 to 9 fold higher than that of the corresponding whole rice. In agreement with the values obtained for SPC, the brown, purple and black varieties showed the highest antioxidant capacity (AOA) (1.65±0.11 and 1.07±0.11 mg GAE/g, respectively) followed by the orange and red ones (0.25±0.01 and 0.33±0.11 mg GAE/g) and the unpigmented variety (0.14±0.02 mg GAE/g). According to SPC, the technological treatments (parboiling and milling) negatively influenced AOA, determining a reduction between -32% and -76%. Finally, brown violet rice showed the highest anthocyanin content (2.40±0.19 mg e
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Elenco autori:
C. Bani, C.M. DI LORENZO, S. Biella, M. Magni, F. Mercogliano, P.A. Restani, F. Colombo
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