Abstract
Rice (Oryza sativa L.) is a major staple food for the majority of the world population. Grown and harvested as paddy, it is present on our tables as white rice (milled), brown rice (dehusked) or, after being subjected to thermal processes, as parboiled rice. Recently, pigmented varieties are also appreciated (red and black rice). In this study, we evaluated proximate composition, polyphenol content and anti-inflammatory properties of Italian pigmented rice varieties and bran as well as white rice in different processed forms (milled, parboiled and integral), in order to assess the nutritional and antioxidant properties of Italian rice varieties and their capacity to reduce inflammation. Our results showed that pigmented rice varieties displayed high antioxidant capacity along with the highest flavonoid and polyphenol content. Anthocyanins were mainly present in black rice, whereas alkylresorcinols were found only in red rice. Rice bran proved to be particularly rich in carotenoids. The evaluation of the anti-inflammatory properties using lipopolysaccharide (LPS)-induced mouse RAW 264.7 macrophages pre-treated with extracts obtained from integral, black, red rice and bran showed that the expression of inducible Nitric Oxide Synthase (iNOS) was specifically reduced at both transcript and protein level by extracts, indicating the capacity of rice extracts to modulate the inflammatory response.
Highlights
Rice is the third most important cereal food in the world and the staple food in many Asian countries
The most common rice consumed by humans is white rice, but an increasing interest emerged around pigmented rice varieties, such as black, red and dark purple rice, due to the considerable amount of polyphenols present in the external layers of rice kernels
To measure the digestible starch, the supernatants obtained by the three initial centrifugations were combined, the volume adjusted to 100 mL with 100 mM sodium acetate buffer pH 4.5 and a 0.1 mL aliquot was incubated with 10 μL of amyloglucosidase solution (300 U/mL) for 20 min at 50°C
Summary
Rice is the third most important cereal food in the world and the staple food in many Asian countries. Referred to as milled or polished rice, is obtained by removing 8-10% of external layers (mainly bran) from brown rice [7]. Parboiling of rice is an effective processing technique to Universal Journal of Agricultural Research 5(5): 312-321, 2017 increase storage stability of rice with minimal changes in nutritional properties. Resistant starch from rice has the potential to improve human health; its content in commonly consumed rice cultivars or pigmented rice varieties needs further characterization. The present study aimed at characterizing the proximate composition, polyphenol content and anti-inflammatory properties of Italian pigmented rice varieties and bran as well as white rice in different processed forms (milled, parboiled and integral), in order to assess the nutritional and antioxidant properties of Italian rice varieties and their capacity to reduce inflammation
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