Effect of infrared roasting on antioxidant activity, phenolic composition and maillard reaction products of tartary buckwheat varieties

Authors: BHINDER, SEERAT - Guru Nanak Dev University; KAUR, AMRITPAL - Guru Nanak Dev University; SINGH, BALWINDER - Khalsa College; KAUR, MANPREET - Guru Nanak Dev University; KUMARI, SUPRIYA - Guru Nanak Dev University; SINGH, NARPINDER - Guru Nanak Dev University; Yadav, Madhav

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2019
Publication Date: 1/31/2019
Citation: Bhinder, S., Kaur, A., Singh, B., Kaur, M., Kumari, S., Singh, N., Yadav, M.P. 2019. Effect of infrared roasting on antioxidant activity, phenolic composition and maillard reaction products of tartary buckwheat varieties. Food Chemistry. 285:240-251. https://doi.org/10.1016/j.foodchem.2019.01.141.
DOI: https://doi.org/10.1016/j.foodchem.2019.01.141

Interpretive Summary: Tartary buckwheat (Fagopyrum tataricum) is a minor food crop that is gaining popularity due to its unique nutritional properties. It is grown in the hilly regions of India and is known for its higher yields, even under harsh climatic conditions, compared to conventional buckwheat (Fabophurm esculentum). Tartary buckwheat is a good source of protein, fiber, resistant starch, phytosterols, and vitamins and is well known for its health-promoting benefits. Tartary buckwheat contains 25 to 50 times higher free phenolics than wheat and corn. It contains a higher amount of rutin, a flavonoid known for anti-oxidative, anti-inflammatory and hepatoprotective effects. However, the high content of flavonoid gives a distinct bitter flavor and diminishes consumer acceptability of products prepared from buckwheat grains. Tartary buckwheat also contains allergens that may have a negative impact on human health. Infrared roasting has the potential to reduce these anti-nutritional components, enhance flavor and increases the shelf life of buckwheat products. The optimization of infrared roasting time and temperature combinations will help to quantify nutrient losses that may occur. The present study compared and evaluated the effect of infrared roasting time and temperature on the functional components, especially phenolic compounds of various Tartary buckwheat varieties. In this study, we found that each buckwheat variety behaved uniquely to roasting conditions. Two buckwheat varieties (IC-341651 and IC-107994) had substantially high antioxidant properties with minimum losses after roasting. Roasting at 130 degree C and 150 degree C had little variation in terms of antioxidant properties. This study can be of great value to the Indian and US agricultural and food processing industries and also to buckwheat growers.

Technical Abstract: The effect of infrared roasting on DPPH radical scavenging capacity (RSC), total flavonoid content (TFC), total phenolic content (TPC), Maillard reaction products (MRP) and phenolic profile in eight Tartary buckwheat (Fagopyrum tataricum) varieties were investigated. For analysis, buckwheat flour was produced by milling its groats roasted at 130 degree, 150 degree and 170 degree C for 10 min. TFC (2.85-3.50 mg rutin equivalents (RE)/g) and RSC (64.20-74.29 %) decreased significantly with increase in roasting temperature. TPC (5.72-10.89 mg gallic acid equivalents (GAE)/g) remained unchanged at 130 degree C and 150 degree C but exhibited a sharp decline at 170 degree C. IC-341651 and IC-107994 had appreciably high antioxidant properties with minimum losses after roasting. The lowest fluorescence of advanced MRP (FAST) index was observed for buckwheat roasted at 130 degree C (230.76-338.55 %) and the highest at 170 degree C (420.30 to 523.72%). SMLBW-4 exhibited the lowest browning index (BI), free fluorescent intermediate compounds (FIC) and FAST index, indicating the least MRP formation. Gallic acid (45.90-86.20 mg/100g DW) and quercetin (1.19'3.87 mg/g DW) were detected in only bound and free-form, respectively. Roasting caused loss of polyphenols. Rutin (16.91'26.60 mg/g DW) was the most thermostable polyphenol, which increased slightly at 130 degree C.