Effects of Onion Quercetin on Oxidative Stability of Cook-chill Chicken in Vacuum-sealed Containers

Recovery of Bioactive Flavonols from Onion Solid Wastes Employing Water/Ethanol-Based Solvent Systems

Food processing by-products and wastes represent in many instances major polluting agents, since they bear a significant load of organic bio-molecules and particularly high chemical and biological oxygen demand (COD and BOD) levels. In this regard the development of processes that will aim at reducing the polluting load by removing added-value phytochemicals from agriculture-food wastes becomes imminent. In the present study, a first approach regarding the efficient recovery of bioactive flavonols from onion solid wastes has been attempted. Major flavonols were identified by liquid chromatography-mass spectrometry techniques and recovery was achieved by using environmentally friendly and food-compatible solvent systems, composed of water/ethanol, and acidified with either acetic or citric acid and HCl. Initial screening of various mixtures showed that significantly higher recoveries (P<0.001) can be attained by using 60% ethanol containing 0.1% HCl. The assessment of factors affecting yield, including extraction time and temperature, was accomplished using a series of extractions on the basis of a 3 × 3 factorial design model. The results obtained showed that maximization of yield is dependent upon increasing both extraction time and temperature.

Food content, processing, absorption and metabolism of onion flavonoids

The question as to how far the development of chronic diseases in humans depends on diet still remains open. Simultaneously, epidemiological studies suggest the consumption of a flavonoids rich diet might decrease the risk of degenerative changes and certain diseases. The intake of this group of compounds as to quality and quantity depends on dietary habits and a widespread presence of quercetin in the diet makes this compound one of the key factors. Onion, one of the richest and most common quercetin sources, was particularly often studied in different aspects. Quercetin is present in onion mainly as glycosides, of which the distribution within the onion bulb changes in onion processing, and biological activities attracted a lot of attention. Especially antioxidative activity demonstrated in vitro was initially associated with most of the beneficial effects of quercetin on the human body. However, after ingestion quercetin undergoes extensive metabolism and microbial action resulting in its altered or degraded structure; therefore, most of the effects shown in in vitro experiments with the pure compound cannot be directly extrapolated to in vivo systems. Yet, this does not mean that quercetin simultaneously loses its positive impact on consumer health. Even after being metabolized it may still affect the redox balance by inducing antioxidative and detoxifying enzymes or compounds which may be involved in sustaining homeostasis.

Monitoring of alcoholic fermentation of onion juice by NIR spectroscopy: valorization of worthless onions

The valorization of vegetable byproducts is one of the main objectives of industry today. The project on which this study is based examined the potential usefulness of worthless onions (Allium cepa L. sp.) and overproduction to obtain several functional products with different applications in the food industry. Near-infrared (NIR) spectroscopy, combined with multivariate calibration, has been used to monitor the alcoholic fermentation of onion juice. Good results were obtained, revealing the suitability of NIR spectroscopy for controlling and optimizing this process in real time.