RESUMEN
Dairy beverages containing emulsified linseed oil is a suitable vehicle for delivering polyunsaturated fatty acids to consumers. However, these beverages are prone to oxidation. The purpose of this study was to evaluate the effect of adding various concentrations (0, 0.001, 0.01 and 0.1% (w/w)) of green tea extract (GTE) to dairy beverages (DB) containing linseed oil (2.0%, w/w), in order to inhibit lipid oxidation during storage at high temperature (50 °C) or under fluorescent light exposure. During storage, the concentration of catechin (C), epicatechin (EC) and epicatechin gallate (ECG) were significantly reduced (P ≤ 0.05) and degradation rate was greater when the DB were exposed to light (C 35%, EC 74% and ECG 68%) as compared to high temperature (C 34%, EC 45% and ECG 49%). In DB without GTE, the conjugated dienes (CD) hydroperoxides concentration increased significantly (P ≤ 0.05) from 23 mmol kg-1 fat to 243 mmol kg-1 fat under 6-day-light exposition, and to 83 mmol kg-1 fat under 6-day-heat temperature. The addition of GTE significantly increased the antioxidant capacity of DB and reduced the formation of CD, propanal and hexanal, induced by light exposure or high temperature. GTE at 0.10% completely inhibited CD formation during the storage period and reduced propanal and hexanal concentrations below the threshold.
Asunto(s)
Catequina , Bebidas , Aceite de Linaza , Extractos Vegetales , TéRESUMEN
Grape extracts can be added to milk to produce cheese with a high concentration of polyphenols. Four commercial extracts from whole grape, grape seed, and grape skin (2 extracts) were characterized and added to milk at concentrations of 0, 0.1, 0.2, and 0.3% (wt/vol). The effect of grape extracts on the kinetics of milk clotting, milk gel texture, and syneresis were determined, and model cheeses were produced. Whole grape and grape seed extracts contained a similar concentration of polyphenolic compounds and about twice the amount found in grape skin extracts. Radical scavenging activity was directly proportional to the phenolic compounds content. When added to milk, grape extracts increased rennet-induced clotting time and decreased the clotting rate. Although differences were observed between the extracts, the concentration added to milk was the main factor influencing clotting properties. With increasing concentrations of grape extracts, milk gels showed increased brittleness and reduced firmness. In addition, syneresis of milk gels decreased with increasing concentrations of grape extracts, which resulted in cheeses with a higher moisture content. The presence of grape extracts in milk slightly increased protein recovery in cheese but had no effect on fat recovery. With whole grape or grape seed extracts added to milk at 0.1% (wt/vol), the recovery coefficient for polyphenols was about 0.63, and decreased with increasing extract concentration in milk. Better polyphenol recovery was observed for grape seed extracts (0.87), with no concentration effect. Commercial extracts from whole grape, grape seed, or grape skin can be added to milk in the 0.1 to 0.3% (wt/vol) concentration range to produce cheese with potential health benefits, without a negative effect on cheese yield.
Asunto(s)
Queso/análisis , Manipulación de Alimentos/métodos , Leche/química , Extractos Vegetales/química , Vitis/química , Animales , Quimosina/química , Geles/química , Concentración de Iones de Hidrógeno , Proteínas de la Leche/química , Polifenoles/químicaRESUMEN
Nutritional value is a priority in new product development. Using vegetable or marine oils, rich in polyunsaturated fatty acids, in dairy beverage formulations is an option to provide the consumers with healthier products. However, these formulations are prone to oxidation, which is responsible for rapid flavour degradation and the development of potentially toxic reaction products during storage. Flaxseed lignans, secoisolariciresinol diglucoside (SDG), and its mammalian metabolites have antioxidant activity and could be used in beverage formulations to prevent oxidation. Commercially available SDG extract was added to the formulation of dairy beverages enriched with flaxseed oil. As an alternative approach, dairy beverages were produced from milk naturally rich in SDG metabolites obtained through the alteration of cow diet. Resistance to oxidation was determined from the kinetics of hexanal and propanal production during heat and light exposure treatments. Increasing SDG concentration in dairy beverage slightly reduced redox potential but had no effect on oxygen consumption during oxidation treatments. The presence of SDG in dairy beverage significantly improved resistance to heat- and light-induced oxidation. However, purified enterolactone, a mammalian metabolite from SDG, prevented oxidation at much lower concentrations. The use of milk from dairy cow fed flaxseed meal did not improve resistance to oxidation in dairy beverage. Enterolactone concentration in milk was increased by the experimental diet but it remained too low to observe any significant effect on dairy beverage oxidation.