Many studies have proved that bioactive components of Aloe vera have an anti-inflammatory effect and support lipid and carbohydrate metabolism, helping to maintain normal sugar and cholesterol levels in blood and normal body weight. When aloe is applied externally, it accelerates the regeneration of the damaged skin. Aloe contains antioxidants, which may increase the shelf-life and nutritional value of food; therefore, it is widely used in cosmetic, pharmaceutical and food industry. An antioxidant activity was shown for leaf’s skin, flowers and gel of aloe. In this work the future of A. vera as effective antioxidants is primarily discussed and expected trends are summarised. Furthermore, the bioactive components and the health-promoting effects of A. vera are investigated.

The present study examined the antioxidative activity of water and ethanol extracts of green and black tea leaves against the oxidation of heated sunflower oil and lard. Oxidation was conducted at 110 °C in the Rancimat test. Total polyphenols and catechin contents in tea extracts were measured. The research showed that the total polyphenol content in green and black tea leaves was 205.2 and 148.7 mg/g, respectively. In tea leaves extracts, it ranged between 245.9 mg/g and 837.7 mg/g and depended on the extraction solvent and the kind of tea used (p <0.001). The highest polyphenol content was observed in samples extracted with 95% ethanol, lower contents were found with the use of water. Results showed that the highest antioxidant activity, measured as an induction period, with 1000 ppm green tea ethanol extract, was comparable to á‐tocopherol activity in sunflower oil. In lard, the longest induction period was measured with 500 and 1000 ppm of green tea ethanol extract. Other tea extract concentrations were significantly less active. Statistical analysis of the tea extract antioxidant activity in lipids in the Rancimat test showed an essential influence of the catechin contents. Further statistical analysis also showed an influence of (−)‐epicatechin gallate (ECG), (−)‐epicatechin (EC), and (+)‐catechin (C) contents in the tea extracts on the antioxidant activity in lipids. It was stated that the antioxidant activity was higher in tea extracts containing high levels of ECG, EC, and C.

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This study investigated the effect of antioxidants on lipid stability and changes in protein nutritional value of frozen-stored meat products. The extracts from thyme, green tea, rosemary were used to enrich fried meatballs from ground pork. During 180-day storage of meat products, the lipid oxidation (peroxide and TBARS value), methionine and lysine availability and protein digestibility were periodically monitored. The results were compared with BHT. The addition of extracts limited lipid oxidation in stored meatballs. The extracts from tea were superior to the others from thyme and rosemary. Moreover, the extracts reduced changes in amino acids content, as well as protein digestibility, during storage time. The highest ability to lower the losses in the nutritional value of proteins was demonstrated for rosemary extract. These results indicate that plant extracts can be utilized to prolong shelf-life of the products by protecting them against lipid oxidation and deterioration of their nutritional quality.

This study presents several aspects of the mutual interaction between lipids and proteins. Nutritional and technological implications of the reaction of oxidized lipids with proteins are discussed. Changes are highlighted in the content of amino acids and protein digestibility, formation of cross--links, fl avor compounds, as well as the formation of colored non-enzymatic browning products. Attention is paid to the agents which may determine the reaction of amino acids with the products of lipid oxidation, i.e. the presence of catalysts or inhibitors in the environment, the presence of water, pH of the environment, temperature or reaction time. It was also noted that the conformation of the protein structure, the surface charge, the affi nity, and the accessibility of reactive groups affect the intensity of these interactions. This review article presents methods which reduce oxidative rancidity due to the use of antioxidant compounds, particularly the possibility of the use of natural antioxidants that reduce the number of lipid and protein oxidation products, and are simultaneously able to model the nutritional value of food.

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The total polyphenol content and antioxidant activity of ethanol herb extract in different lipid systems was determined. For the purpose of this study, five representatives of spices were selected: garlic (Allium sativum L.), marjoram (Origanum majorana L.), peppermint (Mentha piperita L.), rosemary (Rosmarinus officinalis L.) and thyme (Thymus vulgaris L.). Lipid analyses showed different antioxidant potential of herbs extracts depending on the system used. Rancimat and Oxidograph tests showed that extract antioxidant potential in lard was higher than in sunflower oil. Thyme and marjoram extract exhibited the highest antioxidant activity but the lowest was recorded for garlic and mint one. Statistical Analysis showed a high correlation between total polyphenol content and antioxidant activity. Lipid oxidative stability in the Schaal oven test showed different trends, however, highest activity was observed in the samples of thyme and rosemary extract. Mint extract in sunflower oil and lard on cellulose matrix exhibited prooxidative activity.