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Active-Italia: Hydroxytyrosol: Health Benefits and Use as Functional Ingredient in Meat

Hydroxytyrosol: Health Benefits and Use as Functional Ingredient in Meat

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Hydroxytyrosol (HXT) is a phenolic compound drawn from the olive tree and its leaves as a by-product obtained from the manufacturing of olive oil. It is considered the most powerful antioxidant compound after gallic acid and one of the most powerful antioxidant compounds between phenolic compounds from olive tree followed by oleuropein, caffeic and tyrosol.

Its regular consumption has several beneficial effects such as antioxidant, anti-inflammatory, anticancer, and as a protector of skin and eyes, etc. For these reasons, the use of HXT extract is a good strategy for use in meat products to replace synthetics additives.

Meat and meat product consumption provides high-quality proteins (20–25%), minerals (Fe- heme, Mg, K, Zn and Se) and vitamins (A, thiamine, riboflavin, niacin, retinol, B6, folic acid, B12, D and K) necessary for a balanced diet.

However, these products usually are rich in saturated fatty acids, and recently, the International Agency for Research on Cancer (IARC) under the World Health Organization (WHO) has classified processed meat as a carcinogen (Group I) and red meat as possible carcinogen (Group 2A) (October 2015).

In fact, carcinogenic compounds in meat could be added during their processing (synthetic additives), but they also can be formed during their storage through lipid and protein oxidation, or during cooking through the Maillard reaction.

In this way, synthetic additives such as sulphites, BHT (butylated hydroxytoluene) and BHA (butylated hydroxyanisole) are added in meat product formulation to preserve them. The use of these synthetic additives has given rise to social concern by consumers, due to studies that correlates their consumption with disease development (asthma, hyperactivity, cancer, etc.). On the other hand, lipid peroxidation in meat and meat products happens through the radical chain reaction mechanism, although oxygen presence accelerates this process. This oxidation is due to several factors such as polyunsaturated fatty acids concentration (PUFA), the deficit of antioxidants in animal feed (tocopherol, rosmarinic acid) and a high concentration of prooxidants, free radicals or added salt (NaCl). At the same time, these reactions produce reactive oxygen species (ROS) like hydroxyl radical, superoxide anion, ferryl and perferryl species, lipid peroxyl radical and secondary products like reactive carbonyl species (MDA (malondialdehyde) and 4-HNE (4-hydroxynonenal)) responsible for the rancid flavour in aged meat.

Although protein oxidation has received less attention, it has a huge influence on quality of meat. Protein oxidation has been defined as a covalent modification of protein induced either directly by reactive species or secondary products of oxidative stress.

The same oxidants that induce the lipid peroxidation produce this alteration, and carbonyl formation is a common reaction in protein oxidation.

Furthermore, proteins can react with secondary products of lipid peroxidation like aldehydes and ketones to produce complexes between proteins, proteins and carbonyls or proteins and lipids. In muscle fibres, hydroxyl radical (OH) in presence of Fe or Cu or ROS causes modifications of amino acids, like methionine, lysine, arginine, histidine, tryptophan, valine, serine and proline.

This reaction increases proteolytic enzymes and protein polymerization, which produces soluble aggregates, that promotes gelation and emulsification that modifies the texture and toughens the meat. But this not only is critical for organoleptic quality, but it might have an impact on human health and safety. For example, during cooking it increases free radical generation while it decreases the antioxidant compounds in meat, which contribute to protein oxidation.

Therefore, natural antioxidants can prevent lipid peroxidation on different ways: preventing chain inhibition by scavenging initiating radicals, breaking chain reaction, decomposing peroxides, decreasing localized oxygen concentrations and binding chain initiating catalyst such as metal ions. Therefore, the use of natural preservatives to keep the shelf life of meat has exhibited similar antioxidant properties compared to some synthetic additives. For this reason, it is a promising tool due to many fruits (grapes, grape seed, pomegranate, date, kinnow mandarin), vegetables (broccoli, potato, drumstick, pumpkin), herbs (olive leaf, acerola, grape seed, cocoa, green coffee, Ginkgo biloba, etc.) and spices (rosemary, green tea, black pepper, garlic, oregano, cinnamon, sage, thyme, mint, ginger, clove) reported antioxidant properties in meat products.

One of most potent natural antioxidant extracts is hydroxytyrosol (or 4-(2-dihydroxyphenyl)ethanol) (HXT)), just below gallic acid.

This compound is ten times more antioxidant than green tea and two times more than coenzyme Q10, additionally HXT scavenging ability is comparable to oleorupein and catechol. HXT is a phenylethanoid with demonstrated antioxidant properties in vitro, it is found in olive leaf and oil from this fruit, responsible for intense flavour and aroma, being oleuropein precursor. In addition, it has demonstrated this capacity in vivo in several studies in rats, such as Merra et al. or Lemonakis et al. , that showed the power of HXT to reduce the risk to suffer metabolic syndrome. In its chemical structure, this compound has an additional OH group in its benzene ring, compared to the tyrosol (TYR).

Therefore, it obtains a greater function as a free radical scavenging, increasing its antioxidant power, as well as its efficacy under stress conditions.
In this way, this extract has previously demonstrated its antioxidant capacity in meat products rich in unsaturated fatty acids like sausages and frankfurters with added HXT, nuts and extra virgin olive oil.

Moreover, HXT is an antioxidant compound linked to certain minerals, such as gluconate Fe (II) in black olives, which catalyzes the oxidation of this compound, so it is possible that HXT influence on biological bioavailability of some minerals and trace elements.

The objective of this paper is to review the latest literature about HXT consumption benefits, its extraction from olive leave and other sources and its used as natural antioxidant in meat and meat products as substitute of synthetics additives, with emphasis on new trends and future perspectives in investigation and meat industry.

Source of the Article

Lorena Martínez, Gaspar Ros, and Gema Nieto


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