Olive oil and phenolic compounds

Phenolic compounds are often described as effective antioxidants. These compounds have a great importance for several characteristics of the olive oil, such as flavor, shelf-life and resistance against oxidation.

The class of phenols present in olive oils encompasses a large number of different substances such as vanillic acid, caffeic acid, hydroxytyrosol, tyrosol, oleuropein, ligstroside, gallic acid, coumaric acid and flavonoids.

In olive oils the bitter taste is due to phenolic compounds and cinnamic acid, while the pungency is due to oleuropein.

The amount of phenolic compounds in olive oils cultivars varies from 150 to 700 ppm and is affected by various factors such as cultivar, degree of maturation, climatic conditions and pest damage to fruit. Green olives oil in phenolic content and with a more aromatic and fruity flavor.

Oleuropein is the major phenolic in olive fruits. Oleuropein underwent significant changes in its concentration during fruit development.

Oleuropein has been shown to be responsible for the high resistance, robustness and good immune function of the olive tree. In it original, unaltered form, this substance lowers, blood pressure, dilates blood vessels, and protects against heart rhythm disturbances.

Olive oil and phenolic compounds

Natural antioxidants

Antioxidants have been described as “substance that, when present at low concentrations compared with those of an oxidizable substrate, significantly retards oxidation of that substrate”.

The antioxidants may be classed as natural and synthetic. Many fats and oils, particularly in the unrefined form, are quite stable to oxidative rancidity because they contain natural antioxidants.

It has generally been shown that antioxidants compounds from plants are phenolic in nature and encompass such groups of compounds as tocopherols, carotenoids, phenolic acids, flavonoids and diterpenes. The tocopherols (α, β and γ) are the most important of the natural antioxidants and are widespread in both plant and animal tissues.

α- tocopherols

Natural antioxidants, mostly absorb light in the UV region (100-400 nm), can effectively scavenge free radicals, and chelate transition metals, thus stopping progressive autoxidative damage and production of off-odors and off-tastes in food products.
Natural antioxidants

Phenolic in raspberry

The wide range of values reported for various classes of phenolic in berries reflect differences in genetics, cultural practices, environmental growing conditions, and possibly maturation. It was reported that the color of raspberry juice correlated with the total phenolic.

Black raspberries had the highest ORAC (Oxygen Radical Absorbance), anthocyanin and phenolic compounds. Anthocyanins are the major phenolics present in black raspberries, with levels ranging from 464 to 627 mg/100 g FW.

Black raspberries also contain appreciable levels of total ellagic acid which most likely is due to high concentrations of ellagitannins in the fruit.

Red raspberry seeds contained more phenolic compounds (ellagic acid content) than pulp, but leaves had a higher content than seeds or pulp. Phenolic compounds ellagic acid, a dimeric derivative of gallic acid, is suggested as an anti- carcinogenic/anti-mutagenic compound. It is present in plants in the form of hydrolysable tannins called ellagitannins.

Only red raspberries had detectable amounts of procyanidin oligomers (monomer, dimers and trimers).
Phenolic in raspberry

Quercetin in food

Several hundred flavones and flavonol aglycones are known, but only three are common: kaempferol, quercetin, and myricetin.

Quercetin has the widest distribution in nature of phenolic compounds, and 135 different glycosides of quercetin.

It is the potent flavonoid and antioxidant found naturally in the pulp of many citrus fruits and in apple skins, buckwheat, red onions, red grapes, wine, and tea. Quercetin also found in onions, cayenne pepper, and garlic.

It is estimated that the average adult diet provides up to 50 mg of quercetin each day.

Evidence indicates that quercetin has antiviral activity, both in vivo and in vitro, most markedly against herpes simplex type I, para-influenza types 3, polio virus type I, and respiratory syncytial virus.

In cardiovascular system, it prevents free radicals from oxidizing low-density lipoproteins (LDL). If LDL becomes oxidized, it will be precursor to arterial damage and atherosclerosis.

However, hypersensitive individuals may experience headaches or tingling. While rare, other reported side effects include gastrointestinal discomfort, hematoma, and kidney toxicity.
Quercetin in food

Classification of Lipids

Classification of Lipids
Lipids include all substances that are extractable from biological materials with the usual fat solvents (ether, chloroform, benzene, carbon tetrachloride, acetone, etc). Certain lipids are an energy source for the cell, others are structural compounds (particularly important are the lipid constituents of cell and organelle membranes), and still other function as hormones. This diversity of function recalls the not too remote past when lipids were considered to be inert constituents of adipose cells.

Of the many compounds classified as lipids, only fraction is significant in the diet, or in the structure and function of the human cell. The following classification is limited to lipids of importance in animal nutrition and excludes the fat soluble vitamins that, although properly classified as lipids, following the classic practice of nutritionist.

A. Simple Lipids
Fatty acids
Neutral fats (mono-, di- and triacyl glycerols)
Wax
*Sterol ester
*Nonsterol ester

B. Compound Lipids
Phospholipids
*Phosphatidic acids, lecithin, cephalins, etc
*Plasmalogens
*Sphinghomyelins
Glycolipid (carbohydrate containing)
Lipoproteins (lipids in combination with protein)

C. Derived Lipids, alcohol (including sterols and hydrocarbons)
Classification of Lipids