Grape-seed oil

Grape-seed oil is a plant-based oil obtained from the seeds of grapes and is therefore an abundant by-product of the wine-making process. Given its high percentage of linoleic acid (omega-6 fatty acids), it is thought to be particularly harmful to health.

Culinary uses:

Grape-seed oil comes in two varieties: cold-pressed (unrefined) and refined. The latter is obtained after a multistage refining process at temperatures exceeding 212 °F. Refined grape-seed oil has a neutral color and taste.¹ With a high smoke point of 420 °F, refined grape-seed oil stands up well to heat and is therefore suitable for stir-frying and sautéing.² However, the refining process results in the loss of valuable unsaturated fatty acids, secondary plant substances, and proteins.³ In addition, unsaturated fatty acids are converted into trans fats.

Cold-pressed virgin grape-seed oil is aromatic, unrefined, and light yellowish-green in color. Slightly nutty in flavor, its taste varies depending on the variety of grape used. Cold-pressed or expeller-pressed oils are perfect for seasoning salads, sauces, or accompanying cheeses, that is, for recipes in which the oil does not need to be heated. This plant-based oil also has a relatively high smoke point.²

Despite its versatility, grape-seed oil contains high levels of linoleic acid (LA), and we therefore recommend substituting it with canola oil, which has significantly lower levels of this fatty acid.

Purchasing — where to shop:

Cold-pressed grape-seed oil can be in found in health stores or online

Storage:

In general, cold-pressed oils have a shorter shelf life than refined oils. Since grape-seed oil contains a high percentage of unsaturated fatty acids, it shouldn’t be exposed to air, light, or heat. Grape-seed oil is also a rich source of vitamin A, making it resistant to oxidation; this is why it doesn’t turn rancid quickly. As a result, grape-seed oil has a longer shelf life than other common oils and can be kept for up to 18 months without going bad. Grape-seed oil should be kept in a tightly closed container in a cool, dark location. You should avoid storing it in the refrigerator.⁴

Ingredients:

Grape-seed oil is a rich source of vitamin E and essential fatty acids. Unfortunately, only a minimal amount of these are omega-3 fatty acids, as approximately 69 % of the essential fatty acids found in grape-seed oil are linoleic acid, an omega-6 fatty acid. Excessive consumption of omega-6 promotes inflammation and can increase the risk of stroke if there is an imbalance in the ratio of omega-3 to omega-6 fatty acids in the diet. As grape-seed oil is so high in linoleic acid and low in alpha-linolenic acids, this imbalance is notably high.⁵

Health aspects:

Thanks to the high levels of vitamin E and procyanidin⁶ found in grape-seed oil, it is a rich source of antioxidants.¹² This reduces cell damage and atherosclerosis. Furthermore, its antioxidant properties make grape-seed oil renowned for its anti-inflammatory, anticancer,¹¹ antimicrobial, and neuroprotective effects.⁷ To this end, grape-seed oil reduces cholesterol levels, aids with metabolic disorders, and is very effective in the treatment of dermatological conditions such as eczema, acne, and psoriasis. In addition, the lecithin in grape-seed oil improves brain function and has a positive impact on blood count.⁶

Linoleic acid plays many important roles in our body, but it is important to consume it in moderation and make sure the LA:ALA ratio is correct. This is achieved by consuming foods rich in alpha-linolenic acid (ALA) of natural origin as opposed to linoleic acid (LA).

Dangers/intolerances:

Given the high temperatures grape-seed oil undergoes during the refining process, 3-MCPD and glycidol esters form; these are processing contaminants found in a wide range of vegetable oils.³ For this reason, it’s best to avoid buying refined grape-seed oil.

At the beginning of the 1980s, grape-seed oil made the headlines because of the discovery of high levels of polycyclic aromatic hydrocarbons in some grape-seed oil samples. These were most likely caused by gases that formed when the seeds were dried.¹

Uses as a medicinal plant:

Grape-seed extract (OCP, oligomeric proanthocyanidins) is obtained from the husks of crushed grape seeds. It is highly regarded for its antioxidant properties and is available to buy as a supplement in liquid or capsule form. It is thought to be effective in the protection against bowel, stomach, breast, and prostate cancers. The extract can help protect against liver damage caused by chemotherapy as well as help prevent cardiovascular disease.

Scientific studies carried out in India found that grape-seed extract had similar effects on diabetes as the pharmaceutical drug "Metfo....", which is commonly used to treat the disease. Grape-seed extract is also believed to stabilize "insulin levels".

Among many other positive effects, grape seed extract is also thought to help reduce hair loss as it promotes blood circulation in the scalp.⁹

However, as most studies on grape-seed extract have been conducted with only a small number of test subjects, there is considerable doubt cast on the scientific validity of this research and its conclusive effects.¹⁰

When taking grape-seed extract, avoid consuming dairy products at the same time as the milk proteins reduce the antioxidant effects the extract has on the body.¹³

Origin:

The common grapevine (Vitis vinifera) is cultivated all over the world for the production of grapes. Grapevines are grown in vineyards, gardens, walls, and buildings, but mainly in dry and sunny soils, even on plains or at very high altitudes (including the Himalayas). As an ancestor of ancient crops, grapevines can be found in flood plains, river banks, forest margins, ravines, and in shrubbery.

The Eurasian wild grapevine (Vitis sylvestris) is an endangered plant in Central Europe. On the contrary, this variety is found widespread throughout the Mediterranean region, in central France, southwest Switzerland, the upper Rhine lowlands, in the basins of the Danube river, in southern Russia, and Asia Minor (Anatolia).

General information:

Overall, grape seeds contain between 8–20 % oil (when dry), with Bordeaux grapes being the richest in oil.¹² While oil extraction from the seeds is primarily a by-product of the wine-making industry, grape-seed oil is found in many recipes dating back to the Middle Ages.⁶

After the seeds have been cold-pressed for oil, the leftover pomace is dried and finely ground into a powder to make grape-seed flour. This can be used in bread or noodle dishes. As grape-seed flour can withstand high temperatures, it maintains its valuable nutrients, making it a great option for baking. However, it should be used in proportion (5–10 %) to conventional flour. It gives baked foods a wonderfully earthy, hearty flavor.¹³

Occasionally, grape-seed oil is used to produce margarine.

In addition to its versatile use in cooking and nutrition, the cosmetic industry benefits from the positive impacts that the procyanidin in grape seeds has on the skin. Absorbed well without leaving a greasy residue, it is thought to give the skin elasticity as well as leave it regenerated and moisturized. For many years, phytosterols have been an important component in cosmetics because of the protective barrier they provide sensitive skin against UV rays.

Commercially, grape-seed oil is used in the production of soaps, varnishes, paints, inks, aerosols, and to a limited extent linoleum.⁶

Literature - Sources:

Author: Francisco (Paco) Villar | 28 Jun 2019