There are some very intrinsic and crucial factors that govern a specific wine’s quality. They are:

factors affecting wine quality


Grape is primarily a temperate zone plant but can grow in semi-tropical conditions. The climatic conditions and the temperature must be good enough to allow the grape plant to grow healthily until fruition. Temperature of less than -7⁰ C is not suitable for wine grape production. Hill sides and slopes are preferred over plains as the sun rays are stronger if they fall at an angle as compared to that on a flat surface. Also, due to the slant, the soil doesn’t retain a lot of moisture as the water trickles down.

“One of the best ways to see how these factors impact wine is with a wine tour. A Wine tour in Spain can offer a good understanding on how location, topography or local grapes interact”.


The soil is the foundation to any crop and therefore, it applies to wine grape production too. Its composition governs the minerality, temperature, root penetration, water retention and nutrition. The soil that is good enough to retain heat and water (not a lot) is ideal for grapes. Ideal soil composition should comprise of calcium, iron, magnesium, nitrogen, phosphates and potassium. Some of the vineyard soil types are: limestone, alluvial, clay and volcanic.


Grape species differ from each other in terms of color, size and shape. However, a good wine grape has a balanced juice composition, aroma and flavor. The ripening time, disease resistance, climatic conditions and soil composition are few deciding factors for a good harvest.


Climate strongly influences the fruit. The perfect season is summer. The prolonged heat and warmth enables the fruit to evenly ripen and maintain its acid to sugar level balance. Sunlight is very significant to the grapes, so much so that its variation leads to different types of grapes. Lack of sunshine, hail, frost and heavy mists ruin the crop.

The average temperature for a good harvest must be from 10⁰ C to 20⁰ C. Humidity from 60% to 80% is ideal; more than that results in crop diseases.

Rainfall of 27 inches (approximately) all year round is desired. However, it is good for the crop maturing time. Rains during the harvest attract fungal diseases, rot and mildew.


These range from adverse conditions to different types of diseases. A few of them are:

  • Oidium – a kind of fungal spore that causes mildew
  • Frost
  • Hail
  • Powdery Mildew -A type of fungal disease. It leaves a dusty, powdery coating on the grape.
  • Downy Mildew – A variant of powdery mildew. It leaves a fuzzy deposit on the grape.
  • Phylloxera – A type of louse that starts an epidemic (plague) in grapevines.
  • Plant Virus
  • Millerandage – Grapes differing remarkably in size and maturity in a bunch. It happens due to extreme cold weather.
  • Coulure – Grapes fail to develop after flowering.
  • Botrytis cinerea – A type of fungus, also known as grey mould.

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