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The Vidalia Story -
How Sweet It Is

Grower Solutions Magazine
Lefroy Valley
Dec 2001

by Dr. Piet Grobler
Deputy General Manager, HYGROTECH SEED

C
ontinuing research into the health and nutritional aspects of onions has led to growing interest from consumers towards milder onions with less pungency. Consumer groups are also demanding that food should be safer and healthier. Therefore, the industry has to take a look at how they are breeding, producing and marketing onions to meet these needs. It is likely that the internal qualities of onions will become more important than the external quality. To understand the new trend, a global look into what information has become available should be taken.

Health
Two major claims are being made that organosulphur compounds in onions now induce anti- palate formation in humans. This means a lower chance of thrombosis, heart attacks, strokes and better overall health.
Alliicin, a compound found in onions and garlic has a therapeutic activity by lowering blood cholesterol. Quercitin, found in high pungency onions, is thought to reduce the incidence of certain cancers.

Taste
Onion taste is also a function of organosulphur compounds and sugars. The absorption of sulphur, total bulb sulphur and the presence of other enzymes are all factors affecting onion flavour. In turn, these factors are influenced by the growing environment and the time of consumption after harvest. Pyruvate is a compund found in onions and is an indication of the onions' pungency. Mild onions should have a pungency of 5 - 7 micromoles/ g fresh weight, or less. The carbohydrate content of onions contribute to the sugar content. Carbohydrate accumulation and synthesis is a function of photosynthesis. This is influenced by leaf area, environmental conditions and variety. It was found that all sulphur compounds, including those with beneficial health properties are broken down by heat. Cooked onions are not as healthy as fresh onions.

 

Fresh onions
Health wise, it is therefore better to eat more fresh onions with a high sulphur content. The higher the pungency, the more reluctant people are to eat it. To get people to eat more onions, higher sugars and less pungency is needed. That is, to raise the volume of sulphur intake overall, without raising the concentration in a given amount of onion. Breeding is therefore aimed at increasing the sugar content and producing an onion with suitable pungency to still have it considered mild.

The Vidalia Story
Vidalia is a town in Southern Georgia, USA and also the registered trademark of the Georgia Department of Agriculture for the sweet Vidalia onions that grow in that region. Approximately 200 growers plant Vidalia onions from September through April on 6 - 7 thousand hectares. Onions are transplanted, four rows to a flat 1.35m bed, with a spacing of 125 to 150mm within the row. The sandy soils in the region have inherently low sulphur contents, vital in producing low- pungency onions. The crop is hand lifted and stored in ambient temperatures for up to six weeks. If longer storage is required, the onions are stored in bins at temperatures of 1 C, withthe atmosphere controlled at 97% N, 2% C and 1% Oxygen, allowing up to 7 months storage. Onions have to meet strict quality and pungency levels to be marketed as Vidalia Onions, guaranteeing the longevity of the brand, where it is a household name in the US. Lefroy Valley has a range of commercial varieties, with low pungency levels to suit this growing market segment. For further information, please contact Bruno Tigani on 03 5977 3733, or your local Lefroy Valley office.
 

Nutritional Value

Serving Size - 1 medium onion (raw)
Kilojules 290
Protein 1g
Carbohydrate 16g
Total Fat 0
Saturated Fat 0

Sodium 5 m
 
 
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