How Sweet It Is
Grower Solutions Magazine
by Dr. Piet Grobler
Deputy General Manager, HYGROTECH SEED
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
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.
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 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.
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.
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 1º 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.
Serving Size - 1 medium onion (raw)
Total Fat 0
Sodium 5 m