Agriculture Reference
In-Depth Information
Table
Cultivar differences in days to maturity, sugar and acid content and fruit
firmness in South Africa
Days to maturity from blossoming to harvest, total soluble solids (TSS) as a
refractometer measurement of the juice (%), titratable acid per g of juice,
and firmness, measured with an . mm diameter penetrometer, of apples
harvested at the optimum maturity stage.
.
Days from full
TSS
Titratable acid
Firmness
Cultivar
bloom to harvest
(%)
(g/ g)
(kg)
'Gala'/'Royal Gala'
.
.
.
'Golden Delicious'
.
.
.
'Starking'
.
.
.
'Topred'
.
.
.
'Starkrimson'
.
.
.
'Granny Smith'
.
.
.
Data from van der Merwe ( a). Reproduced with permission.
shows the range of soluble solids (sugars) and acid in four important cultivars,
harvested at the optimum stage of maturity for the maintenance of acceptable
market quality under controlled atmosphere or normal refrigerated storage.
The very high acidity of 'Granny Smith' and low acidity of 'Delicious' contrast
with each other and with the higher sugar levels and intermediate acidity of
'Golden Delicious' and 'Gala'. Some consumers prefer a sweet apple while
others prefer a more tart taste (Shewfelt,
). Flavour is discussed in detail
in Chapter
.
There are also differences in preference for apples of different sizes which
are so great as to influence choice of cultivar. Different cultivars have fruits of
different average size and weight, i.e. have different mean and modal values for
their fruit size, with a normal distribution of smaller and larger fruits around
the mean values. It is possible, indeed it is standard practice, to modify the size
distribution by choice of rootstock, pruning and fruit thinning, but it is easier
to obtain consistently large fruits of good storage quality from a naturally
large-fruited cultivar than from an intrinsically smaller fruited cultivar. In
general the production of small apples is not profitable but whereas the English
prefer medium-sized apples the Dutch prefer large ones (Combrink and Von
Mollendorff,
shows cultivar differences in fruit size, and sugars
and acids, in Germany. Japanese preference for very large apples, weighing
). Table
.
g or more per apple, can best be met by cultivars like 'Fuji' which can
be stored for more than
months in cold storage without developing flesh
browning or mealiness even if over
g (Fukuda,
). In contrast the
average fruit weight of 'Cox's Orange Pippin' is around
g with a range of
-
g (Gotz and Silbereisen,
).
