Annona Species Monograph.pdf - Crops for the Future

Chapter 7. Uses
(RH), before finally being weighed and washed with 0.5% potassium sorbic
acid. Fusagri (1982) demonstrated that 12.5°C is the best temperature to
mature and store soursop fruits; at this temperature the fruits are preserved
for up to 5 days. After maturation, the fruits are selected again, peeled and
the pulp separated mechanically.
Pulp can be pasteurised at 85°C and nectar at 90.6°C. Both can then be stored
in cans for a year at 29.4°C (Bueso, 1980). More recently, Umme et al.
(1997) established that the best conditions for pasteurisation of soursop pulp
are a pulp : water mixture of 2:1, 78.8°C for 69 s at pH 3.7. Under these
conditions, the inactivation of pectinesterase enzymatic activity is maximized
and ascorbic acid is preserved, which helps to maintain quality.
Frozen soursop puree can be stored for 400 days at -23°C (Bueso, 1980). To
prepare this puree, the sugar content should be adjusted to 45-59°Brix; with
45°Brix, ascorbic acid retention is higher in the pasteurised puree. Ascorbic
acid should be added to the pasteurised puree at a rate of 0.5-1.5 g/0.45 kg;
this improves the retention of the nectar's flavour and serves as an antioxidant
to control polyphenol oxidase-mediated pulp darkening of the fruit
juices (De Oliveira et al., 1994). The sweetened or unsweetened frozen
nectar can be preserved by pasteurisation. Unsweetened nectar can be
pasteurised at a temperature of 90.6°C, while higher temperatures give
inferior final products. The same is observed for sweetened nectars. While
higher temperatures reduce pectinesterase activity they also increase ascorbic
acid retention.
Another industrial application involves the extraction of essential oils present
in soursop pulp. These oils, such as esters of aliphatic acids, have potential to
improve the flavour of processed fruit products (Jirovetz et al., 1998).
Sugar apple pulp can also be processed and frozen. Its industrial processing
is less important than that of cherimoya and soursop, but it is used to prepare
drinks, fermented liquors and ice creams (Prasada and Rao, 1984). For this
purpose, the fruits should be peeled and cut by hand, and the seeds extracted
from the pulp. The pulp is heated for 3 min at 70°C, stored in jars and then
double boiled for 15 min at 95°C. Sealed jars can be stored at 27°C for 150
days, during which time the acidity and total reducing sugar concentrations
increase and ascorbic acid content decreases. A similar study was done on
the nectar prepared with acclimatised (in an ethylene chamber at 16°C and
RH 80%) and non-climatized (at room temperature for 72 h) fruits. Before
the pasteurisation process, the pulp was adjusted with water, sugar and citric
acid (pulp 1 kg, water 2.51 kg, sugar 0.37 kg and citric acid 1 g) (Leal, 1990).
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