Annona Species Monograph.pdf - Crops for the Future

Chapter 11. Harvest & Processing
scalding (1 minute); 6) cooling; 7) soluble solids determination; 8) 0.1%
sodium benzoate addition; 9) blending (10 minutes); 10) sieving; 11) sugar
addition; 12) air elimination and pulp concentration (60°C); 13) deposition of
pulp into a container; 14) covering; 15) cooling; 16) labelling; 17) storage.
The fruits are hand peeled by making 3 to 4 shallow cuts in the skin and
pulling the skin sections from the apical extremity, being careful to eliminate
all the skin to avoid depreciation of pulp quality.
Since soursop hand-peeling is a very difficult process to use commercially,
Mororó et al. (1997) recommended a more practical processor (Fig. 11-1) for
pulp extraction. After primary selection of the fruits, they are rinsed by
immersion in 10 to 15 ppm chlorinated water (Fig. 11-1A), followed by
rinsing with water (Fig. 11-1B). The aim is to remove the residues on the
fruit surface, such as dust, soil and pesticides. Following further inspection
(Fig. 11-1C) any damaged or unripe fruits that could remain from the first
selection are discarded. After peeling, the fruits are transported by an endless
spiral system (Fig. 11-1D) to a 'lung container' (Fig. 11-1E). The function of
the lung container is to equilibrate pulp flux between extraction and
automatic packing, using a dosimeter pump (Fig. 11-1H). The extraction is
made by continuously sieving the fruit to separate the pulp from the seeds
and other residues. Fine extractions can be made by using a small-hole sieve
to separate the fibres, although the fibres are considered as an important
dietary component for human health. The pulp is automatically packed into
polythene bags and sealed (Fig. 11-1G).
The percentage of pulp recovery ranges from 62 to 85.5%. The variation is
due to the type of equipment, extraction method, cultivar, cultural practices
and number of seeds per fruit (Nakasone and Paull, 1998). Soursop pulp is
viscous, and its dilution produces flat and weak nectar. In addition, the lack
of uniformity in acidity and soluble solids concentration generally requires
homogenization (Torres and Sánchez, 1992). In order to obtain a good nectar,
the pH should be adjusted to 3.7 by the addition of citric acid, and the Brix to
15° by addition of sugar, thus creating an appropriate balance of acidity,
sweetness and flavour (Torres and Sánchez, 1992; Nakasone and Paull,
1998). High starch, polyphenoxidase and peroxidase contents decrease the
stability of the product's colour and taste (Torres and Sánchez, 1992). To
produce a high quality product, soursop pulp should be processed below
93°C and frozen into polythene bags (Pinto, 1991; Torres and Sánchez,
1992).
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