Chemistry Reference
In-Depth Information
screw press to get a 9-10
◦
brix cloudy green juice. The juice is centrifuged to reduce green
solid particles to below 5% and pasteurized. Pasteurization results in protein flocculation
and juice is then cooled for clarification by static decantation. The resulting juice can be
concentrated or used as canning syrup after fining, classic filtration and decantation. The
systematic use of ultrafiltration is possible when using enzymatic treatments at the clarifica-
tion stage after cooling to 50
◦
C for several hours. Enzymes like Peclyve Pineapple (Lyven),
Rohapect B1L (ABEnzymes) or Rapidase Pineapple (DSM) are used to process pineapple
mill juice concentrate. The presence of natural gum in pineapple juice has been found to
decrease ultrafiltration capabilities, to increase pulp suspension and foaming properties of
the juice. This gum is a neutral polysaccharide containing 70% sugars that are predominantly
galactomannans (2.25 mannose:1 galactose).
25
Because of this gum, the ultrafiltration flux
rate quickly drops, becoming a bottleneck in the process (cut-off 10 000 Dalton). Enzymes
improve the ultrafiltration flux rate since they contain the right hemicellulases to hydrolyze
the gum. Juice viscosity is decreased, making it easier to clarify and concentrate at 62
◦
brix for use as a cover syrup or a fruit sugar source after deionization of colour and aroma
removal.
11.5.4 Citrus processing
Combined citrus production in Brazil, USA, China, Mexico and Spain was estimated at 72.8
mmt in 2006, of which 47.1 mmt were oranges, 15 mmt tangerines, 4.3 mmt lemons and
4 mmt grapefruits. That year Brazil produced the most oranges (18.2 mmt), followed by the
USA (10.6 mmt), China (4.45 mmt) and Spain (2.7 mmt).
26
Global orange juice concentrate
production in 2006 reached 2.3 mmt (at 65
◦
brix). Europe imported 1.4 mmt of orange juice
concentrate that year (excluding products from non-concentrate juice), and 92 840 tonnes of
grapefruit juice concentrate. Argentina is the world's leading lemon producing country. It
exported 46 347 tonnes of lemon juice in 2006.
4
A schematic diagram of orange processing
is shown in Fig. 11.9 from Goodrich and Braddock.
27
Citrus juice processing gives rise to
numerous by-products, of which pectin and essential oils are the most important.
There are several reasons why commercial pectinases are not used for premium juice
processing. Their use is not permitted in certain countries, and classic pectinases containing
pectinmethylesterase activity clarify the juice. Enzymes are therefore only used to process
by-products. The key applications are described below.
11.5.4.1
Pulp washing
Expressed juice from extractors contains pulp and cell membrane residue. This is filtered
out when the juice is run through a finisher to reduce pulp content to about 12%. The
excess pulp and tissue by-products leaving the primary finishers are then put through a
pulp wash system. The pulp wash system comprises a series of secondary finishers with
multi-stage counter current washing systems. Around 5-7% of soluble solids are recovered,
with a high pectin content. Pectinases Rohapect PTE (ABEnzymes), Citrozym (Novozymes)
or Rapidase C80KPO or Rapidase Citrus cloudy (DSM) are added at ambient temperature
for viscosity reduction, inducing recovery of sugars and soluble solids with high yield.
The pulp wash product can be concentrated at 65
◦
brix. This product can be added to
sodas as a natural source of cloudiness. In this process, it is important to control and
limit pectin degradation to reduce viscosity without destabilizing the particles that give
