36 food & drink processing
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any broad scale, processors had to bridge the gap were introduced, and machine lengths were increased to
between the common historical batch soak tank process 20 and 24 feet. These larger machines had higher
to a fully-automated continuous hydration/blanching water-to-product ratios which had a direct impact upon
method. improving product quality. They are the most common
Fifty to 75 years ago, almost all dry bean processors size machine used in modern dry bean processing lines
used a batch process employing soak tank farms. A today.
precise measure of dry beans and water were introduced Throughout the 1990s additional enhancements were
into each tank, left to soak for 8 to 24 hours, then made to the continuous blanching process, such as step
followed with a short five- to 10-minute blanch. The blanching, where incremental temperature increases
beans were hydrated from 12–15 per cent moisture were made throughout the process. Beans would be
content up to 55–58 per cent, at which point they were introduced into 145 to 165°F water at the start, with
considered to be fully hydrated. staged temperature changes to 170, 180, and finally 195
With this mostly manual-controlled process, the to 205°F.
quality of the finished product often suffered if the The gradual increases in temperature dramatically
measurements of water, dry beans and soak time were decreased the incidence of bean splitting. Those
not held within narrow parameters. processors that made the switch from batch to the
The beans were then sent off to be canned or continuous blanching method during this time quickly
otherwise packaged. The soak tank process is realised the benefits of improved product quality –
functionally the same today. specifically, consistently cooked beans which were
By the early 1970s, only about 10 per cent of dry hydrated to the same degree throughout the day.
bean processors had eliminated their tank farms, opting With improved dry bean quality, continuous
instead for processing continuously through multiple blanching systems handled increasingly higher volumes
blanchers in series. of throughput.
This method reduced the hydration process from Machines that were designed to handle 12-in of
many hours to somewhere between 30 and 60 minutes product in 23-in of water reached the point of being
depending upon the bean variety. overloaded when the beans were being run frequently
Prior to 1985, blanchers were typically 48-in in 18-in in depth.
diameter with cylinders no longer than 16 feet, which Deeper loads take longer to reach the centre of mass
were supported on centre shafts. These 48-in diameter in the machine, which necessitated longer blanch times,
cylinders were a source of product damage and and in turn overcooked the beans on the outside of the
inconsistent process results. These factors were a major mass. Deeper loads can also cause the top of the
reason for poor quality. Shafts in dry bean blanchers also relatively static load to ride out of the water, causing
routinely failed from being overloaded. those beans to be under-cooked.
In the mid-1980s, 60-in and 72-in diameter machines Two subsequent major developments ensured more
uniform processes and allowed blanchers to
handle even higher throughput.
One was a gentle mechanical stirring
action that was imparted to the beans as they
progressed through the machine. The other
was a system called Hydro-Flow which was
perfected in the early 2000s. This system
applied a combination of air and water
injection which physically and buoyantly
supported the heavier loads, and more
evenly distributed the bean loading across
the width of the machine.
The system also minimised bean contact
with the auger’s perforated skin sheets,
which further reduced damage. In handling
one particular Red Kidney bean variety, for
example, damage to the fragile skin was
diminished by more than 30 per cent.
Effectively, improvements designed into
dry bean continuous blanchers, including
the Hydro-Flow system, over the past 30
years have proven successful in limiting bean
Fig. 1. The Hydro-Flow applies a combination of air and water injection which physi- damage to under five.
cally and buoyantly supports heavier loads. There are different designs of continuous
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