rexresearch.com
Jeff HASTINGS
Food Preservation
http://www.abc.net.au/news/2016-08-02/avocado-technology-food-processing-crop/7679108
Breakthrough technology to stop
processed avocados browning
By Jennifer Nichols
A Queensland company has developed world-first food technology it
believes could revolutionise the global processed avocado market.
Naturo All Natural Technologies has patented a technique to stop
avocados browning, without using chemicals or changing the
flavour.
Agricultural engineer Jeff Hastings said his company's technology
offers enormous potential to value-add to avocados, that could now
be used by fast food companies and restaurants.
"The concept came out of a group of avocado growers some three
years ago who wanted to do more with avocados, create more value
from avocados, so I got involved in looking at options," Mr
Hastings said.
"They came and left but I continued on to see if there was some
way of stopping the avocadoes going brown and eventually after a
bunch of experiments in my kitchen and playing around with
different ideas we hit on one idea that showed some promise.
"So then we went further to commercialise it and started
manufacturing machines."
Browning remains the major issue for processed avocado.
"Anything that's cut, the browning process starts and within a few
hours and you've got brown avocado which you can't eat," Mr
Hastings said.
"So if we can extend that browning process, extend that reaction,
then you would give consumers the opportunity to eat that sliced
or diced or pulped avocado over a longer period."
The retro looking 'Avocado Time Machine' can process up to 500
kilograms of avocado an hour.
The Mount Coolum-based engineer said the secret lay in the
technology's ability to switch off the enzyme responsible for the
fruit's browning by using pressure fluctuations generated by
steam.
It also eliminates crop wastage, by processing second-grade
avocados into pulp and slices.
"There's essentially two groups of technologies, high pressure
processing [HPP] is used predominately on pulp and guacamole.
"It's aimed at killing the pathogen level, the microbe level in
the avocado pulp and it does a great job of that.
"The only problem with it is, as soon as you open the HPP bag, the
browning process starts straight away.
"The second group of technology is the sliced, diced products
produced around the world in pretty much the same way and they all
use either chemicals or additives or products to treat the surface
of the avocado.
"But that imparts a flavour characteristic to the dice or slice
which is a little bit acidic and unpleasant to the taste.
"Our technology kind of takes the best of all the technologies
that are there.
"It has the bacterial kill, the food safety step, we don't change
the flavour, or taste of the avocado and most importantly it has a
shelf life of at least ten days after opening the bag."
Mr Hastings believes the technology provides opportunities for
Australian avocado growers to produce sliced, diced or pulped
product for use here and abroad.
The 'Avocado Time Machine' was not in use on the day ABC Rural
visited but Mr Hastings explained the process.
"The avocados would come off a conveyor belt where they've been
sliced, diced or pulped and then would come into our machine," he
said.
"Some six minutes later it comes out the other end.
"The magic occurs in the first part of the process, with a
combination of pressure fluctuations, temperatures. There's
nothing added, it's all just natural processes.
"It's all about finding a way of triggering or stopping the enzyme
and turning that off.
"We make a claim of ten days shelf life after you've opened the
bag so you can leave them in the fridge and keep eating them for
ten days, but they will last a lot longer than that."
Mr Hastings' business partner Frank Schreiber said the
world-patented technology had met food safety standards required
to export avocado products to fast-growing export markets
including the USA, Asia and Europe.
A Sunshine Coast avocado co-operative, that did not want to be
identified at this stage, had bought the first 'Avocado Time
Machine'.
http://www.businessnewsaus.com.au/articles/queensland-company-launches--avocado-time-machine-.html
10 June 2016
QUEENSLAND COMPANY LAUNCHES 'AVOCADO TIME
MACHINE'
THE short life span of avocados has long frustrated those who love
and devour the fruit, however, one Australian company is claiming
a major breakthrough for the world-wide avocado industry.
Queensland food technology company Naturo All Natural Technologies
has developed an all-natural processing technology which stops
browning of freshly cut avocado and prolongs shelf life for a
minimum of 10 days.
The Australian invention, Natavo Zero, uses a 100 per cent natural
process which preserves the nutritional properties and taste of
the avocado without chemicals, additives, preservatives or
processing aids.
The secret of the technology lies in the company's ability to
switch off the enzyme responsible for the fruit's browning via
pressure fluctuations generated by steam.
The safe and affordable processing solution meets all food safety
standards required to export avocado products to some of the
fastest growing overseas markets including the USA, Asia and
Europe.
Naturo's directors Frank Schreiber and Jeff Hastings spent four
years researching and developing their invention which has a
world-wide patent.
The duo says the time was right to launch their 'Avocado Time
Machine' to the world.
Hastings says the technology has the potential to become the new
industry standard.
"It is difficult for people to select, buy and enjoy the perfect
avocado because more often than not the fruit has already
deteriorated or started its browning process," says Hastings.
"Additionally, the relatively high cost of avocados, combined with
the fruit's short shelf life makes it a challenge to incorporate
the fruit into a daily diet, especially in countries which have no
access to fresh avocados. Our technology changes all that."
Meanwhile, Schreiber says the arrival of the technology opens up
new markets and new opportunities for fresh and frozen avocado
products.
"Although there is a range of avocado products currently on the
market, nearly all of them contain additives such as antioxidants,
acids and preservatives which not only alter the taste of the
fruit but do very little to stop the browning once the packaging
is opened," says Schreiber.
"We see Natavo Zero technology as a benchmark for innovation and
quality in the avocado industry and expect that the consumer's
appetite for healthier, 100 per cent natural and safe avocado
products is realised by the local industry.
"An Australian company has already secured the opportunity to be
the first processor to use the technology and we expect they will
be producing avocado products later this year."
"This is a rare win-win-win situation for everybody involved; it's
a win for avocado farmers, a win for the food industry and
ultimately a win for consumers."
The Natavo Zero technology and the 'Avocado Time Machine are
designed and manufactured in Australia. The latest model 'ATM 3.5'
has a processing capacity of 1,100lbs (500 Kg) cut avocado fruit
per hour, which is equivalent to about 4000 avocado fruit per
hour.
http://www.sciencedirect.com/science/article/pii/S0308814608008510
doi:10.1016/j.foodchem.2008.07.027
Steam blanching effect on
polyphenoloxidase, peroxidase and colour of mango (Mangifera
indica L.) slices
Cheikh Ndiaye , Shi-Ying Xu, Zhang Wang
Abstract
The heat stability of peroxidase (POD) and polyphenoloxidase (PPO)
was investigated in mango (Mangifera indica L.) slices, and the
relative colour was studied after different steam blanching times.
There was complete inactivation after 5 min for POD and 7 min for
PPO. Steam blanching of 3 min gave residual activity of 2.85% and
8.33% for PPO and POD, respectively, and when compared with
samples blanched for 5 min had no effect on colour over 20 days of
storage. Correlation was found between activities of PPO, POD and
colour change over 20 days. After 7 min steam blanching the
browning index was stable but less than at 3 and 5 min because
non-enzymic browning had occurred. This research suggests that
yellowness (b) and lightness (L) values contribute positively to
the browning index (BI), compared to redness (a).
http://link.springer.com/article/10.1007/s002170050038
Zeitschrift für Lebensmitteluntersuchung und -Forschung A,
January 1997, Volume 204, Issue 1, pp 60-65
Improvement of frozen banana (Musa
cavendishii, cv. Enana) colour by blanching: relationship
between browning, phenols and polyphenol oxidase and
peroxidase activities
M. P. Cano, Begoña de Ancos, M. Gloria Lobo, Mariana
Santos
Abstract
Browning in banana (Musa cavendishii, cv. Enana) processed
products is a result of phenol oxidation catalysed by polyphenol
oxidase (PPO) and peroxidase (POD) or of other non-enzymatic
reactions (Maillard and Strecker mechanisms). Microwave and steam
blanching significantly reduced PPO and POD activities and phenol
levels in banana flesh, steam blanching being the most effective
method for enzyme inactivation. Freezing/thawing processes
produced a significant increase in phenol levels in all samples,
due to cellular breakdown. After microwave heating browning
processes occurred while steam-treated samples did not exhibit a
significant colour change. Extractable PPO and POD activities in
all banana samples increased as a consequence of freezing/thawing:
steam-blanched slices exhibited lower residual activities. High
correlations occurred between phenols and browning (r=0.86) in
control samples. Blanched samples (microwave or steam) only
exhibited correlations between PPO (r=0.80) and POD (r=0.80)
activities and browning.
WO2015154150
A PROCESS, APPARATUS AND SYSTEM FOR TREATING FRUITS OR
VEGETABLES
Inventor(s): HASTINGS JEFFREY JOHN [AU] +
A process for treating fruits or vegetables to minimize browning
upon subsequent processing, handling, and storage, the method
comprising: (a) separating edible pulp tissue from inedible tissue
of the fruit or vegetable; (b) blanching said edible pulp tissue
in steam for a pre-determined blanching time period at a blanching
pressure that is less than or equal to atmospheric pressure; (c)
cooling the blanched pulp tissue and extracting residual heat from
the blanched pulp tissue; (d) freezing the cooled pulp tissue to
obtain at least partially frozen pulp tissue; wherein the frozen
pulp tissue obtained from step (d) possesses substantially similar
organoleptic properties as freshly separated pulp tissue in (a).
TECHNICAL FIELD
[0001] This invention relates to a process, system and apparatus
for treating cut fruits or vegetables such as Avocados that are
susceptible to browning or discolouration even during
refrigeration.
BACKGROUND ART
[0002] Some fruits and vegetables such as the avocado present
unique challenges to the food industry. Avocados are particularly
unusual because they are highly susceptible to chilling injury. If
they are stored at refrigeration temperatures for very long they
will discolour and develop off-flavours. Whilst many people
throughout the world enjoy eating avocados, difficulties in
storing sliced avocado, and the rapid degradation of their
desirable organoleptic traits once they are cut, implies that they
are not widely used in shelf stable foods. Instead, avocados are
largely consumed when freshly cut such as in salads, in sushi, on
sandwiches, in guacamole, or simply sliced. Moreover, the known
food treatment methods that render most other fruits and
vegetables stable further degrades the avocados at an undesirable
state. Unless avocados are immediately consumed after slicing,
they are difficult to use because their flavour and colour
degrades rapidly. This is true whether or not the sliced avocado
is maintained at room temperature or at refrigeration temperature.
[0003] Conventional food preservation methods that use heat and
pressure tend to activate the native enzymes in the avocado and
undesirably affect texture, taste, and appearance of an avocado
and likely negatively affect the avocado. Avocados have a high fat
content and also contain large amounts of degradative enzymes such
as lipases, lipoxygenases, polyphenoloxidase, and methyl
pectinases. Once an avocado is sliced the enzymes are released.
The enzymes are then able to act upon the fat and other components
of the fruit. The enzymes, in particular the lipases, degrade the
fats and thus off flavours including rancidity are developed.
These enzymes are also responsible for discolouration or browning
of the fruit. This browning at least in part is caused due to an
enzyme called polyphenoloxidase which is also present in
mushrooms, apricots, pears, cherries, peaches, and dates. The
polyphenoloxidase (PPO) oxidizes phenolic compounds in the pulp
tissue of a fruit and causes condensation to form brown or grey
polymers. Whilst in a whole fruit this is not a problem bruising
or slicing disrupt cells in the pulp as a result of which the
enzymes and the phenolic compounds come into contact with each
other and react to form the dark pigments. [0004] Air also acts to
degrade the appearance and the flavour of avocados. The beautiful
bright green colour characteristic of a ripe and freshly cut
avocado is from the chlorophyll present in the fruit. However,
Magnesium in chlorophyll is oxidized upon exposure to the air.
Once oxidized, the chlorophyll changes colour from a vibrant green
to a brownish green colour. Once again this change of colour is
less appetizing in appearance than the bright green of a freshly
sliced avocado.
[0005] Therefore, in view of the above shortcomings there has been
a long felt need for treating fruits and vegetables such as
avocados in a manner that preserves the colour and flavour of
fruits such as avocados even after the avocados are sliced, or in
the case of guacamole preparation, even after the avocados are
macerated.
[0006] The reference to any background information in this
specification is not, and should not be taken as an
acknowledgement or any form of suggestion that the prior art forms
part of the common general knowledge.
SUMMARY OF INVENTION
[0007] In one aspect, the invention provides a process for
treating fruits or vegetables for minimize browning upon
subsequent processing, handling, and storage, the method
comprising:
(a) separating edible pulp tissue from inedible tissue of the
fruit or vegetable;
(b) blanching said edible pulp tissue in steam for a
pre-determined blanching time period at a blanching pressure that
is less than or equal to atmospheric pressure, the blanching time
period being less than a cooking time period required to cook the
edible pulp tissue;
(c) cooling the blanched pulp tissue and extracting residual heat
from the blanched pulp tissue; and
(d) freezing the cooled pulp tissue to obtain at least partially
frozen pulp tissue; wherein the frozen pulp tissue obtained from
step (d) possesses substantially similar organoleptic properties
as freshly separated pulp tissue in (a).
[0008] Preferably, the blanching time period is less than a
cooking time period required to cook the edible pulp tissue.
[0009] As should be relatively clear, the blanching step will
preferably take place without directly contacting edible pulp
tissue with water by immersion. [0010] Preferably, a
pre-determined volume of steam is used for the said blanching step
(b) for a pre-determined volume of edible pulp tissue.
[0011] The steam may circulate about the edible pulp tissue via
natural or forced convection currents. Forced convection will
typically require a circulation device such as a fan or blower.
[0012] In an embodiment, the process further comprises an
additional step of inducing turbulent flow to the steam in the
blanching step (b).
[0013] In an embodiment, the process comprises transporting the
separated edible tissue on a conveyor apparatus to a blanching
chamber for carrying out the blanching step (b). The separated
edible tissue is positioned on an endless conveyor belt driven by
a conveyor drive mechanism. As a result, the separated edible pulp
tissue is passed into the blanching chamber and thereby conveyed
in and out of the blanching chamber.
[0014] The operating speed (Cs) of the conveyor belt driven by the
drive mechanism may be varied by a control system for controlling
a rate of passage of the edible tissue through the blanching
chamber.
[0015] In an embodiment, the freezing step (d) comprises rapid
freezing of at least an outer surface of the edible tissue.
[0016] In an embodiment, after the cooling step, the cooled and
blanched pulp tissue is positioned on a freezing conveyor belt
driven by a freezing conveyor drive and passed into a freezing
chamber for carrying out the freezing step (d) and for passing the
frozen pulp tissue obtained from step (c) out of the freezing
chamber. An operating speed (CF) of the freezing conveyor belt
driven by the freezing conveyor drive may be varied for
controlling a rate of passing the blanched tissue into the
freezing chamber.
[0017] In an embodiment, the blanching step (b) is preceded by a
segmenting step in which the separated edible tissue from step (a)
is segmented into discrete pieces. Preferably, the segmenting is
carried out by slicing the edible pulp tissue into the discrete
pieces.
[0018] The blanching time period may be in the range of 1-10
minutes, preferably 2 -6 minutes and more preferably 3-5minutes.
[0019] Preferably, the freezing step (d) is carried out for a
freezing time period in the range of 2-6 minutes and more
preferably 3-5 minutes. In alternative embodiments the freezing
step may also be carried out for longer time periods in excess of
6 minutes. [0020] Preferably the fruit or vegetable is a fresh
fruit or vegetable in that the fruit or vegetable has not
undergone a freezing process after picking. A preferred fruit is
Avocado.
[0021] In another aspect, the invention provides an apparatus for
blanching segmented fruits or vegetables, the apparatus
comprising: a conveyor system for transporting said fruits or
vegetables from one end of a blanching chamber to an opposite end
, the conveyor system comprising a conveyor belt positioned on two
or more drive rollers for transporting said fruits or vegetables
and adapted to be driven by a drive mechanism; the blanching
chamber comprising a shroud overlying the conveyor belt and in
longitudinal alignment in relation to the conveyor belt to at
least partially enclose steam produced from water in a bath
positioned underlying the conveyor belt and in longitudinal
alignment with the shroud and the conveyor belt; wherein during
use the steam produced in the bath is at least partially enclosed
by the shroud thereby exposing the segmented fruits or vegetables
positioned on the conveyor belt to steam and blanching the fruits
and vegetables in the blanching chamber at a blanching pressure
that is less than or equal to atmospheric pressure.
[0022] Preferably, the conveyor belt is adapted for allowing
passage of steam therethrough from an underside in use position of
the conveyor belt to an in use fruit or vegetable supporting
surface of the belt. The conveyor belt may comprise perforations
for passage of steam therethrough.
[0023] In an embodiment, the apparatus further comprises a control
system for varying an in use belt speed of the conveyor belt
thereby varying blanching time period of the fruits and vegetables
in the blanching chamber. Preferably, the control system is
adapted to vary the in use belt speed with reference to one or
more parameters relating to the segmented fruits and vegetable
positioned on the conveyor belt during use. The control system may
also be sufficiently adapted to prevent the in use belt speed from
being below a pre-determined value of belt speed.
[0024] In an embodiment, the apparatus further comprises a steam
control mechanism for controlling steam volume, steam pressure
and/or steam temperature.
[0025] In yet another aspect, the invention provides a system for
treating segmented fruits or vegetables upon, the system
comprising the apparatus for blanching as described in the
preceding sections and further comprising a cooling apparatus
positioned for receiving and extracting heat from the blanched
fruits or vegetables and a freezing apparatus for receiving the
cooled fruits or vegetables for at least partially freezing the
segmented fruits or vegetables.
[0026] Without wishing to be bound by theory, it is hypothesized
that blanching of the segmented fruits or vegetables for a
designated time period as described in the aforementioned sections
assists in inhibiting the reaction between PPO and the phenolic
compounds present in the edible tissue thereby preventing or at
least reducing the extent of browning in the edible tissue. It is
also hypothesized that cooling and subsequent freezing of the
blanched edible tissue after a designated or threshold time period
assists in preventing the initial blanching progressing to
complete cooking of the edible pulp tissue while at the same time
helps in retaining the browning minimisation effect imparted by
the blanching.
[0027] Preferably, the conveyor system transports blanched fruits
or vegetables to the cooling apparatus and subsequent to the
extraction of heat further transports the cooled fruits or
vegetables to the freezing apparatus.
[0028] In an embodiment, the system further comprises a fruit
segmenting apparatus for separating edible tissue from inedible
tissue of the fruit or vegetable and segmenting the separated
edible tissue to obtain segmented fruits or vegetables received
into the blanching chamber. Preferably, the fruit segmenting
apparatus comprises slicing blades for slicing the separated
edible tissue into segmented fruits or vegetables.
[0029]
BRIEF DESCRIPTION OF DRAWINGS
[0030] Figure 1 is a flow chart of the process in
accordance with a first embodiment of the present invention.
[0031] Figure 2A is a top- down view of an apparatus in
accordance with a second embodiment of the present invention.
[0032] Figure 2B is a side-elevation view of an apparatus
in accordance with the second embodiment of the present
invention.
[0033] Figure 2C is an end-elevation view of an apparatus
in accordance with the second embodiment of the present
invention.
DESCRIPTION OF EMBODIMENTS
[0034] Referring now to the drawings, the process for treating
fruits or vegetables in order to minimise browning upon subsequent
processing, handling, and storage will be explained in greater
detail.
[0035] Figure 1 refers to a flow chart of a process 100 in
accordance with an embodiment of the present invention. In a first
ripeness assessment step 110, whole avocados are classified by
using a penetrometer to classify the avocados on the basis of
their ripeness. In one preferred assessment, avocados with a
ripeness rating of greater than 70 are selected for the process in
accordance with the present invention. The selected fruits are
then collected on an accumulation counter in an accumulation step
120. In a subsequent manual handling step 130, each of the fruits
is then sliced into half using a slicing implement such as a sharp
knife (132) and the pit or the seed is manually removed and
discarded from each of the selected fruits (134) and the
exocarp/skin is peeled by scooping out the edible /mesocarp of the
fruit. The mesocarp is also known as the flesh of the avocado, and
this is the edible and most abundant part of the fruit. The edible
tissue (which is in two parts-peeled avocado halves) is
subsequently transported to a segmenting station 140. The
segmenting station 140 comprises a series of rotating blades which
slices and/or dices the mesocarp resulting in segmented pieces of
the fruit. The segmented pieces are visually inspected at this
stage to ensure that the pieces are separate from each other
before being undergoing blanching in a blanching step 150.
[0036] Referring to Figures 2 A, 2B and 2C, a blancher 500
incorporating the present invention is used for the blanching step
150. The apparatus is mounted on a frame 510 including a plurality
of supporting legs 512 and 514 extending vertically. The frames
support a conveyor assembly 520 with a conveyor belt in the form
of an endless belt 522 supported on rollers (not shown). The frame
510 comprises a shroud in the form of a hood 524 that extends
along the longitudinal direction of the endless belt 522 and is
positioned to be overlying the endless belt 522. The hood 524 is
structurally configured to be in substantial longitudinal
alignment with the endless belt 522. An elongate bath 526 for
containing water is positioned on underside of the endless belt
522 in substantially longitudinal alignment with the hood 524. The
water bath is provided with an inlet means and an outlet means for
supplying water and draining water respectively. The hood 524 and
the water bath 526 positioned on the overside and underside
respectively in relation to the endless belt 526 and together
define an interior space of a blanching chamber 528. In a typical
blanching step 150, the segmented pieces of the fruit from step
140 are positioned on the endless belt 522 at a receiving end 532
of the blancher. A variable speed drive motor 534 is then actuated
to drive the endless belt 524 on the rollers. The drive motor 534
is also connected to a control system 536 that controls the speed
of the drive motor 534. The control system 536 comprises a sensory
mechanism including sensors that are sufficiently adapted to
ascertain parameters such as size, weight etc. of the segmented
fruit pieces positioned on the endless belt 524. The control
system 536 processes the parameters and computes an optimal belt
speed for passage of the segmented fruit pieces through the
blanching chamber 528 in order to ensure suitable blanching. The
control system 536 also controls the belt speed such that the belt
speed does not fall below a pre-set minimum belt speed. It is
important to appreciate that the total time of exposure of the
segmented fruit pieces is directly proportional to the belt speed
of the endless belt 524. The time of exposure of the segment fruit
pieces to a steam environment is critical to achieving the desired
outcome of inhibiting the impact of the 'browning' enzyme
Polyphenoloxidase (PPO) but not exposing pieces for so long that
they tend to 'cook' . Once the conveyor drive motor 534 is
actuated in conjunction with control system 536, the steam control
system 540 is also activated. The steam control system heats the
water contained in the bath 526 positioned underneath the endless
belt 522. As the water in the bath 526 is heated, steam is formed
and the steam (water vapour molecules) rises due to the formation
of convection currents. As the steam starts rising from the bath
it passes through the perforations provided in the endless belt
522. In doing so, the steam contacts the segmented fruit pieces
positioned on the belt during the time period (time of
exposure/blanching time) of being transported from the receiving
end 532 of the blanching chamber 528 to the opposite end of the
blanching chamber 528. The positioning of the hood 524 prevents
the rapid escape of the steam and allows the steam to accumulate
within the blanching chamber 528. It is important to appreciate
that the structural configuration of the hood 524, the belt 522and
water bath 528 is such that the pressure in the blanching chamber
528 never exceeds atmospheric pressure. This is achieved by
providing a blanching chamber 528 that is not sealed from the
atmosphere.
Furthermore, the steam used for the blanching process is not
pressurised in any manner such by use of nozzles, spraying
manifolds etc. before being used for the blanching process of the
present invention.
[0037] Upon exiting the blanching chamber the blanched fruit
pieces are cooled in a cooling step 160. This cooling step should
be carried out preferably as soon as possible in order to extract
heat from the blanched fruit pieces. In the preferred embodiment
of the present invention, the blanched fruit pieces exiting the
blanching chamber 528 from the exit end 537 of the blancher 500 on
the endless belt 522 are then directed into a cooling station 162.
Pre-cooling of the blanched fruit pieces may be carried out by an
air chilling mechanism. The air chiller ducts incoming warm moist
air surrounding the blanched fruit pieces and releases cooled dry
air. The pre-cooling step assists in removing any water that may
have inadvertently condensed on the surface of the avocado pieces.
The pre-cooling step 160 is introduced prior to a freezing step to
lower the heat coefficient and increase freezing efficiency. This
is predicated primarily on commercial reasoning to lower the gas
usage cost of IQF freezing at the subsequent station.
[0038] After the pre-cooling step is conducted, the pre-cooled
avocado fruit pieces are transported out of the pre-cooling
station 162 and subsequently transported into a freezing station
in the form of an Independent Quick Frozen (IQF) tunnel 172 to
carry out a freezing step 170. The primary goal of the freezing
step 170 is to freeze the avocado pieces as fast as possible in
order to minimise water crystallisation of the cut surfaces and
produce a final frozen product that comprises substantially
similar organoleptic characteristics as that of fresh-cut avocado.
To achieve this, Independent Quick Frozen (IQF) freezing
technology is used, with carbon dioxide (C02) being identified as
the preferred refrigerating freezing gas. The endless belt 524
carries the avocado pieces from the pre-cooler station 162 into
the IQF freezing tunnel for a pre-determined freezing exposure
time. The preferable temperature for freezing the avocado pieces
is from -10° F. to -150° F., and more preferably from -70° F. to
-120° F. If the temperature is too low, the avocado pieces cannot
endure such low temperature and cracks or fissures might be
caused. If the temperature is too high, it takes too much time to
freeze resulting in an inefficient operation. The extent of
exposure of the cooled avocado pieces is determined by the belt
speed of the conveyor belt when it is passing the IQF freezing
tunnel 172. In one preferred operating configuration, the belt
speed of the endless belt 522 may be controlled to be the same as
the belt speed used during the blanching step. However, in
alternative configurations, the belt speed may be varied using the
control system 534. The freezing step must at least be carried out
for a sufficient time period that results in formation of at least
a 'crust' freeze on each of the avocado piece subjected to the
freezing step 170. Subsequent internal (core) freezing may be
carried out in later steps. Alternatively, the freezing step 170
may also be carried out for a longer time period to ensure
complete freezing in the IQF freezing tunnel 172. The requirement
of at least carrying out crust freezing limit the extent to which
avocado pieces stick to each other, which is an important
consideration. Rapid freezing is an important step because fruits
such as avocado consist of cells that are filled with water, so
that the simple freezing convection (gas or liquid) causes the
water to freeze forming ice crystals disrupting the structure and
cracking the cell walls of the fruit. By subsequently thawing of
the fruit or vegetable that is frozen by simple freezing, the
water comes out through the cracked cell walls, leaving a texture
that is aesthetically not appealing. The faster the fruit is
frozen, smaller the water crystals; thus less disrupting the cell
walls, wherewith less liquid is released when thawing.
[0039] After the conclusion of freezing step 170, the frozen fruit
pieces exit the IQF tunnel 172 on the endless belt 522 and reach a
packaging station 180. The packaging step 180 mainly requires the
use of suitable packaging such as vacuum seal packaging to prevent
the exposure of the frozen fruit pieces to ambient conditions in
order to avoid contamination. Any other alternative forms of
packaging may also be used in further advantageous embodiments for
avoiding contamination. Another important requirement is to limit
exposure of the frozen fruit pieces to UV light in order to avoid
pigment fading. The sealed fruit pieces may be further packaged
into storage containers such as carton boxes in a further
packaging step 185 before being stored in cold storage in a
conventional cold storage facility 190.
[0040] The frozen avocados produced by conventional methods easily
disintegrate and discolour rapidly at the time of thawing or they
are very expensive. However, the frozen avocado pieces produced
according to the process of the present invention can preserve
their integration, shape and colour for a period of more than 2
weeks after thawing. Moreover, the taste of the avocado pieces
thus produced is maintained in a good condition.
EXAMPLE 1
[0041] In accordance with the ripeness assessment step 1 10
described in earlier sections ripeness assessment of a batch of
avocados with a combined weight of 5kgs was carried out using a
penetrometer and all fruits with a ripeness of greater than 70 N
were selected. The fruits were subjected to steps 1 10 to 140 in
accordance with the present invention to obtain sliced fruit
pieces. Half of the sliced fruit pieces were segregated for the
blanching, pre-cooling and freezing steps in accordance with the
process of the present invention and the other half was marked as
a TEST batch and was left untreated after being sliced into
smaller pieces and used a comparative example. Any fruit with
exocarp (skin) that had been penetrated, was not selected. The
temperature of the core of the fruits was recorded to be in the
range of 9-12°C.
[0042] At the end of the segmentation step 140, the segmented
pieces were visually inspected by personnel and aligned on the
endless belt 522 for maximum orientation with dimensions of the
endless belt 522. The width and length of the endless belt 522
used in
Example 1 were 900mm and 3.5m respectively. Blanching was carried
in accordance with the blanching step 150 for blanching time
period of 3-5 minutes. The belt speed was adjusted using the
control system 534 in order to ensure that the segmented avocado
pieces passed through the blanching chamber 528 for the time
period of 3-5minutes. After the blanching step, the pre- cooling
step 160 was carried out to reduce the temperature of the blanched
avocado pieces to a temperature in the range of 20-25 °C. After
the pre-cooling step, the cooled avocado pieces were subjected to
ICQ freezing in the IQF tunnel in accordance with the rapid
cooling step 170 for a freezing time period of 5 minutes.
[0043] With respect to the shape of the avocado pieces, it was
observed that the original shape of each avocado pieces from
Example 1 was preserved on and after thawing. In relation to any
visually observable colour changes, no significant change was
observed until at least ten days with some individual pieces
retaining their original colour for as long as 14 days.
Thereafter, the surface of the avocado pieces was observed to
become gradually blackened due to oxidization.
[0044] The taste of the thawed avocado pieces was good enough for
eating. Furthermore, long term tests carried out for a 12 month
period have also indicated that the pieces retained their colour
taste and other desired organoleptic properties once they were
thawed after being kept in frozen storage for 12 months.
[0045] The frozen avocados from the untreated batch (the
comparative example) easily disintegrate and discolour rapidly at
the time of thawing. However, the frozen avocado pieces produced
according to the present invention can preserve their integration,
shape and colour for almost 2 weeks after thawing. Moreover, the
taste of the avocado pieces thus produced is maintained in a good
condition.
[0046] Throughout the specification, the terms "edible tissue",
"pulp tissue" and "pulp" refer to the mesocarp of the fruit which
is generally the succulent and fleshy middle layer a fruit located
in between the pericarp (the outer skin) and the endocarp (the
seed). The mesocarp is usually the major part of the fruit that is
eaten, for example, mesocarp makes up most of the edible part of
an avocado. Therefore these terms may refer to the fleshy edible
regions of any fruit.
[0047] In the present specification and claims (if any), the word
'comprising' and its derivatives including 'comprises' and
'comprise' include each of the stated integers but does not
exclude the inclusion of one or more further integers.
[0048] Reference throughout this specification to 'one embodiment'
or 'an embodiment' means that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the present invention.
Thus, the appearance of the phrases 'in one embodiment' or 'in an
embodiment' in various places throughout this specification are
not necessarily all referring to the same embodiment.
Furthermore, the particular features, structures, or
characteristics may be combined in any suitable manner in one or
more combinations.
[0049] In compliance with the statute, the invention has been
described in language more or less specific to structural or
methodical features. It is to be understood that the invention is
not limited to specific features shown or described since the
means herein described comprises preferred forms of putting the
invention into effect. The invention is, therefore, claimed in any
of its forms or modifications within the proper scope of the
appended claims (if any) appropriately interpreted by those
skilled in the art.