“Continuous Decontamination
Plants for
Spices and Herbs”
INTRODUCTION
In this documentation you will find information about two different continuous
steam decontamination systems.
The first chapter deals with systems suitable for direct steam treatment at temperatures above 100°C. (“Continuous steam sterilizing / pasteurizing systems”).
The second chapter deals with systems for direct steam treatment at temperatures
below 100°C. only (“Natural low temperature steam pasteurization”).
“CONTINUOUS STEAM STERILIZING / PASTEURIZING SYSTEMS”
The “ Continuous Ventilex “ system has been developed for the decontamination of herbs, spices,
seeds and nuts to make them safe for human consumption without adverse effect on the
organoleptic characteristics and appearance ( flavour/taste and colour).
Special design features allow for the processing of ground products as well as whole products.
The word “decontamination” is used as the process aims at a safe product and not at a sterile
product; this means that micro-organism that are hazardous for heath or causing food spoilage
shall be eliminated.
Many processing plants on the market are able to comply with these conditions, but not all of them
without adverse effect on the quality of the final product that should please the consumer.
Pasteurizing and sterilizing of milk in the dairy industry has learned that “IN-FLOW” processing
in a ST-HT (short time-high temperature) process gives products with better organoleptic
characteristics than has been possible with a batch process because the heat load on the product
could be reduced by fast heating and fast cooling.
The same applies in principle for heat sensitive herbs and spices and especially if large quantities
per hour need to be decontaminated.
The total treatment time in so-called batch autoclaves might take as long as 45 minutes.
The process time for the product in the continuous Ventilex autoclave is generally 25-35 seconds
after which the product meets a flow of sterile filtered air for cooling and drying in the Ventilex
fluid bed dryer/cooler which is directly connected to the sterilizer (see attached diagram).
Cooling and drying of the product in a batch autoclave is mainly obtained by the application of
vacuum after the product has reached the required sterilizing temperature.
It is the vacuum applied in batch autoclaves that extracts an important quantity of the essential oils
while the long heat treatment has an adverse effect on the appearance of the decontaminated
product.
With the Ventilex concept the product is cooled to a temperature below 55 degree C within 30
seconds, which means that the product is never longer subjected to a temperature above 55 degree
C longer than one minute.
120
whole black pepper
herbs
80
60
Decontamination
temperature [°C]
100
40
20
0
40°C
30°C
25°C
drying
1
2
cooling
3
time [minutes]
4
5
6
The “log-reduction” with the Ventilex system is mainly a function of the chosen steam
temperature which is infinitely variable adjustable between 102 and 122 degree C.
The final moisture content of the product leaving the dryer/cooler is mainly a function of the
selected air temperature in the drying section.
Typical time temperature curves for whole pepper grains as well as herbs are shown on the
time/temperature diagram herefor.
Typical steam temperatures in the autoclave are 119-120 degree for whole black pepper, 116-118
degree C for paprika powder and 102-105 degree C for herbs like mayoram and Basil.
The temperature will depend on the initial plate count, type of micro organism to be removed and
particle size. Heat resistant spore formers like Bacillus Cereus require a minimum temperature of
115 degree C.
The diagram here after gives results regarding the treatment of paprika powder which has been
especially selected for a test having 10.000 Cfu/g Bacillus Cereus before and after treatment as
well as for Rosemary. (A total count of < 100 Cfu/gram after treatment means that the micro
organism is not detectable.)
Example of changes before and after treatment
Product
Sweet
Paprika
before
treatment
Sweet
Paprika
after
treatment
Rosemary
Before
treatment
Rosemary
After
treatment
Total count
Mesophile
Aerobe
bacteria’s
Cfu/g
Yeasts
Cfu/g
Moulds
Cfu/g
Ebtero
Bacteriaceae
Cfu/g
Aerobesporeformer
Cfu/g
Bacillus
Cereus
Cfu/g
ColorValue
ASTA
units
1300000
400
200
7000
1300000
10000
95
1000
absent
absent
absent
1000
< 100
93
360000
1000
20000
56000
280000
Not
checked
Not
checked
0,7
<100
absent
absent
absent
absent
Not
checked
Not
checked
0,7
Volatile
Oils
Ml/100g
The important result was that Bacillus Cereus was not detectable after treatment while the color
value showed only a very small change from 95 to 93 ASTA.
For Rosemary there was no change of oil content.
Another test with black pepper showed a reduction from 4.000.000 Cfu/g to 100 while the
reduction of oil was only from 4 to 3,97 %.
Typical design details of the Ventilex sterilizer are the self cleaning rotary valves for product feed
and discharge and the variable speed shaker bed serving the internal conveying of the product
through the system in a way that the difference in treatment time for each part of the product
flow is less than 4 %.
The Shaker bed design allows for automatic CIP (cleaning in place).
The Ventilex system has been validated by the FDA in the USA.
The system is controlled by a central control panel validated for data logging (see picture).
Microbiological quality of products treated with the Ventilex system:
Total count:
less than 10.000 Cfu/g
Enterobacteriaceae:
less than 10 Cfu/g
Salmonella
absent in 25 grams
Yeasts and moulds:
less than 10 Cfu/g
Bacteria spores:
Bacillus Cereus less than 100 Cfu/g
Clostridium Perfringers less than 100 Cfu/g
Staphylococcus Aureus less than 100 Cfu/g
Not every product requires treatment with high pressure steam at temperatures above
100 degree C and Ventilex has successfully designed and supplied continuous pasteurizing systems for almonds, seeds, air dried vegetables, herbs, garlic flakes and onion
flakes. The system has been validated by the FDA after performing a 5 log reduction
on Salmonella.
The next chapter describes the low temperature pasteurization.
Decontamination plant shows: dust separator, dryer/cooler and sterilizer
Side view of Bokfard sterilizer with rotary product inlet valve
Photo shows sterilizer dryer / cooler and cyclone assembled in the Ventilex factory.
“NATURAL LOW TERMPERATURE STEAM PASTEURIZATION”
The pasteurization process aims at the elimination of micro organism hazardous to Heath.
We distinguish two decontamination processes that is to say with low temperature steam below
100° C. and with high temperature steam between 100°C. and 121° C.
It is common knowledge that the treatment temperature is more important for the sterilizing effect than the treatment time provided there is a wet environment such as saturated steam. (hot air
has hardly any sterilizing effect).
It is also common knowledge that long treatment times at increased temperatures cause chemical
changes and have an adverse effect on product quality.
Hence a treatment at High Temperature during a Short Time, a so-called HT-ST treatment is the
right solution.
Pasteurized milk is a typical example of a product treated according this principle and everybody
who drinks pasteurized milk knows that it tastes like fresh milk. This is because it has been
pasteurized in a continuous flow.
Milk is a liquid and this liquid is treated “IN-FLOW”.
We, at Ventilex realized that we had to develop an “In-Flow process for solids” to become
successful in supply of decontamination systems for herbs, spices, nuts and seeds, whole products
as well as powders.
The only option to get an In-Flow HT-ST sterilization is to feed the product in a continuous flow
into a continuous autoclave where the product comes in contact with saturated steam of an
accurately controlled temperature.
The Ventilex continuous autoclave is identified by self cleaning rotary pressure locks
serving the product feed into the autoclave as well as the product discharge out of the autoclave.
From the discharge the product is fed directly into a sanitary fluid bed dryer/cooler where the
product is cooled and dried to its initial moisture content or to the exact moisture content desired
by the company.
Heating to the required process temperature takes less than 2 seconds by the condensing steam
and cooling to 50 C in the fluid bed dryer/cooler takes 30 seconds by evaporation of the steam
condensed on the product.
A filter unit provides the sterile air for the drying and cooling of the decontaminated product.
Another development has been the shaker bed conveyor that makes a very short treatment time
possible while it also guarantees that there is always exactly the same treatment time for every
part of the product flow.
The systems with rotary pressure locks are for treatment at temperatures above 100 C which is
imperative for “sun dried” products like pepper, paprika and many other seeds, herbs and spices.
For “air dried” vegetables, herbs and nuts the heat treatment can be much milder and we should
call this treatment “IN-FLOW” pasteurization as a treatment of 20 –30 seconds at 90 C will be
amply sufficient .
The In-Flow pasteurization plant is shown on the next page and photos here after show details of
various low temperature steam decontaminating plants.
Pasteurizations system for almonds in the USA.
(See on the Internet: www.nutpasteurization.com)
Continuous steam pasteurizer in China for the decontamination of onion flakes and garlic flakes.
The photo shows dust and hepa filter, ventilator and air heater for sterile air supply to a
Ventilex fluid bed dryer / cooler.
Example of setting process parameters.
Nut pasteurizer and cyclone in the USA.