This document provides an overview of mould control in grain and feed preservation. It discusses how moulds thrive in conditions of high moisture and warm temperatures. Organic acids like propionic acid are effective at inhibiting mould growth by disrupting the mould cell's pH and metabolism. Traditionally, propionic acid has been used, but a new formic-propionic acid blend offers an alternative with ammonium-sodium buffering to reduce volatility and corrosivity. Laboratory and field tests show this new product effectively controls mould growth in grains during storage.

1. Digital Re-print - May | June 2012
Mould control in grain and feed preservation
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2. FEATURE
MOULD in grain
and feed
CONTROL preservation
by André Meeusen, application manager and Yvonne van der Horst, technical manager,
Kemira ChemSolutions b.v., The Netherlands
M
oulds are ubiquitous and unavoida- a widespread application, however, this is not shelf life, maintains nutritional value, and prevents
ble contaminants in all animal feeds. an efficient way to tackle the problem as they formation of mycotoxins.
Virtually all animal feeds contain damage the nutritional quality of feeds. These
moulds and viable mould spores which continue toxin binders, which usually contain different Mould and moisture
to pose a threat to grain quality. types of clay minerals, are not that efficient and Development of moulds in feed depends on
may even compromise nutrient digestibility. the interaction of several factors, including the
Moulds are fungi which are distinguished Moreover, mycotoxin contaminated feeds can presence of spores, the availability of nutrients,
by the formation of mycelium (a network impair the animals’ health and productivity duestorage time, temperature and moisture. Water
of filaments or threads), or by spore masses. to loss of appetite, feed refusal, allergic reactions,
activity, i.e. the presence of free water, is the
Conditions that favour moulds include moisture reproductive failure, suppression of the immunemost important factor in the growth of moulds.
levels higher than 12 percent, warm tempera- system and even mortality. Indeed, microbial spoilage of food and feeds
tures, the presence of oxygen, and prolonged Contamination by moulds and consequently, occurs at different levels of moisture and the
storage time. the production of mycotoxins, can be greatly water activity (aw) concept describes the water
Many moulds are toxigenic and produce reduced by using organic acids as inhibitors. available for microbial growth.
mycotoxins, a secondary metabolite created by Organic acids effectively inhibit the growth of Most feed mills optimise or maximise mois-
moulds that is toxic to organisms other than the moulds, yeast and bacteria in different types of
ture levels during feed production to com-
mould itself. The growth of moulds and produc- feedstuffs and prevent recontamination after pensate for losses that occur during grinding,
tion of mycotoxins by these moulds in feed production of the compound feed. This extends pelleting and cooling processes. Moreover, a
ingredients can cause significant eco- sufficient moisture level reduces the
nomic losses. They consume valuable energy usage during the pelleting
feed nutrients such as vitamins and process and results in better pellet
amino acids and they convert energy quality. The drawback of increasing
into water and CO2 and can cause moisture levels is that increasing levels
temperature increase as a result of of free water creates ideal condi-
their carbohydrate metabolism (see tions for rapid mould growth and the
below) development of mycotoxins. Moulds
C6H12O6 + 6 O2 => 6 CO2 + 6 and yeast grow at aw > 0.75 and aw >
H2O + Heat 0.85 respectively.
Mould growth depletes the nutri- Products that protect feeds against
ent density and affects feed palatabil- mould growth and at the same time
ity and consequently decreases feed lower the aw are based on calcium
intake. Moulds cause lipid oxidation or sodium propionate. Propionic acid
and pigment deterioration and are is reacted with calcium or sodium to
detrimental to animal health, perform- produce a salt with high propionic acid
ance and reproduction. The most level, 76-78 percent depending on
frequently found mycotoxins are afla- Fig 1: Assessing the activity of Kemira Mould Control the salt form. The acid is completely
toxins and ochratoxin produced by SP1 (calcium propionate) using a CO2 test on mash buffered, has a good solubility, is safe
Aspergillus, the latter are also produced feed. (Kemira ChemSolutions, Tiel, The Netherlands). to use and easy to handle. Their
by Penicillium and zearalenone and efficiency in shelf life extension when
trichothecenes produced by Fusarium used in feeds is dose related and can
moulds. be easily demonstrated by an in vitro
accelerated method, increasing mois-
Toxin binders vs. organic ture content and storage temperature,
acids by measuring the CO2 production
Animal feed is susceptible to mould over time. An efficient preservative
growth. The microbiological quality of effect is obtained up to the moment
feed is a comparatively unexplored that CO2 production starts to increase
area but is receiving more attention (Figure 1).
due to the recognition of mycotoxins
as a widespread economic threat. Fig 2: Aspergillus niger growth inhibition efficacies Grain preservation
of organic acids on ground whole wheat grains.
The use of toxin binders in feed is Animal feeds generally contain
18 | may - June 2012 Grain &feed millinG technoloGy

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4. FEATURE
of propionic acid Finland and compared to ammonium buff-
Table 1: Mould inhibiting and killing-off effect of Propionic acid (Kemira
Mould Control LP1) and formic – propionic (Kemira Mould Control LF1) to overcome the ered propionic acid (Kemira Mould Control
buffered products in highly challenged conditions (Wessling 2011) odour and corro- LP1 NC). Figure 2 shows that the initial
sion problems. inoculation with Aspergillus niger in grains
TREATMENTS RESULTS To enter into without preservatives resulted in significant
0.day 7.day 14.day the mould cell, the growth during the first week. Both Kemira
Name % Mould cfu/g Mould cfu/g Mould cfu/g acids have to pass a Mould Control LP1 NC and Kemira Mould
double barrier, the Control LF1 at 0.2 w/w-%, inhibited growth
Positive control: ASPERGILLUS inoculated 3.5∙104 4.7∙105 2.0∙107 cell membrane and of Aspergillus niger in grinded whole wheat
the outer cell wall of grains over a 2 weeks period and total kill
Kemira Mould Control LP1 nc 0,4 1.0∙103 <50 <50
these moulds. Inside off was obtained with both products at 0.4
Kemira Mould Control LF1 0,4 8.5∙102 <50 <50 the moulds the w/w-%.
Positive control: FUSARIUM inoculated 2.2∙105 3.6∙105 6.4∙106 organic acids dissoci- The same laboratory tests have been
ate decreasing the repeated in Wessling Laboratories. Also
Kemira Mould Control LP1nc 0,4 2.0∙104 1.0∙102 <50
intracellular pH and here the inclusion of 0.4 percent with both
Kemira Mould Control LF1 0,4 1.0∙102 <50 <50 compromising the products showed to be efficient in killing off
Negative control <50 <50 <50 cell metabolism. The both types of moulds during a two weeks
three-dimensional incubation period. The Fusarium moulds
mould spores which originate from raw materials structure and the lipophilic character of propi- seemed somewhat more sensitive to the
used. The three genera of moulds - Aspergillus, onic acid seems to play an important role for the formic acid based mould inhibitor with total
Penicillium and Fusarium cause most cases of acids to pass through this double barrier. kill off at seven days already (Table 1).
mycotoxin contamination in many grains and Kemira has developed several mould con- The efficacy of Kemira Mould Control LF1
their byproducts and in vegetable proteins. Their trol products containing appropriately buffered was further assessed in a simulated field trial at
optimal growth is mostly influenced by tempera- acids avoiding the typical drawbacks of straight Wageningen UR, The Netherlands. The trial
ture and this determines their global presence. acids. The organic acids in the liquid Kemira measured mould and temperature develop-
Aspergillus and Penicillium species will grow Mould Control product range are buffered ment of fresh harvested grains during a four
better in warmer-tropical climates whereas with ammonium or sodium, ensuring reduced month storage period at ambient temperature
Fusarium moulds prefer cooler temperate cli- corrosivity and volatility and a long lasting pres- and results were compared to Kemira Mould
mates. Moulds are obligate aerobe and their ervation effect. Control LP1nc.
proliferation can thus be controlled by oxygen Ammonium buffering has the advantage The treatment with the formic acid based
free storage, such as silage. They consume of delivering a proton H+ supporting a more Kemira Mould Control LF1 at 0.7 percent
carbohydrates and provoke fat hydrolysis leading effective mould inhibitory effect. The inclusion of showed the biggest effect in preventing the
to nutritionally low quality grains. Organic acids a lipophilic compound assures a better surface temperature to increase. It was significantly
contact with grains and an easier penetration (P<0.05) lower than both the positive control
Table 2: Mould counts in freshly harvest rolled into meals and feeds. It will also improve the (propionic acid based) and negative control.
wheat after three weeks storage with and water binding capacity of feed materials and Moreover, results showed that Kemira Mould
without treatment (Aberystwyth University) lower the water activity of feeds. This extends Control LF1 at 0.4 percent is as effective in
Mould count the shelf life, maintains the nutritional quality, and inhibiting mould growth and preventing tem-
Treatment (cfu/g) prevents the formation of mycotoxins in feeds perature increase in freshly harvested grains with
and feedstuffs. high moisture content (17.6%) as the propionic
acid based Kemira Mould Control LP1nc. Mould
Kemira Mould Control LP1 nc 227
Formic acid based mould inhibitor growth was reduced from 5 log platable fungal
Kemira Mould Control LF1 40 Traditionally propionic acid is used against colonies per gram in the non-treated grains
Untreated >1,500,000 mould and mycotoxin formation. The relative down to 1.34 log/gram and 1.15 log/gram
shelf life depends to a great extent on the pro- respectively.
are known in the feed industry as an effective pionic acid content. Indeed, the lowest survival This was also confirmed in a field trial in UK,
and affordable tool to control mould growth rates for Fusarium spp. and Aspergillus niger were monitored by Aberystwyth University in which
in grains and their byproducts during transport achieved with the highest actual propionic acid freshly harvested wheat with a moisture content
and storage. contribution, irrespective of the type of mould of 17.9 percent was rolled and treated with
Anaerobic preservation of grains usually inhibitors tested. different dosages of the ammonium-sodium
applies when moisture is very high, from 25 – As the leading global producer of formic buffered formic-propionic acid based product
45 percent. Grains are crimped before ensiling acid-based products for the animal feed industry, or with the ammonium buffered propionic acid
with formic acid based products. Kemira has developed a new liquid mould inhibi- only and stored for eight months in 10 ton bins.
Aerobic preservation is usually done with tor for grain preservation based on formic and At nine litres per ton of grains, both products
whole grains with moisture content between propionic acid with an excellent ammonium- allowed easy storage without any temperature
15 – 25 percent. Typically, blends of different sodium buffering system to minimise volatility increase in the bins during the eight months.
acids or acids with other active compounds are and corrosivity and ensuring proper handling Initial mould counts at three weeks showed
used, with propionic acid being the principle properties. It is activated by lipophilic com- both products to be effective, compared to an
active component. The level of propionic acid pounds. Formic acid does not have this lipophilic untreated sample.
needed under local conditions depends on characteristic but it contains the highest antimi- This makes Kemira Mould Control LF1, a for-
kernel quality, initial mould counts, storage con- crobial properties as this is the smallest molecule mic acid based blend with a novel ammonium
ditions and time. of all the organic acids and has a > 60 percent – sodium buffering and activated by lipophilic
higher number of active organic radicals per compounds, an interesting alternative to the
Straight vs. buffered acids kilogram of pure substance. traditional propionic acid based products, assur-
The mechanism of inhibition of growth The efficacy of such a novel ammonium- ing the fast killing of any mould that appears on
of moulds by organic acids is generally not sodium buffered formic acid based product grains and assuring a save and long preservation.
considered a pH phenomenon. It is the propi- (Kemira Mould Control LF1) on reduction
onate ion or radical (CH3CH3CO0-) that is the of Aspergillus niger in grinded whole wheat More inforMation:
active mould inhibiting ingredient in propionic grains was assessed in a laboratory study Kemira ChemSolutions b.v.
acid, so attempts have been made to use salts done in the Kemira R&D center in Espoo- Email: feed@kemira.com
20 | may - June 2012 Grain &feed millinG technoloGy

6. News May - June 2012 NEWS
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Grain &feed millinG technoloGy may - June 2012 | 3

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