Dr/ Hesham kotb D.V.M D.P.D Veterinary section head Alwadi poultry company K.S.A

Produce H+ (as H3O+) ions in water (the hydronium

ion is a hydrogen ion attached to a water molecule)

Taste sour

Corrode metals

Electrolytes

React with bases to form a salt and water

pH is less than 7

Turns blue litmus paper to red “Blue to Red A-CID”

• Strong acids :

• The dissociation in solution Is always complete and no reversible

• AH -> H+ + A-

• Weak acids :

• The dissociation is not total , balance between 2 forms, one called dissociated, the second called non dissociated :

AH <-> H+ + A-

• Like any chemical balance this equilibria allways respect stricly a chemical rule due to the equilibrium constancy K

• K = [H+][A-]/[AH]

• we speak about Ka, K for constancy a for acidity

• The higher the constancy, the more H+ is produced, so the stronger is the acid

• pKa is equal to -LOG10 of Ka, the lower the pKa, the stronger the acid

• Acid classification :

• Some mineral acids are also weak acids :

• 2 of them are fundamental for the regulation of pH in the organism :

• Phosphoric acid :

• H3PO4 H+ + H2PO4- pKa1 2.2

• H2PO4- H+ + HPO4-- pKa 7.3

• The second acidity is the main important in the regulation of intracellular pH and urine pH

• Carbonique acide :

• H2CO3 H+ + HCO3- pKa = 6.3

• This reaction is fundamental for blood, intestinal environmental pH balance

• So mineral acids in some case means also physiological and even fundamental for organism metabolism regulation

Organic acids are carboxylic acids with the general formula of R-COOH, with the "R" group representing a fatty acid chain of variable length, and the "COOH" group representing the carboxyl group that is the source of the donatable H+.

Examples of organic acids include formic , acetic ,lactic ,propionic

Organic Acid is an Organic Compound with Acidic properties associated with their Carboxyl group –COOH

Fumaric acid HO2CCH=CHCO2H

Malic acid HO2CCH(OH)CH2CO2H

• pKa tells you if a given molecule is going to either give a proton to water at a certain pH, or remove a proton • A pKa of 2 for substance “X” means that at a pH of 2, X is at its equilibrium point. • If the pH falls to 1, then X will accept a proton because there are so darn many available (pH 1 means very acidic—lots of protons) and form XH • If the pH rises to 3, then X will give up a proton and exist as X- • At any pH above 2, X is a stable ne

For acetic acid, the pKa is 4.76 • Say you have equal concentrations of acetate (the conjugate base of acetic acid) and acetic acid, what would the pH be? • pH = pKa (4.76) + log (acetate-)/(acetic acid) • The log of 1 = 0 • So the pH is 4.76 when acetate and acetic acid are at equilibrium (this is a weak acid)

That means at PH 4.76 about 50% of acteic acid will be in dissociated form while other 50% will be in non dissociated form

Inorganic acids have a very low pKa, which means that they are mainly present in dissociated form. Therefore, they will not be able to enter the bacterial cell and disturb proliferation via the same route. They also have a large chloride, phosphate or sulphate component in the molecule will disturb acid base balance

Organic acids have antibacterial effect on gram negative bacteria specially short chain acids

The antibacterial effect is mainly due to the un dissociated form of the carboxylic acid that act by 2 mechanisms

1- depleting bacterial cell energy to get rid of H+ 2- COO- group react with bacterial DNA the lower the pKa of the organic acid (the higher

proportion of dissociated form) the greater is its effect on the reduction of stomach pH and the lower its antimicrobial effect in the more distal portions during its transit through the digestive tract

Mode of action of organic acids against gram-negative bacteria 1. Undissociated organic acid entering bacterial cell. 2. Dissociation of proton, leading to pH reduction. 3. Expulsion of proton by energy-demanding process. 4. Inhibitory effect of acid anion on DNA

Acid Formula MM (g/mol)

Density (g/ml)

State pKa Solubility in water

Corrosivity

MEn MJ/kg

Taste

Formic HCOOH 46.03 1.220 Liquid 3.75 “ +++ 11.34 —

Acetic CH3COOH 60.05 1.049 Liquid 4.76 “ ++ 12.19 -0

Propionic CH3CH2COOH 74.08 0.993 Liquid 4.88 “ ++ 17.78 -0

Butyric CH3CH2CH2COOH 88.12 0.958 Liquid 4.82 “ + 22.43 +

Lactic CH3CH(OH)COOH 90.08 1.206 Liquid 3.83 V + 14.53 ++

Sorbic CH3CH :CHCH :CHCOOH

112.14 1.204 Solid 4.76 S + 0

Fumaric COOHCH :CHCOOH

116.07 1.635 Solid 3.02 4.38

S + 0

Malic COOHCH2CH(OH)C

O

OH 134.09 1.601 Liquid

3.40 5.10

“ 0 9.79

Tartaric COOHCH(OH)CH(O

H) COOH

150.09 1.760 Liquid 2.93 4.23

V +

Citric COOHCH2C(OH) (COOH)CH2COOH

192.14 1.665 Solid 3.13

4.76 6.40

V 0 10.29 ++

Phosphoric H3PO4 2.0, 7.0 12.0

“ ++++

Butyric acid

pH 1.8 2.8 3.8 4.8 5.8 6.8 7.8 8.8 9.8 10.8 11.8

BuCOOH 99.9 99 90 50 10 1 0.1 0.01 0.001 0.0001 0.00001

BuCOO- 0.1 1 10 50 90 99 99.9 99.99 99.999 99.9999 100

Formic acid

pH 1.8 2.8 3.8 4.8 5.8 6.8 7.8 8.8 9.8 10.8 11.8

HCOOH 99 90 50 10 1 0.1 0.01 0.001 0.0001 0.00001 0.000001

HCOO- 1 10 50 90 99 99.9 99.99 99.999 99.9999 100 100

Acid pKa1 pKa2 pKa3

Hydrochloric 0

Phosphoric 2.15 7.09 12.32

Fumaric 3.03 4.54

Citric 3.13 4.76 6.4

Formic 3.75

Lactic 3.83

Benzoic 4.19

Acetic 4.74

Sorbic 4.76

Butyric 4.8

Propionic 4.87

Conclusion : lower pKa makes lower pH

More efficient to reduce pH

CH3 - [CH2]2 - COONa

D,L-MALIC ACID:

Water-soluble (55,8 g in 100 g of water)

pK1: 3,4 pK2: 5,1

FUMARIC ACID:

Slightly soluble in water (0,63 g/100 g of

water)

pK1: 3,03 pK2: 4,54

citric acid is an organic acid commonly used by poultry producers for acidifying their water. Citric acid is an excellent acid for this mainly because it’s inexpensive but also because it contains three carboxyl groups which help decrease the pH of the water quickly. pH of the water is important when you are using sanitizers, because lower pH allows sanitizers to be more effective against certain microorganisms. However, citric acid does not have good antimicrobial activity.

as we formulate our diets based on the weight of the ingredients, not their molarity. Therefore, there are benefits to higher acid density in the form of greater concentration of active ingredient within the same formulation space in the mixer

formic acid has a particular advantage over the other acids due to its simplicity and lower molecular mass

formic acid is the simplest of the organic acids, with the R-group consisting of a single hydrogen atom, and as a result has the lowest molecular mass (46 g/mol) and greatest molecular density of any organic acid (21.7 mol/kg).

In same quantities, Formic as a smaller molecular weight so can bring

more acid per kg

But as a smaller molecula, its absorption is also quicker in the

stomach

Crop

pH 5.5

Proventriculus

pH 2.5 – 3.5

Gizzard

pH 1.5 – 3.5

Duodenum pH 5 - 6

Jejunum pH 6.5-7

Ileum pH 7 – 7.5

Cæcum pH 6.9

Colon-Rectum

The bactericidal effect of the organic acids is : benzoic acid > fumaric acid >lactic acid > butyric acid > formic acid > propionic acid

Poultry diets usually have high alkalinity characteristics: (very rich in protein and mineral substances). Vegetal protein and calcium carbonate meals in feeds have a strong buffer function characterized by such a high buffer capacity can compromise the intestine capability to keep an acidity level that can support growth and in some cases, maintain beneficial intestinal microflora.

Buffering capacity or B-value in a feed is often expressed as meq of 1.0 M HCl required to acidify 1 kg of material (feed or feed ingredient) to pH 3 -5. Usually, the amount of 0.1 M HCl required to reduce the pH to 5 of 10 g feed in 90 ml distilled water is represented as buffering capacity 9.

1. pH of feed in water slurry and B-value are not related. 2. pH of feed ingredients are variable but B-values are much more variable. 3. Cereal has low B-values. 4. Protein sources have high B values. 5. Mineral sources such as DCP has high B-value. 6. Limestone has a very high B value. 7. B-values can be additive if same end point is used: say pH 5.0 8. B-values of different batches of a feed ingredient may vary. 9. It is not easy to calculate B value of a final feed from B value of ingredients.

In young animals, capacity to secrete gastric juice is limited. High B-value may pose problems. Pathogenic bacteria multiply in the digestive tract.

The recommended B-value for poultry is about1-10 for 1-10 days age and 10-20 for 10-30days age

Bactericide action of Acids mix

R-COOH

3.8

pKa

R-COO-

H3PO4 acid effect R-COO- R-COOH

Lowering the pH, phosphoric acids makes the undissociated form dominant

When acids will react with other components, the strongest acid in a mix is allways the first one to react. So phosphoric acid reacts always before organic acids in the mix, preserving their efficiency

Organic acids can have a more bactericide effect

Acid Effective Less

Effective Not

Effective

Formic acid Yeasts& Bacteria -

(E.coli&Salmonella) LA-bacteria&

Moulds -

Acetic acid Many species

of bacteria Yeasts & Moulds -

Propionic acid Moulds Bacteria Yeasts

Butyric acid Bacteria

(E.coli&Salmonella) - -

Lactic acid Bacteria - Yeasts &

Moulds

Citric acid - Bacteria -

Malic acid Some bacteria

& Yeasts - -

Sorbic acid Yeasts, Moulds

& some Bacteria - -

Antimicrobial gram -

Nutritive pH lowering taste

corrosivity

Formic Acid (C1)

+++ ++ +++ ---- ---

Acetic acid (C2)

+++ ++ ++ ++ --

Propionic acid

++++(Y+M) + + ± -

Lactic acid ++ +++ ++++ ++ +

Fumaric acid (C7)

-- ++ ++ ± ±

Sorbic acid +++++

Benzoic acid +++++

Application

Sprayed as a liquid directly in to feedstuff & compound feed

Powder form are added directly or via premix

Liquid form via drinking water

A small molecule penetrates the bacterial cell more easy Calcium Butyrate has a lower anti-bacterial effect, as its molecular weight is 2 X higher than Sodium Butyrate ( resp. 216 and 111, resulting in less diffusion capacity)

Sodium Butyrate is perfectly water-soluble (1.0 kg in 1 kg water)

Calcium Butyrate’s water-solubility is poor (0.3 kg in 1 kg water)

the higher the solubility, the easier the reaction to salt vice versa ;

otherwise it only stays as a crystal

Calcium Butyrates are not spray-dried ( 1 - 2% free, volatile But.-acid)

(Na-Butyrate) is spray-dried (< 0.1% free, volatile But.-acid)

(Na-Butyrate) high concentration active ingredient

(Na-Butyrate) captured and covered odeur Calcium Butyrate has a much stronger ‘typical’ odeur/smell than spray-dried Sodium Butyrate (= related to the level of ‘free buteric acid’, which is an extremely volatile molecule) Calcium Butyrate have lower levels of active ingredients, and often contains a rather high level of (non-nutritional) anti-caking products Dust level (measured by ITECH) is twice as high in Ca-Butyrate (>4%) compared to (Na-Butyrate) (2%) (Na-Butyrate) (spray-dried) has a much more uniform particle size than Ca-Butyrate (dry mix)

4 5 6 7 8 3

E. COLI

CLOSTRIDIUM

SALMONELLES

pH

4,4 6 8

7,8

6,8 4,2

5

Log 10 Crop Gizzard Duodenum Ileum Caeca

Lactobacilli 8.7 7.3 8.0 8.6 8.7

Enterococus 4.0 3.7 4.0 4.2 6.7

Coliformes 1.7 - 2.0 2.7 5.6

Yeast 2.7 - 1.7 - 2.0

Clostridia - - (-) (-) 9.0

Anaerobes - - - - 10.0

Streptococus anaerobic - - - - 10.0

Power of the acids at pH 4,50

% w/v of an acid required to lower pH of 0,05 N NaOH

Propionic Ac.

Acetic Ac-

Lactic Ac. 80 %

Citric Ac.anhydrous

Phosphoric Ac 85 %

Malic Ac.

Formic Ac.

L-Tartaric Ac.

Fumaric Ac.

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

Formic acid.

Propionic acid. Acetic acid. Benzoeic acid.

Citric acid. Sorbinc acid. Lactic acid

Micro Organism. ( bacteria.) Molds, anti Microbial Bact. / molds / yeasts. Most effective against

yeasts and bacteria. Palatability improver. Yeasts. Active in intestinal

tract.

Gastrointestinal tract

compartment

Transit time

Minutes

pH

Crop 50 5.5

Gizzard 90 2.5 - 3.5

Duodenum 5-8 5 - 6

Jejenum 20-30 6.5 - 7

Ileum 50-70 7 - 7.5

Rectum 25 8 Source: Dr HC Indresh

Moulds are eukaryotic cells and hence have a more complex structure than bacteria, which are prokaryotes and therefore more simple in nature. This more complex structure is more easily crossed by propionic acid due to its lipophilic nature, making it the acid of choice for mould inhibition

liquid propionic acid is very suitable for application onto high moisture whole cereal grain where mould growth is very likely and a rapid control measure is needed

Combining different short chain fatty acids (e.g. propionic acid in combination with acetic or formic acid) is known to enhance the mould-reducing effect of individual acids.

lipophilic acids such as propionic acid may make the bacterial cell membrane more permeable to other acids such as formic acid

Lactic acid can be converted to butyric acid by bacteria in the gut, and butyric acid is believed by some to be a preferred energy source for enterocytes.

Buffered acids have a weaker effect on pH reduction. Buffered acids are acids mixed with a conjugate base. The conjugate base in this mixture neutralises released protons, therefore the pH reduction will be less compared with single acids. buffering acids leads to a higher fnal pH of a solution than when unbuffered acids are used. This is of importance in the acidifcation of drinking water, because when the pH of the water is too low, water intake might be reduced. Besides this, a suffcient dosage of organic acids can be added to the water for preservation while limiting the reduction of water pH. Therefore, using a synergistic blend of free and buffered acids is the most favourable strategy for product effcacy

The main reasons to use acid salts are to facilitate handling and to reduce corrosion. Pure acid salts are generally dry powders, which can be more convenient than liquid acids depending on your mill, and they are less corrosive. For example, by converting part of the formic acid in Amasil NA to sodium formate and thereby reducing the free formic acid concentration to 61%, we can cut the corrosion rate on carbon steel by a factor of 10× (Figure 5). However, that benefit comes with a cost of slightly reduced potency, which is why our recommendations for Amasil NA are slightly higher than for Amasil 85

The tradeoff is the result of the lost H+ that drives product efficacy, and replacing it with sodium. This tradeoff is exacerbated the more the product is buffered, with fully buffered acid salts (pure Na-formate or Ca-formate for example), being incapable of feed acidification at all. Therefore, a balance must be struck between the two competing objectives

However, the mode of action of organic acids (Figure 1) depends on free hydrogen ions to activate the organic molecule into the dissociated or un-dissociated form respectively. Unlike organic acids,salts do not have an hydrogen ions to release. The chemical fact: “the stronger acid releases the weaker one from its salts” is still valid and can be illustrated by the following reaction:

This will improve digestibility in the stomach of adult monogastric animals better than in younger animals, whose stomach produce less HCl. Organic acids with high molecular weight (M) like citric acid, fumaric acid and the inorganic acid phosphoric acid can not penetrate through the cell wall as they do not have a lipophyl character. At higher pH levels (6-7) formic acid and lactic acid are already dissociated outside the bacteria cell and become negatively charged are no longer able to penetrate into the bacteria. This effect can also be seen in Table 2, which shows that there is no antibacterial activity left at pH 7.