BENZOIC ACID C6H5COOH or C7H5NaO2 p

Dr.rer.agr. BDR Prasantha, Dept. Food Science &Technology, Faculty of Agriculture, University of Peradeniya | 1

BENZOIC ACID

C6H5COOH or C7H5NaO2

andp-hydroxybenzoic acid (paraben)

Benzoic acid Synthesis from toluene

BA- naturally ester in many plant and animal

Most berries contains 0.05%

BApresent as part of hippuricacis (N-benzoylglycine) in mammalian urine : Humans produce 0.44 g/L

BA use fungal skin diseases

Na-benzoate:1st food chemicalpreservative

E numbers –E210, E212 and E213

Antimicrobial agent for large number of foods

Antimicrobial activity

Inactive at pH ≈ 7

More active at low pH

Undissociation forms at low pH

Na-benzoate effective at pH 2.5 – 4.0

Inhibit the some bacteria @ 50 - 500 ppm

Inhibit yeast and mold @ 100 - 500 ppm

Fruit juices > 1% (maximum) benzoates develop disagreeable taste “peppery or burning”taste

Soft drinks (???)

Sauces

Salad dressing

Margarine

Pickles

Use as medicine and cosmetic agent

p-hydroxybenzoichighly effective on MO:

10–100 ppm, totally inhibit gram +ve and gram-ve bacteria

Heptylparaben:

Beer-12 ppm

Fruit drink and Beverage - 20 ppm


Intracellular pH < 5 anaerobic fermentation glucose through phosphofructokinase

Benzoic acid show synergetic effect with both sorbic acid and SO2

Mode of action of chemical preservatives

Taken up by respiring MO cells

Block the oxidation of glucose and pyruvate at acetate level

Inhibit the cellular uptake of substrate

Soluble in cell membrane: act as proton ionophores

Proton leakagehigh into cells: High E needs to maintain cell pH

Disruption in cell membrane activity:low AA transport

SORBIC ACID

Ca, Na or K salt of sorbic acid (CH3CH-CHCH-CHOOH)

Slightly soluble in water and sublime

Maximum use upto 0.2%

Effective against molds andyeastsand some bacteria

More effective in acidic media pH < 6

Sorbic more effective > propionates and benzoates

Effectiveness:

Sorbic acid>Na-benzoates at pH 4 - 6

SA:used for cakes, filling for chocolates and cheese spreads at higher levels than propionates without

adding flavor

Resistance of the lactic acid bacteria at pH > 4.5:

Use as fungistat for lactic fermentation

Effective against:

Staphylococcus aureus

Salmonella

Coliforms

Pseudomonads

Vibrio parahaemolyticus

Sorbates use as fungistats:

Meat, Fish, Cheeses, Bakery product, Fruit juices, Beverages,Salad dressing

Sorbates can use with nitrites for meat product

Mode of action

Inhibition of the dehydrogenase enzyme system Lipophilic acids, sorbate, benzoate and propionate inhibit

MO cell: proton motive force (PMF)


PROPIONATES

Propionic acid is a 3C acid CH3CH2COOH, act as a mold inhibitor

Short-chain FA: affect the cell membrane permeability

It has fungistatic than fungicidalaction

Little or no inhibition of most yeast and bacteria

Low inhibitory effects on yeasts:

Good for bakery dough

Ca and Na salts of propionic acid permitted:

Breads, cakes, cheese

It is found naturally in Swiss cheese

Most active in low acid foods

Propionate ≡ benzoate and sorbate

SULFUR DIOXIDE AND SULFITES

Forms: SO2, SO3

-2, SO3

-1, S2O5

-2, HSO3-1

Potassium metabisulphite (K2S2O5)

Sodium metabisulphite (Na2S2O5)

K2S2O5(s) → K2SO3(s) + SO2 (g)

SO2gas is mixed with H2O- salts of sulfurous acid is formed

Sulfurous acid

Bisulfite ion

Sulfite ion

Most foods pH 3-7

Most prevalent is bisulfite and little sulfite (IV) ions

Sulfite ion can oxidize

SO32-

+ 1/2 O2 SO4

2-

The reaction is irreversible

It consumes O2and limits the oxidation of other compounds

Free, bound and total forms of SO2

KMS/SMS is more preferable due to food pH 3-6 HSO3-


SO2gas, liquid, acid salts or natural forms:

Dried fruit

Lemon juice

Molasses

Wines

Fruit juicesetc.

Sulfites (SO3

-2) react with food constituents: nucleotides, Sugars, Disulfide bonds etc.

Bisulphite ion (HSO3-1

) andSO2: inhibitbacteria than yeasts and molds

SO2 : Antimicrobial and Antioxidant activity

Bcteriostatic against Acetobacterspp. andLactic acid bacteria at low pH

Control acetic acid producing malolactic bacteria in beverages

The effectiveness is enhanced at low pH

Use for fruit and vegetable dehydration

Prevent non-enzymatic browning of process foods i.e: soup mixtures

SO2 widely used as a preservative in fruit pulps

Pork: SO2 ≥ 100 ppm inhibit the spores of C. botulinum

Sausages: 600 ppm sodium metabisullfiteinhibit the salmonellaespp.

Aerobic are more sensitive than fermentative

Yeasts forms SO2 during fruit juice fermentation

SO2 react with vitamin B1 and Anthocyanin

Antioxidant

SO2protects graph juice and wine from excessive oxidation

SO32-

+ 1/2 O2 SO4

2- (consume O2)

Anti-enzymatic

SO2inhibits oxidation enzymes and destroys them with time

Inhibits the polyphenol oxidase (PPO) oxidative reactions in juice and fresh cut fruits

Taste

SO2 will bind with acetaldehyde: "fresher" aroma in a wine

SO2 increase the extraction of flavonoid phenols(bitterness and astringency)

Fermentation

At low levels SO2 delays the fermentation, but later speeds up the multiplication of yeasts

Color

Wines fermented with SO2: retain color

Excessive amounts of SO2: discoloration of red pigments


Anti-Browning

Enzymatic and Non-enzymatic browning

Enzymatic browning – discoloration of fresh cut surface of fruits and vegetables due to

polyphenol oxidase (PPO) and peroxydase (POD)

Phenol Melanins

SO2 inhibits PPO

Reduces enzymatic browning by obstructing PPO and POD

With KMS

Diphenol

Colorless Colorless

Non-enzymatic browning of process foods due to heating or storage

i. Maillardrection

ii. Caramalization

iii. Ascorbic acid oxidation

Anti-microbial

Low concentrations, SO2 inhibit the development of microorganisms.

High concentrations, destroy microbial population

Mode of action: 1. Lowering the pH of foods

2. Antimicrobial - due to strong reducing power

3. Inhibit the enzymatic browning (drying)

4. Reduction of disulfide bonds (effect on enz.)

5. Reaction with ketone

6. Inhibition of respiratory mechanism

Sulphites have been associated food intolerance symptoms

Headaches

Irritable bowel symptoms

behavior disturbance

Skin rashes

Asthma

Eye Irritation


NITRITES AND NITRATES

KNO3/NaNO3 and KNO2/NaNO2 use for meat curing

agent:

Stabilize red meat color

Flavor development

Secondary effect

Inhibit spoilage and food poisoning MOs

Myoglobin

oxidation + bacteria

Oxymyoglobin Metmyoglobin (-OH)

Metmyoglobin bacteria Choleglobin (-H2O2)

Metmyoglobin bacteria Sulfmyoglobin (-SH)

Metmyoglobin: brown color pigment

Meat Curing

NO2- act as a reducing and oxidizing agent

NO2- acidenv. 3HONO NO

(nitrous acid) (nitric oxide)

NaNO2 + H2O HNO2 + NaOH

NO2 + H2O HNO2 + 2NO + H2O

In acidic solution

3HNO2 HNO3 + 2NO + H2O

NOimportant for color fixation in cured meats

Myoglobin +NO +heat

Oxymyoglobin Nitric oxide myoglobin Nitrosylhemochromogen

NO + myoglobin nitrosomyoglobin (red pigment)

NO2 disappear on both heating and storage

Organisms affected C. botulinum Nitrite has anti-botulinal effects

Inhibition of vegetative cell growth and spores that survive from heat or smoke

C. botulinum, C. butyricum, C. sporogenes, perfringens, S. aureus, Salmonellae spp.

Lactic acid bacteria are resistance to nitrite


Nitrosamines

Nitrite + 2ry

amines => nitrosamines

Many nitrosamines are carcinogenic:

H+

R2NH2 + HONO R2N-NO + H2O

Dimethylamine reacts with nitrite to form N-nitrosodimethylamine

N-H + NO2 N-N= O

Secondary amines, tertiary amines and quaternary ammonium compounds also yields nitrosamines

Nitrosamines exist in cured meat and fish product (at low level)

Isoascorbatehas an inhibitory effect on nitrosamine formation

Therefore, nitrite-sorbate (low level) can be used for curing

Effect of Nitrite and Sorbate on production of toxin in Bacon by C. botulinum (for types A and B) at 27 oC during 60 days

Treatment Toxigenic%

Control 90

0.26% sorbate 58.8

0.26% sorbate + 40 ppm NaNO2 22

0.26% sorbate + 80 ppm NaNO2 00

120 ppm NaNO2 00.4

Mode of Action

Nitrite inhibits bacteria (ie: C. botulinum) by interfering with Fe-S enzymes/ protein thus prevent the synthesis of ATP from pyruvate and leads to an accumulation of pyruvate. In the breakdown of pyruvate:

SALT AND SUGAR

Salt (i.e. NaCl)

Slat (saline) in water at 0.8-0.9% produce isotonic condition for non-marine M.O

Hypertonic condition (high salt conc.) cause plasmolysis of cells

Both Mo and plant/meat tissues undergo plasmolysis result: shrinkage

Drying of meat and inhibit the growth or death of MO

Most non-marine MOs can be inhibited by 20% or less of NaCl

Salt effects are:

1. Causes high osmotic pressure and hence plasmolysis of cells

2. Dehydrates of foods

3. Ionize to yield the Cl-

which is harmful to MO

4. reduces the solubility of O2 in the moisture

5. Sensitizes the cell against CO2

6. Interferes with the action of proteolytic enzymes

CH3 CH3

CH3 CH3


Sugars

Sugars also act as salt

But main differences is in relative concentration

One unit NaCl = 6 units of Sucrose

Sugars uses as preserving agents

e.g: Fruit preserves, Candies, Condensed milk

Yeast and molds less susceptible to sugars than bacteria

Yeast and molds can grow in the presence of 60% sucrose: Osmophiles or Osmoduric

INDIRECT ANTIMICROBIALS

Antioxidants

A molecule that inhibits the oxidation of other molecules

Oxidation can produce free radicals =>chain reactions => damage cells

Antioxidants : i.e: Thiols or ascorbic acid terminate chain reactions

Primarily to prevent the auto-oxidation of lipids

Antioxidants

Phenols (hydroquinone, pyrogallol, etc.)

Natural occurring substances

glutathione, ascorbic acid, vitamin E, etc.

shows antimicrobial activity for wide range of MOs

I.e. Bacteria, fungus, viruses, mycoplasmas and protozoa

High concentrations are required to inhibit MO in high-fat food

Some antioxidants increases the storage life of fats

i.e.: Ascorbic acid, Ascorbyl palmitate, calcium Ascorbate, Erythorbic acid, Sodium ascorbate and

Tocopherols

Oxidation of Fats

Fats and oils in food more prone to oxidation

Antioxidant foods to prevent oxidation

e.g.: vegetable oil, animal fat, meat, fish, poultry, baked products, potato products, margarine, salad

dressing etc.

Antioxidant Vitamins - Ascorbic Acid- E300

Beers

Cut fruits

Dried potatoes

Jams

Biscuits

Alcoholic drinks

Cheese

Dried soup

Preventing the discoloration of food

Increases the anti-oxidant effect of other substances

Regulates pH in jams and jellies

Butylated hydroxyl anisole (BHA) - E320

Butylated hydroxyl toluene (BHT)

https://en.wikipedia.org/wiki/Chain_reaction


Margarine, oils, crisps and cheese, cereals, gum, fast food, processed potatoes, drink mixes, shortening,

snack foods etc.

High concentration toxic to liver and CNS

Tocopherols (E306) – 0.1% for fat and oil

less volatile than BHA and BHT

Meat and oils to reduce the oxidation of fatty acids and vitamins

Compounds are also found in food packaging, animal feeds, cosmetics, pharmaceuticals, rubber, and

plastics

SPICES AND ESSENTIAL OILS

According FAD:

spice is an “aromatic vegetable substance in the whole, broken, or ground form, the significant function of which

in food is seasoning rather than nutrition” and from which “no portion of any volatile oil or other flavoring

principle has been removed”

Asia

Cinnamon, pepper, nutmeg, cloves, ginger etc.

Europe:

Basil, bay leaves, celery leaves, chives, coriander, dill tips, thyme, and watercress

America:

Allspice, and sesame seed

Spices possess significant antioxidant and antimicrobial activity due to chemicals and essential oils

Antioxidant property

I. scavenging free radicals

II. chelating transition metals

III. quenching singlet oxygen

IV. enhancing antioxidant enzymes activities

ginger extract = activity of BHT in inhibiting the lipid peroxidation

Black pepper extracts reduced the formation of acrylamide up to 75%

Inhibitory effect of spices differs with kind of spice and the type MO

Difficult to ascertain minimal inhibitory concentration (MIC)

Effectiveness depends on the source and process etc.

Growth of Aspergillus spp. was inhibited by 200-300 ppm of cinnamon and clove oils, 150 ppm of cinnamic

aldehyde and 125 ppm of eugenol.

A. flavus (Aflatoxin) can be inhibited ginger essential oil

Cinnamon and cloves are more effective against bacteria

Mustard flour and EOs are very effective against yeast

Mode of action is not completely understood

http://chemistry.about.com/od/foodcookingchemistry/a/bha-bht-preservatives.htm

http://www.ncbi.nlm.nih.gov/pubmed/3583158


FATTY ACIDS AND ESTERS

Propionic and sorbic acids are short-chain fatty acids use as preservatives.

Medium-chain FA are used as surface active or emulsifying agents

Most common compounds C12 to C16

For saturated antimicrobial FA chain length is C12,

Antimicrobial activity monounsaturated is C16:1 and for polyunsaturated is C 18:2

preservative effects increases with double bonds

C12 – C16 are effective against bacteria

C10 to C12 are effective against yeasts

FA have specific odors: may lower the acceptability of the food

OTHER ACIDS

Lactic acid

Most widely employed organic acids (OA) as preservatives

Produce in the food by fermentation: acetic, lactic and other acids

i.e: pickles, sauerkraut, fermented milk etc.

Antimicrobial effects due to both:

1. Depression of pH

2. Metabolic inhibition by undissociated molecules

OA are used to wash and sanitize the animal carcasses after slaughter to reduce their pathogens and increase

shelf-life

FOOD “ANTIBIOTICS” OR BACTERIOCIN

Secondary metabolites produced by MO that inhibit or kill other MO

Most useful ones are produced by Streptomyces spp.

Some antibiotic-like substances are produced by Bacillus spp.

ie.:Nisinby Lactococcuslactis

It is a rare AA - form anti-bacterial peptide or protein best known as a bacteriocin

Bacteriocins inhibitor kill only closely related species or strains of the same species

Lactic acid bacteria produce bacteriocin is lantibiotics


Tow antibiotics are used in food industry:

Nisin and Natamycin

Another 3 have been found effective: Tetracyclines, Subtilin and Tylosin

Nisin is used in cheese industry

For canned foods: Subtilin, Tylosin and Nisin

For fresh foods: Chlortetracycline and Oxytetracycline

Nactamycin used as food fungistat

Application of antibiotics in foods is somewhat slower than medicine

CONSIDERATION OF ANTIBIOTICS AS FOOD PRESERVATIVES

The antibiotic should kill the flora but not inhibit

Residue should be;

decompose into innocuous product

destroyed on cooking

The antibiotic should not be inactivated b;

food components

products of microbial metabolism

The antibiotic should not stimulate the appearance of resistant strains

The antibiotic should not be used in food if it is used;

therapeutically

as an animal feed additives

i.e:

Tetracyclines- clinically and as feed additives

Tylosin- feed poultry diseases with feeds

Nisin

It is a polypeptide agent, widely used antibiotic for food preservation

Prevent the spoilage of Swiss cheese from C. butyricum

Desirable properties

1. Nontoxic

2. Produced naturally by Lactococcuslactis strain

3. Heat stable and excellent storage stability

4. Destroyed by digestive system

5. No off-flavor or off-odors

6. Narrow spectrum of antimicrobial activity

Effective agents gram+ bacteria

Ineffective against fungi and gram- bacteria

Fo value reduces significantly by adding nisin to low acid canned food

Mode of action: depolarize energized cytoplasmic membrane

Mode of action:

Binding to sterolsin cell membrane and distorting of selective membrane permeability

Sterols not found in bacterial cell wall


GASEOUS STERILANT

Ethylene and Propylene Oxides

Both have similar action

Employed as fumigants in the food industry, primarily as antifungal compounds

Ethylene Oxide Propylene oxide Ethylene oxides (EO)is heat labile sterilize substances

EO is an alkylating agent

EO readily reacts compounds with opening of the ring

Acidic : weak nucleophiles reactions with water, alcohols

EO is a gaseous sterilant for flexible and semi-rigid containers

Aseptically processed foods and warehouses

Dried fruits

Eggs

Gelatin

Cereals

Dried yeast

Spices

Gums

Starchs

Coco

Disinfectant effect of EO = Sterilization by heat

Limited penetration

Affects only on the surface

Propylene oxide is permitted as a package fumigant and for dried fruits

PH3


Formaldehyde

Formaldehyde is used as a fumigant

It has been almost abandoned

.

Ozone

Sterilizes by strong oxidation

Destroysall organic and inorganic matter

Surface sterilization fruits, vegetable and dry commodities

Phosphine Fumigation (PH3)

Hydrogen phosphide (PH3) is a low molecular weight

Phosphide contact with moisture and forms PH3 gas

AlP + 3H2O => PH3(g) + Al(OH)3

Mg3P2 + 6H2O => 2PH3(g) + 3Mg(OH)2

Kill all types of stored products insects (egg-larva-pupa-adults)

Fungal static

WOOD SMOKE

Wood smoke contains formaldehyde and other organic volatile preservatives

Pyrolysis wood smoke contains many other anti-microbial compounds

Heat reduce MOs and somewhat dries the food

Improve the color and flavor of meat

Use soft woods for smoke

Smoke contain Polyaromatic hydrocarbons (PAHs) are carcinogens

Now use liquid smoke

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BENZOIC ACID C6H5COOH or C7H5NaO2 p