The Basics of Food Procesing and Preservation

7/23/2019 The Basics of Food Procesing and Preservation

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THE BASICS OF FOOD

PROCESING AND

PRESERVATION

I MADE SUPARTHA UTAMA

MATERIAL II


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OUTLINES

SMOKING

FERMENTATION

SALTING

SIZE REDUCTION

EXTRACTION

MODIFIED ATMOSPHERE


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SMOKING

Meat, fish and some other foods may be

both preserved and flavoured through

the use of smoke, typically in a smoke-

house. The combination of heat to dry the food

without cooking it, and the addition of

the aromatic hydrocarbons from thesmoke preserves the food.


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SMOKING

Desirable Effects of Smoking

Brings out the color inside cured meats.

Impregnates the outside of the meat with constituents of the smokethat serve as antiseptics and germicides.

Imparts desirable organoleptic properties.

Causes a tenderizing action which results from increased activity ofenzymes if the meat temperature is elevated above 60F (16C).

Causes a tenderizing action that results from the meat beingexposed to high temperatures and high humidities in thesmokehouse.

Imparts antioxidants to the fats. Has a destructive action on microorganisms when the smokehouse

temperature is above 120F (49C).

Imparts a desirable finish or gloss.

Reduces the nitrite content.


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Contents of Smoke

Hardwood smoke will yield the following range

of concentration in the Smokehouse:

Formaldehyde, 25 to 40 ppm.

Phenols, 20 to 30 ppm.

Formic acid, 90 to 125 ppm.

Higher aldehydes, 140 to 180 ppm.

Ketones, 190 to 200 ppm.Acetic and higher acids, 460 to 500 ppm.

Resins, over 1,000 ppm.


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The Incubation Zone Mesophilic bacteria will grow during the

incubation period or zone, which is 65 to105F (18 to 41C).

The tendency is for the bacteria count toincrease during this period; however, thetotal count will be considerably reduced atthe end of the smoking period.

A good smoking practice is not to hold theproduct in this zone for more than 6 to 8hours.


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The Residual Effect.

The residual effect of the smoke on

bacteria is very pronounced.

Most smoked cured products will keep

considerably longer than unsmoked

cured products.

The residual effect of smoke againstmolds is much less than the effect

against bacteria.


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FERMENTATION

Fermented foods are among the oldest processed foodsand have formed a traditional part of the diet in almost allcountries for millennia.

Today they continue to form major sectors of the foodprocessing industry, including baked products, alcoholic

drinks, yoghurt, cheese and soy products among manyothers.

During food fermentations, the controlled action ofselected micro-organisms is used to alter the texture offoods, preserve foods by production of acids or alcohol, orto produce subtle flavours and aromas which increase the

quality and value of raw materials. Today the preservative effect is supplemented by other

unit operations (for example pasteurisation, chilling ormodified atmosphere packaging


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The main advantages of

fermentation the use of mild conditions of pH and

temperature which maintain (and oftenimprove) the nutritional properties andsensory characteristics of the food the

production of foods which have flavours ortextures that cannot be achieved by othermethods

low energy consumption due to the mildoperating conditions

relatively low capital and operating costs

relatively simple technologies.


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The main factors controling the growth

and activity of micro-rganisms in food

fermentations are:

availability of carbon and nitrogen sources, andany specific nutrients required by individualmicro-organisms

substrate pH

moisture content

incubation temperature

redox potential stage of growth of micro-organisms

presence of other competing micro-organisms.


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Types of food fermentations

Micro-organisms that produce a single main by-product are termed homofermentative, whereasthose that produce mixed products areheterofermentative.

Fermentations can be classified into those in which

the main products are organic acids and those inwhich ethanol and carbon dioxide are the primaryproducts.

Lactic acid and ethanolic fermentations are amongthe most important commercial fermentations

Many fermentations involve complex mixtures ofmicroorganisms or sequences of microbialpopulations which develop as changes take place inthe pH, redox potential or substrate availability.


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Salting

Salt is one of our oldest preservatives andis still a widely used preservative.

Salt in concentrations in which it isnormally used in preservation is not a

bactericide, but rather inhibits manyspecies of bacteria.

Salt exerts its preservative action bydehydration, direct effect of the chloride

ion, removal of oxygen from the medium,sensitization of the organisms to carbondioxide, and interference with rapid actionof proteolytic enzymes.


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The Brine Concentration Formula.

The effectiveness of salt is based upon the amountof moisture in the tissues.

The ratio of salt to water is expressed as brineconcentration.

The brine concentration is arrived at by dividing thepercentage of salt by the sum of the salt plus themoisture.

This figure is then multiplied by 100. Luncheon meatcontaining 3.5 percent salt and 59 percent moisturewould have a brine concentration of 5.60 percent.

Dried beef containing 50 percent moisture and 3.5percent salt would have a brine concentration of 6.54percent.


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Requirement Vary

cooked pork may require only five percent salt to inhibit

the production of toxin by Clostridium botulinumorganisms, whereas ten percent salt might be required forthe same inhibitory action in dextrose broth.

It has been observed that in different media of the samemoisture content, there may be more salt required toprevent the formation of Clostridium botulinum toxin inone than in the other.

The Clostridium botulinum organism is commonly found incanned meat products and cured meat products.

There will normally be sufficient salt present to keep theClostridium botulinum organisms in a spore-forming state,

so that there will be no toxin produced.

There must always be sufficient acid or salt to keep theClostridium botulinum organisms in a spore-forming state.


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Salt Loving Organisms

There is a group of bacteria classified ashalophiles ("salt loving") that will grow inthe presence of high concentration of salt.

Some of these organisms will even grow in

a saturated (26 percent) or supersaturatedsalt solution.

Bacteria that will grow in a saltconcentration of tenpercent or higher are

classified as halophiles. There are also many varieties of yeast and

mold that will grow in a salt concentrationabove ten percent


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SIZE REDUCTION

Many food processes frequently require the reduction in size ofsolid materials for

different purposes.

For example, size reduction may aid other processes, such asextraction, or may shorten heat treatments, as in blanching andcooking.

Comminution is the generic term used for size reduction andincludes different operations such as crushing, grinding, milling,mincing, and dicing. Most of these terms are related to aparticular application, for example, milling of cereals, mincing ofbeef, dicing of tubers, or grinding of spices.

The reduction mechanism deforms the piece of food until it

breaks or tears. Breaking of hard materials along cracks or defects in their

structure is achieved by applying diverse forces.

The types of forces commonly used in food processes areompressive, impact, attrition or shear, and cutting


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Benefit of Size Reduction

An increase in the surface-area-to-volume ratio ofthe food which increases the rate of drying, heatingor cooling and improves the efficiency and rate ofextraction of liquid components (for example fruitjuice or cooking oil extraction).

When combined with screening, a predeterminedrange of particle sizes is produced which is importantfor the correct functional or processing properties ofsome products (for example icing sugar, spices andcornstarch).

A similar range of particle sizes allows morecomplete mixing of ingredients (for example driedsoup and cake mixes)


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Different methods of size

reduction Chopping, cutting, slicing and dicing:

(a) large to medium (stewing steak, heese and sliced fruitfor canning)

(b) medium to small (bacon, sliced green beans and dicedcarrot)

c) small to granular (minced or shredded meat, flaked fishor nuts and shredded vegetables).

Milling to powders or pastes of increasing fineness(grated products > spices > flours > fruit nectars >powdered sugar > starches > smooth pastes)

Emulsification and homogenisation (mayonnaise,milk, essential oils, butter, ice cream and margarine)


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EXTRACTION

One area in food processing that is receiving increasing attention is extraction.

This separation process involves two phases. The solvent is the material added

to form a phase different from that where the material to be separated originally

was present.

Separation is achieved when the compound to be separated dissolves in the

solvent while the rest of the components remain where they were originally.

The two phases may be solid and liquid, immiscible liquid phases, or solid and

gas. Solidl iquid extraction is also called leaching.

Oil from soybean, corn, and rice bran cannot be separated by mechanical

pressing, therefore, solvent extraction is used for their recovery.

Oil from peanuts is recovered by mechanical pressing and extraction of the

pressed cake to completely remove the oil.

One characteristic of solvent extracted oilseed meal is the high quality of the

residual protein, suitable for further processing into food-grade powders.

They may also be texturized for use as food protein extenders.


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Solid-Liquid Extraction Leaching)

This is a separation operation in which thedesired component, the solute, in a solidphase is separated by contacting the solid witha liquid, the solvent, in which the desired

component is soluble. The desired component leaches from the solid

into the solvent. Thus the compositions of boththe solid and liquid phases change.

The solid and liquid phases are subsequentlyseparated and the desired componentrecovered from the liquid phase.


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TYPES OF EXTRACTION PROCESSES

Single-Stage Batch Processing In this process, the solid is contacted with solute-free

solvent until equilibrium is reached. After equilibrium,

the solvent phase is drained out of the solids.

Multistage Cross-Flow Extraction

In this process, the solid is contacted repeatedly,

each time with solute free solvent. This procedure

requires a lot of solvent, or in the case of a

soxhlet, a lot of energy is used in vaporizing and

condensing the solvent for recycling, therefore, it

is not used as in industrial separation process.


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Multistage Countercurrent

Extraction

This process utilizes a battery of extractors. Solute-free solvent enters thesystem at the opposite end from the point of entry of the unextracted solids.

The solute-free solvent contacts the solids in the last extraction stage, resulting inthe least concentration of solute in the solvent phase at equilibrium at this lastextraction stage.

Thus, the solute carried over by the solids after separation from the solventphase at this stage is minimal.

Solute-rich solvent, called the extract,merges from the system at the firstextraction stage after contacting the solids that had just entered the system.

Stage to stage flow of solvent moves in a direction countercurrent to that of thesolids.

The same solvent is used from stage to stage, therefore solute concentration inthe solvent phase increases as the solvent moves from one stage to the next,while the solute concentration in the solids decreases as the solids move in theopposite direction.

A good example of a multistage countercurrent extraction process is oil extractionfrom soybeans using a carousel extractor. This system called the rotocell is nowin the public domain and can be obtained from a number of foreign equipmentmanufacturers.


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MODIFIED ATMOSPHERE

Modified atmosphere is a way to preserve food by operating on theatmosphere around it. Salad crops which are notoriously difficult topreserve are now being packaged in sealed bags with an atmospheremodified to reduce the oxygen (O2) concentration and increase thecarbon dioxide (CO2) concentration. There is concern that althoughsalad vegetables retain their appearance and texture in suchconditions, this method of preservation may not retain nutrients,

especially vitamins. Grains may be preserved using carbon dioxide. Ablock of dry ice is placed in the bottom and the can is filled with grain.The can is then "burped" of excess gas. The carbon dioxide from thesublimation of the dry ice prevents insects, mold, and oxidation fromdamaging the grain. Grain stored in this way can remain edible for fiveyears. Nitrogen gas (N2) at concentrations of 98% or higher is alsoused effectively to kill insects in grain through hypoxia. However,carbon dioxide has an advantage in this respect as it kills organisms

through both hypoxia and hypercarbia, requiring concentrations of only80%, or so. This makes carbon dioxide preferable for fumigation insituations where an hermetic seal cannot be maintained.
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The Basics of Food Procesing and Preservation

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