Coffee and its processing

Coffee Processing

•  Roasting process

It is a time-temperature dependent process, whereby chemical changes are induced by pyrolysis within the coffee beans, together with marked physical changes in their internal structure. The required change takes place with a bean temperature from 190°C upwards; bean temperature up to 240°C may be reached in less than 12 minutes.

Batch operated horizontal rotating drum roaster with either solid or perforated walls, in which hot air from a furnace/burner passes through the tumbling green coffee beans. Green coffee beans under movement are subjected to heat by conduction from hot metal surfaces, or convection from hot air, or more generally a mixture of both methods of heat transfer, together with a contribution by radiation.

A typically sized roaster holds 240 kg of green coffee, with an outturn (charging to discharging) of 15 min. The furnace or burner will be either oil or gas-fired.

Other roasters include:

•       Vertical static drum with blades
•     Vertical rotating bowl
•        Fluidized bed
•        Pressure roasting

The latest roasters have shorter roast times i.e. of the order of 3-5 min. Fast-roasted coffee is advantageous because of lower bulk density and high yield on brewing.

The degree of roast may vary from Very light to very dark.

Consumer preference is usually medium roast.

Physico-chemical changes in coffee

• Chemical Changes 

The chemical changes include Maillard type reactions and caramelization of sucrose. The composition of roasted coffee is furnished below table

The volatile complex comprising of furan derivatives, pyrazines, pyridines, benzenoid aromatics, aliphatics, alicyclic and various sulphur compounds. These are important for the flavour/aroma in medium-roast Arabica coffee.

Some compounds are generated by straight pyrolysis of single compounds e.g. chlorogenic acids in generating phenols; there is an overall 40% residual content for a medium roast. The change in chlorogenic acid content is used as an analytical measure of the degree of roast.

Similarly, coffee oil leads to the formation of small amounts of aldehydes and hydrocarbons. The coffee oil is practically unaffected, as is the caffeine content.

The newly formed residuum of ~ 25% by weight of roasted coffee is melanoidins/humic acids. The loss of mass is 2-3% on a dry basis for Light roast, whereas it is up to 12% on a dry basis for a Very dark roast. The beans lose 15-20% of their weight but increase up to 25% in size.

• Physical changes

The physical changes that occur include:

•        Change in colour.
•        Formation of cavities/cracking of the surface.
•       Void volume is 47% of medium roast bean vs. 0% in the green bean.

• Cooling

In batch operation, the roasted beans have to be quickly discharged at the end of the required roasting period into a cooling car, or vessel, allowing upward passage of cold air.

Also, water may be sprayed from within the rotating drum, just before the end of the roast so-called Water quenching.

Advantages of water quenching

1.   Assists in necessary cooling.
2.  Adds a small percentage of water by weight to roasted beans, thereby assists uniformity of particle size in subsequent grinding.

 Composition of roasted coffee 

Component	Typical average content for (%)
	Arabica	Robusta
Alkaloids (caffeine)	1.3	2.4
Trigonelline (including roasted byproducts)	1.0	0.7
Proteinaceous     Protein      Free amino acids	7.5 0	7.5 0
Lipids (Coffee oil with unsaponifiable)	17.0	11.0
Sugars:     Sucrose     Reducing sugars	0 0.3	0 0.3
Polysaccharides (unchanged from green)	33.0	37.0
Lignin	3.0	3.0
Pectins	2.0	2.0
Acids     Residual chlorogenic     Quinic     Aliphatic	2.5 0.8 1.6	3.8 1.0 1.6
Minerals (oxide ash)	4.5	4.7
Caramelized/condensation products (Melanoidins, etc.)	25.5	25.5
Total	100.0	100.0

 Grinding

Multistage twin horizontal rollers up to 4 stages may be used to ensure more uniform particle size distribution.

1^st and 2^nd stages  Essentially perform cracking or crushing the beans into smaller units.

3^rd and 4^th stages Lead to progressively finer grinding.

The grind size required is related to the subsequent method of brewing to be adopted and whether for home use or subsequent large scale extraction i.e. coarse, medium, fine, very fine. The ground size of roasted and ground coffee beans for different applications is presented below

                                                   Grind size of roasted and ground coffee beans

 

Grind size	Actual size (m)
Fine grind	430 (Europe), 800 (USA)
Coarse grind*	850 (Europe), 1130 (USA)

* for household percolators

The number of different screen sizes numbered by aperture size within the range of 1400 m to 250 m. The newer method performs sizing by laser beams.

Packaging

Roasted and ground (R & G) coffee releases substantial quantities of entrapped CO₂ gas which develops high internal pressure, leading to the bursting of package.

The usual packaging material is laminated.

Packaging under vacuum

It allows a low percentage of oxygen content in the headspace to be established within the package and accommodate the release of CO₂. Alternatively, CO₂ scavenger may be used.

Degas over a sufficient time period

The R & G coffee is allowed in bulk to degas over a sufficient time period to a low level, followed by gas purging whilst individual packages are being filled.

Gas purging is used to ensure that the residual oxygen in the headspace is below 1.0%.

In Europe, the use of plastic packages to which a non-return valve is securely attached allows the release of excess CO_2, when the internal pressure exceeds a certain predetermined level.

A Glance at the Processing Steps

 Green bean treatment

       Cleaning

       Blending

       Storage

   Roasting

 Roast bean treatment

       Storage

       Grinding

       Conditioning

 Extraction

       Fast instant coffee extractors (FIC)

       Conventional batch percolators

       Continuous counter-current extractors (CONTEX)

      FIC extraction unit

It reduces extraction time by 50% compared to batch percolators. Water is directed through the ground coffee in two stages. The process results in two completely separated extract fractions viz., aroma and hydrolysis. After extraction, the extract is filtered and centrifuged.

  Extraction treatment

       Aroma recovery

       Clarification

       Clarification

It is a system consisting of filters and centrifuges to separate insoluble parts from the extract to achieve international standards.

 Concentration

       Falling film and plate evaporators

      Freeze concentration

       Membrane filtration systems

       Concentration: It serves to increase the solids content in extract before freeze or spray drying.

a)      Thermal concentration  Multistage non-recirculating evaporators operating under vacuum in a plug flow model.

b)     Membrane filtration The aroma fraction of the extract can be pre-concentrated using reverse osmosis in a membrane filtration system.

c)      Freeze concentration  By cooling the extract to subzero temperatures, excess water is removed as ice crystals.

Freeze and thermal concentration, membrane filtration, Falling film and plate evaporators are used for the purpose of concentration.

  Drying

       Nozzle Tower spray dryer

       Fluidized bed spray dryer

       Continuous freeze dryers (CONRAD)

       Batch freeze dryers (RAY)

  Agglomeration

       Rewet agglomerators (RWA)

  Packing

  Domestic and Catering Methods of Brewing

Brewing is the extraction of soluble substances contributing to the basic taste plus of volatile substances for overall flavour. Roast coffee must be ground before brewing.

The two main mechanical principles are:

 Steeping/ Slurrying of R & G coffee with water, with or without agitation, followed by sedimentation or filtration or both.

     Percolation in fixed beds of R & G coffee held in an open or closed container. Water may be passed through either in a single pass under gravity or under pressure (including steam, as in Espresso making), or in a multipass.

    Extraction

Extraction of coffee solids can be carried out by

          Fast instant coffee extraction.

          Conventional batch percolators.

         Continuous countercurrent extractors.

  Factors in Brewing

          Coffee-to-water weight ratio

          The appliance used for brewing.

          The temperature employed.

Of the components of roasted coffee, only some will be extracted completely with variable amounts of the others to reach ~ 28% w/w total maximum and 21% optimum under household brewing conditions, by hot or boiling water so-called yield.

The mechanical operation involved is a means of separating the undesired so-called Spent coffee grounds from the required brew formed by sufficient contact with water. The brew should contain as little of spent ground particles as possible and must be presented hot (i.e. 50-55°C).

  Flavour Quality of Coffee Brew

The factors determining the flavour quality of brew include:

       The choice of blend used.

       The degree of roast.

       Brewing conditions.

       Choice of grind.

 Filter coffee

South Indian Coffee, also known as Filter Coffee is a sweet milky coffee made from dark roasted coffee beans (70-80%) and chicory (20-30%), especially popular in the southern states of Tamil Nadu and Karnataka. The most commonly used coffee beans are Arabica and Robusta.

Outside India, a coffee drink prepared using a filter may be known as Filter Coffee or as Drip Coffee as the water passes through the grounds solely by gravity and not under pressure or in longer-term contact.

 Aromatization of Coffee

It is a term applied to a process, whereby essentially the headspace coffee aroma volatiles are made available by plating coffee aroma oil, prepared by expression methods from roast coffee, or other sources onto the soluble coffee, usually at the packing stage. This is a treatment imparted to improve the flavour and aroma. The powder lacks full flavour and aroma of freshly brewed coffee. The flavour and aroma constituents are trapped and recovered during roasting, grinding and extraction and from oils pressed from the coffee bean. The cold CO₂ does not damage the flavour and aroma compounds in coffee oil and it is easily separated from extracted oil for recompression and reuse.

After CO₂ removal of the oil, the Roasted and Ground coffee is still highly suitable for extraction of water-soluble solids in the regular extraction battery operation.

 Aroma recovery

The extract fractions are stripped of their volatiles in an aroma recovery unit. After being stripped from the concentrate in a flash evaporator, the aroma is recovered in a 2-stage condenser system. 

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Processing of butter - How it is made?

Butter- 

Fat separated from the cream 

1. Butter may be defined as a fat concentrate which is obtained by churning cream gathering the cat into a compact mass and then working on it.
2. According to PFA rule, there are certain specification for butter, 

• It should be free of animal fat, wax, mineral oil and vegetable oil. 
• There should be no preservative except salt (NaCl).
• Should not contain less than 80% fat.
• Not more than 1.5% curd. 
• Also NaCl not be used more than 3%.
• Diacetyl may be added but not more than 4 ppm, which gives the typical flavour. 
• In butter, some of the alkalines are added - Calcium Hydroxide, Sodium Bicarbonate.  

Various kind of butter -

1. Pasteurize cream butter
2. Ripened cream butter
3. Unripened cream butter
4. Salted butter
5. Unsalted butter
6. Sweet cream butter
7. Sour cream butter
8. Fresh butter
9. Cold storage butter
10. Dairy butter
11. Creamy butter

The standard composition of butter 

Butterfat - 80.2%

Moisture - 16.3%

Salt - 2.5%

Curd - 1% 

Fat-soluble vitamins - Vit- A, D & K

Method of Manufacturing 

Important points- 

1. Grading of cream based on the quality of cream- 

• 1-grade cream is sweet cream and slightly sour.
• 2-grade cream is sour and coagulated. 
• 3-grade cream is rejected, quite fermented.

    2. Testing - cream is tested for fat, SNF and acidity. 

    3. Preheating - to increase the efficiency of the operation. 

    4. Ripening - Addition of starter culture for fermentation, to enhance the flavour and lesser fat loss in the serum. It is ripened by the starter culture that is streptococcus lactis and Streptococcus cremoris. Some more microorganisms are known as aroma producer- 

• Streptococcus diacetylactis
• Leuconostoc citrovorum
• Leuconostoc dextranium

1. These microorganisms produce diacetyl which gives the typical aroma.
2. Inoculated at 21°C for 15-16 hours.
3. Acetic acid or propionic acid also gives some flavour.
4. Set range for standard diacetyl content is 0.2 to 0.6 ppm gives a mild flavour to butter.
5. More than 2.55 ppm and 4 ppm rise in butter could be rejected. 
6. Mother substance from which diacetyl is produced are acetyl, methyl and sometimes citric acid is added before fermentation.  

Churning - 

Separation of fat from cream. Agitation of cream at a suitable temperature until the fat globule adheres to forming a larger and larger masses until the complete separation of fat and serum occur.

• Cream in a form of emulsion - stable in nature
• fat - skim milk emulsion 
• churning breaking out the stability of fat and milk 

Force for making stable

Surface Tension - 

- Cream and fat globule retain their individuality

- Prevent butter formation 

Phenomena of adsorption - 

- Fat globule in milk or cream, they are in a layer which is phospholipid layer. 

- This membrane resists de - emulsification 

- Adsorb at the surface of fat globule

- They make the charge stabilize. 

Electric Charge - 

- Fat globules are negatively charged. 

- result all of them repel each other.

Viscosity - 

- higher the viscosity more stable is an emulsion 

- Resist Churning 

During the churning, the temperature is above the melting point of the fat 31-38°C. Agitation results in the subdivision of fat and serum.

Churning operation - 

1. It starts with the preparing of churning by cleaning, sanitization and deals with all the types of pre-treatment.
2. Filling cream into the churn, slightly above the capacity. 
3. Addition of butter colour- carotene and annatto, 250 ml of colour is added to 100 kg of butter. 
4. Operation of churning - 

• Initial rotation (5-10 times)
• liberate any gas present in the cream. 
• the rise in temperature of 1-3 °C of the cream
• Foaming
• addition of water to lower the temperature
• after the foaming, breaking stage occurs when the cream breaks away, the formation of butter grains of pea-size.
• Churning is stooped and fat is collected
• washing of butter - to remove every adhering particle of serum or buttermilk.

The procedure of washing - 

Buttermilk is drained, then water is added to butter which has the temperature 1-2 °C lower than churned butter, the amount is equal to the amount of buttermilk separated from fat. Then churned is again switched on after few rotations then water is drained out. Washing is followed by salting and working (kneading of butter)

Reason for adding salt - 

• To improve the keeping quality 
• to enhance the taste 
• to increase the overrun 
• Salt must not be exceeded to 2-2.5%, maximum 3%. 

The objective of kneading or working - 

1. To complete dissolve, uniformly distribution and properly incorporate the salt. 
   To expel the buttermilk and to control the moisture content of the butter.
2. To bring the butter raise together into the compact mass, convenient to handling and packaging.

Packaging of butter - 

Packaging material for butter should have excellent barrier properties such as

· It should be moisture-proof

· It should be greaseproof

· It should be impervious to light

· It should have good strength (to prevent tampering during transportation etc.).

Some of the packaging materials used for butter packaging are

i) Parchment paper – also known as butter paper.

ii) wax-coated paper

iii) cellophane

iv) cardboard boxes and teak wood drums lined with food-grade plastic

v) Aluminium foil laminates

vi) Lacquered tin cans (it is costly but is advantageous in tropical countries and prevents de-shaping during storage and transportation.)

Techniques of packaging

1. Manual moulding and wrapping

2. Mechanical moulding and hand wrapping

3. Fully automatic units which mechanically moulds, patts and wraps. It reduces labour cost, handling losses and is suitable for large scale operation. The machine can be reset for different size viz. 10, 15, 100, 250 and 500g. Some of the well-known brands of fully automatic butter packaging machines are Kustner, Benhill (both are German) and SIG (Swiss). In these machines, after wrapping, the pat goes to carton machine for packing in card boxes and transferred to cold storages (5°C) for 24-48 h and then shifted to low-temperature storage (-23 to -29°C).

Storage of Butter

For the sake of consistency and appearance, butter should be placed in cold store as soon as possible after wrapping and should be chilled to 4°C for 24 to 48 h. Unless this is done, fat crystallization is very gradual and the butter retains its freshly churned consistency and appearance for several days. However, once it has been sufficiently chilled, a subsequent rise in temperature will not make it as soft as it would have been at the same temperature prior to its chilling. The initial freshly churned, somewhat ointment like consistency is transformed to that typical for butter. This change is known as the setting of butter. The butter cannot be considered finished until it has been chilled or set. A low storage temperature also improves its keeping quality and reduces the risk of the package being deformed.

As butter is essentially a perishable product it should not be stored longer than necessary. However, when production exceeds demand and also quite often to level out the fluctuation between high flush season production and low summer production, storage of butter becomes unavoidable. For a short period, butter can be stored at about 4°C but if longer storage is involved it must be deep-frozen at -23°C and only best quality butter should be selected for deep freezing. Since the solubility of salt is low (35.7% at 0°C), some salt crystallization may occur during storage but the crystals re-dissolve on thawing.

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Production of Beer

From barley to beer the production of beer is known as Brewing.

There are top-fermented beer and bottom-fermented beer.

• Top fermented beer - also known as ale, are prepared with Saccharomyces cerevisiae, top-fermenting is the oldest method and the yeast used for it. The yeast is applied to the top of the wort, and at a higher temperature.

• Bottom fermented beer - are known as lager beer is bottom-fermented, meaning the yeast works at the bottom of the wort, at a much lower temperature. And that’s because the yeast involved in bottom-fermenting is a hybrid of Saccharomyces cerevisiae and yeast called Saccharomyces eubayanus, wild yeast from Patagonia that likely hitched a ride to Europe on an exchange transport a couple of hundreds of years prior. In contrast to S. cerevisiae, S. eubayanus can flourish in a lot colder temperatures—and their infant yeast, S. pastorianus, acquired that capacity (thanks mother!).

RAW MATERIALS FOR BREWING- 

1. CEREAL GRAINS ( usually barley, corn, or rice) 
2. ADJUNCTS - Starchy material that is added to with the intention of cutting costs, but sometimes also to create an additional feature, such as better foam retention, flavors, or nutritional value or additives. Both solid and liquid adjuncts are commonly used.
3. YEAST CULTURE 
4. HOPS - the cone-shaped flowers of the female hops plant, aka Humulus lupulus. The addition of hops has several effects like - it provides bitterness, it provides pleasantly aroma, provides colloidal stability & foam head retention of a beer, also contains tannins that help precipitate protein during the boiling of wort, and if the protein is not removed then it causes a haze in the beer at low temperature.
5. WATER - mineral, pH, ions - It affects the pH of the beer, which affects how the beer flavors are expressed to your palate; it provides “seasoning” from the sulfate-to-chloride ratio, and it can cause off-flavors from chlorine or contaminants.

Different steps of the brewing process - 

Malting -  

It is done to double up the amylase and proteases in barley grain, these enzymes reproduce in germinated barley that enables it to breakdown carbohydrates and proteins in the grain. In this process grain is cleaned, steeped, or soaked in cold water is done at 10-15 °C for 2-3 days. Then it is drained off and transfer to the malting floor then germination takes place. Sometimes moist warm air is blown through the bed of seedling and water is sprinkled. Gibberellic acid is added to the grain, it is a hormone and fasten up germination. This process is known as malting.

Cleaning and milling of malt - 

Malt is clean and passed over the magnet to remove pieces of the metals, it is milled and this milling is done to expose particles of malt to the hydraulic malt enzyme in the further mashing process.

Mashing - 

This is the central part of brewing done to extract a soluble portion of malt and to enzymatically hydrolyzed the insoluble portion of malt. The malt is crushed using iron rollers and transferred to the mash tank (or "tun"). This tank is a large copper or stainless steel vessel that mixes the malt with warm water until it is of porridge-like consistency. This mixture is called mash. After mixing with similarly prepared cereal grains, the temperature of the mash is raised incrementally from 100-170°F (38-77°C) so that the enzymes react. The enzymes break down the starch in the grain and convert it to simple sugars. Later, the yeast will convert the sugars into alcohol. Once complete, the mash is allowed to sit undisturbed so the solids can descend to the bottom of the tank.

The aqueous solution resulting from the mashing process is known as Wort (liquid part).

Mashing is affected by the combination of temperature, pH, and concentration of wort. If the temperature is between 60-65°C for a longer period then maltose occurs much because the β- amylase activity increase, if the temperature is 70°C for a longer period then dextrin increases which are not utilized by yeast. There are two enzymes involve α- amylase (70°C and ph 5.8) whereas β- amylase (65°C and pH 5.4), proteases (60°C and pH 5.2-5.5). 

Mash Separation - 

At the end of the mashing husk and insoluble material are removed from the wort in two steps- 

1. Wort is separated from solid.
2. Solids are freed from extractable material while washing or sponging with hot water (80°C) and the leftover malt and adjuncts after the mash has extracted are known as spent grain.

Wort Boiling - 

The wort is boiled for one and a half hours in a brew kettle made up of copper or stainless steel. Sometimes adjuncts are also added, corn syrup, sucrose is added initially in the boiling. Hops are also added before and some at the end of the boiling. The main purpose is to - 

1. Concentrate the wort
2. To sterilize
3. to inactivate any enzyme
4. to precipitate complex with tannins
5. to develop color
6. to remove volatile compounds like fatty acids.

Pre fermentation of wort

In this process, derived hops are used is removed in hop strained and during the boiling protein and tannins are precipitate and more precipitating takes place when it is cooled about 50°C.

Precipitate removed by centrifugation. Separated wort is then cooled in a heat exchanger when the temperature is fallen below 50°C further sludge begins to settle called a cold break.

Wort is filtered with kieselgur (diatomaceous earth).

Further, cooled wort is ready for fermentation, during transferring wort, the wort is oxygenated to provide the yeast with oxygen for initial growth. 

Fermentation

There are top and bottom fermentation 

In top fermentation -

Saccharomyces cerevisiae, temperature 15-16°C at the time of pitching - inoculation pf yeast is done in the wort. the temperature is raised around 20°C in 3 days entire fermentation time is around 6 days. Yeast flows on top i.e. scooped off and can be used for further pitching. 

In bottom fermentation - 

S. uvarum or S. eubayanus used in this process for 12 days, in this process yeast begin to settle down at the bottom. During fermentation carbon dioxide is released, this carbon dioxide begins to collapse after 4-5 days. 

Carbon dioxide and heat are removed by cooling and in this process, sugar is converted into alcohol. During fermentation wort, specific gravity decreases. The green beer we got at the end of fermentation. 

Green beer is harsh and bitter, in the lagering process it is stored in closed VAT for 0°C for 6-9 months. During this period secondary fermentation occurs that saturate beer with carbon dioxide and also material affecting the flavor like diacetyl, hydrogen sulfide, mercaptans, acetaldehyde is decreased by evaporation. 

Ester is increased - any tannins, protein still left are precipitated. Time can be reduced by carbonation. The beer is then stored at high temperature i.e. 40°C to remove the hydrogen sulfide or acetaldehyde, further chilled at 2°C to remove the chill haze then it is carbonated and kept for 20 days for two months.

Pasteurization - 

After aging, the beer can be pasteurized to kill the remaining yeast and prevent further alcohol production. This is accomplished by heating the beer above 135°F (57°C). This process, named after Louis Pasteur, is widely known for preserving milk. Interestingly, Pasteur originally developed this process to preserve beer in the 1860s. Pasteurization, however, is not used in the production of genuine draft beers. These beers are also known as "ice" beers since they must be kept refrigerated to preserve their flavor and slow the remaining yeast activity. Many consider the draft beers best in the aroma as well as taste.

Packaging - 

The beer is transferred to a pressure tank and distributed in cans or bottles. During the transfer, oxygen and carbon dioxide are not allowed to lose. Cans and bottles are washed in hot water sodium hydroxide for sterilizing and then it is filled and crowned or capped. Further passed through the pasteurized and kept for 60°C for 30 minutes.

Byproducts - 

Beer brewing produces several byproducts that can be used by other industries. 

1. During the malting of the barley, rootlets form on the grain and drip off. These can be collected and used for animal feed. 
2. The hops that are filtered out from the finished wort can also be collected and used again as fertilizer. 
3. The residual yeast from the brewing process is a rich source of B vitamins. It can be put to use by pharmaceutical companies to make vitamins or drugs, or used as a food additive. 
4. Used beer cans and beer bottles are routinely recycled.

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