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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Food Additives - E numbers

Food Additives and E numbers 

Food additives aren't a recent discovery, have been used by mankind for centuries. Our ancestors used salt to preserve meats and fish, added herbs and spices to improve the flavor of foods, preserved fruit with sugar, and pickled olives and cucumbers in a vinegar solution. 

Today, with the advent of processed foods, there has been a massive explosion in the chemical adulteration of foods with additives. Considerable controversy has been associated with the potential threats and possible benefits of food additives.

Why Use Additives? 

Food made at home is always at its best when eaten straight away. Food produced on a large scale that is needed to supply supermarkets and other food shops has to be transported and stored before it is consumed. It has to stay in the highest condition over a much longer period of time than home-cooked food. 

Food Additives are substances added intentionally to foodstuffs to perform certain technological functions, for example to colour, to sweeten, or to preserve, they are so essential that additives are used even in certain organic foods.

 In many countries, lots of food is lost because it 'goes off' due to microbial growth before it can be eaten. Food poisoning also shows the dangers of contaminated food and without the use of preservatives; it would quite likely be more common. 

However, a food additive is defined as any natural or artificial material, other than the basic raw ingredients, used in the production of a food item to improve the final product or any substance that may affect the characteristics of any food, including those used in the production, processing, treatment, packaging, transportation or storage of food. In the European Union (EU) Food additives are often referred to as E-numbers as in the European Union countries, additives are numbered with a prefix E. The E thus refers to an approved additive. Additives are not used to cover problems (such as spoiling) in the food, but are often used to prevent spoilage or other loss of quality. All additives are tested for toxicity and safety. However, side effects can never completely be excluded.

There are many categories of food additives, such as: 

1. Food Colours 
2. Preservatives 
3. Antioxidants 
4. Sweeteners 
5. Emulsifiers, Stabilisers, Thickeners, and Gelling Agents 
6. Flavour enhancers and flavourings  

Food Colours 

The primary reasons for adding colours to foods include: 

1.  To offset colour loss due to exposure to light, air, extremes of temperature, moisture, and storage conditions 
2.  To compensate for natural or seasonal variations in food raw materials or the effects of processing and storage to meet consumer expectations (Masking or disguising inferior quality, however, are unacceptable uses of colours). 
3.  To enhance colors that occur naturally but at levels weaker than those usually associated with a given food.

Colors commonly found include caramel (E150a), which is used in products such as gravy and soft drinks; and curcumin (E100), a yellow color extracted from turmeric roots. Some people think that adding color makes food look more attractive, while other people think added colors are unnecessary and misleading. 

 Preservatives 

These help stop food 'go off' and mean that food can be kept safe for longer. Most food that has a long shelf-life is likely to include preservatives unless another method of preservation has been used ' such as freezing, canning, or drying. For example, to stop mold or bacteria growing, dried fruit is often treated with sulphur dioxide (E220); and bacon, ham, corned beef, and other 'cured' meats are often treated with nitrite and nitrate (E249 to E252) during the curing process. More traditional preservatives such as sugar, salt, and vinegar are also still used to preserve some foods.

 Antioxidants 

Any food made using fats or oils - from meat pies to mayonnaise - is likely to contain antioxidants. These make foods last longer by helping to stop the fats, oils, and certain vitamins from combining with oxygen in the air - this is what makes food taste 'off' - become rancid and lose colour. Vitamin C, also called ascorbic acid or E300, is one of the most widely used antioxidants. 

Sweeteners 

The desire for the pleasure of sweetness has a strong influence on what people choose to eat and drink. Since early times, people have sought out foods with a sweet taste; for example, drawings on the walls of Egyptian tombs show bee-keepers collecting honey, and sugar cane was grown in India some 2000 years ago. Today, sucrose, or table sugar, is the taste standard by which all other sweeteners are measured. An "ideal" sweetener tastes like sucrose, is colourless, odourless, readily soluble, stable, and economical. Some sweeteners, like sugar, contain calories. And some are low-calorie or calorie-free.

Sweeteners are lower in calories and safer for teeth; sweeteners are often used instead of sugar in products such as fizzy drinks, yoghurt, and chewing gum. 'Intense sweeteners', such as aspartame (E951), saccharin (E954) and acesulfame-K (E950) are many times sweeter than sugar and so only very small amounts are used. Bulk sweeteners, such as sorbitol (E420), have about the same sweetness as sugar and so they are used in similar amounts to sugar. 

If you give concentrated soft drinks that contain sweeteners to children aged under 4, it's important to dilute them more than you would for an adult. This is to avoid children having large amounts of sweetener.

Emulsifiers, Stabilisers, Thickeners, and Gelling Agents

Add oil to water and the two liquids will never mix. At least not until an emulsifier is added. Emulsifiers are molecules with one water-loving (hydrophilic) and one oil-loving (hydrophobic) end. They make it possible for water and oil to become finely dispersed in each other, creating a stable, homogenous, smooth emulsion. Emulsifiers such as Lecithins (E322), help mix ingredients together that would normally separate, such as oil and water. Stabilizers, such as locust bean gum (E410) made from carob beans, help stop these ingredients from separating again. Emulsifiers and stabilizers also give foods a consistent texture. They are used in foods such as low-fat spreads and other sweet and savoury foods. The most common gelling agent is pectin (E440), which is used to make jam. 

Gelling agents are used to changing the consistency of food. Thickeners help give body to food in the same way as adding flour thickens a sauce Flavour enhancers and flavourings Flavour enhancers are used to bring out the flavour in a wide range of savoury and sweet foods without adding a flavour of their own. For example, monosodium glutamate (E621), known as MSG, is added to processed foods, especially soups, sauces, and sausages. Flavour enhancers are also used in a wide range of other foods including savoury snacks, ready meals, and condiments. Flavourings, in contrast, are added to a wide range of foods, usually in very small amounts, to give a particular taste or smell. Flavourings don't have E numbers because they are controlled by different laws to other food additives. Ingredients lists will say if flavourings have been used, but individual flavourings might not be named Salt, although not classed as a food additive, is the most widely used flavour enhancer.

Why are additives given E numbers? 

E numbers are codes for food additives and are usually found on food labels throughout the European Union. The numbering scheme follows that of the International Numbering System (INS) as determined by the Codex Alimentarius Committee. Only a subset of the INS additives are approved for use in the European Union, giving rise to the 'E' prefix. EU legislation requires most additives used in foods to be labelled clearly in the list of ingredients, either by name or by an E number. This provides you with information about the use of additives in foods and allows you to avoid foods containing specific additives if you wish. Giving an additive an E number means that it has passed safety tests and has been approved for use in the European Union. E numbers are universally adopted by the food industry worldwide, also encountered on food labelling in other jurisdictions, including Australia, and New Zealand. They are increasingly (though still rarely) found on North American packaging, especially in Canada. It is known that many E numbers contain unlisted ingredients in them generally additives derived from animals and insects not suitable for vegetarians, vegans or other groups each religious Muslim, Jew, and Hindu. 

Foods sold in the European Union (EU) have had full ingredient labelling since the mid-1980s. These include standard codes (E numbers) that accurately describe additives used in the production of food. These numbers are also used in Australia and New Zealand but without the E. Many of these additives were once of natural origin. However, most are now prepared/produced synthetically as these are often less expensive than the natural product.

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Ohmic Heating

 Ohmic Heating 

Also termed ‘resistance heating’ or ‘electro-heating’, this is a more recent development in which an alternating electric current is passed through food, and the electrical resistance of the food causes the power to be translated directly into heat. As the food is an electrical component of the heater, it is essential that its electrical properties (its resistance) are matched to the capacity of the heater.

The concept of direct heating in this way is not new, but it has been developed into a commercial process during the last 15 years by the APV Baker company, using a licensed design by EA Technology. The process can be used for UHT sterilization of foods, and especially those that contain large particles (up to 2.5 cm) that are difficult to sterilize by other means. It is now in commercial use in Europe, the USA, and Japan for: • aseptic processing of high added-value ready meals, stored at ambient temperature for

 • pasteurization of particulate foods for hot filling 

 • pre-heating products before canning 

 • high added-value prepared meals, distributed at chill temperatures (Fryer, 1995). 

Ohmic heating is more efficient than microwave heating because nearly all of the energy enters the food as heat. Another important difference is that microwave and radio frequency heating has a finite depth of penetration into a food whereas ohmic heating has no such limitation. However, microwave heating requires no contact with the food, whereas ohmic heating requires electrodes to be in good contact. In practice, the food should be liquid or have sufficient liquid with particulate foods to allow good contact and to pump the product through the heater. 

Principles

The principles of ohmic heating are very simple as illustrated in Figure. Ohmic heating is based on the passage of alternating electrical current (AC) through a body such as a liquid-particulate food system which serves as an electrical resistance in which heat is generated. AC voltage is applied to the electrodes at both ends of the product body. The rate of heating is directly proportional to the square of the electric field strength, E, and electrical conductivity. The electric field strength can be varied by adjusting the electrode gap or the applied voltage. However, the most important factor is the electrical conductivity of the product and its temperature dependence. If the product has more than one phase such as in the case of a mixture of liquid and particulates, the electrical conductivity of all the phases has to be considered. The electrical conductivity increases with rising temperature, suggesting that ohmic heating becomes more effective as temperature increases, which could theoretically result in runaway heating. A difference in the electrical resistance and its temperature dependence between the two phases can make the heating characteristics of the system very complicated. Since electrical conductivity is influenced by ionic content, it is possible to adjust the electrical conductivity of the product (both phases) with ion (e.g. salts) levels to achieve effective ohmic heating. 

In ohmic heating, microbes are thought to be thermally inactivated. Other contributions to the kill mechanism have also been suggested. A mild electroporation mechanism may occur during ohmic heating operating at low frequency (50–60 Hz) which allows electrical charges to build up and form pores across cell walls.

Advantages

The advantages of ohmic heating are as follows: 

• The food is heated rapidly (1ºC s-¹ ) at the same rate throughout and the absence of temperature gradients result in even heating of solids and liquids if their resistances are the same 
• Heat transfer coefficients do not limit the rate of heating 
• Temperatures sufficient for UHT processing can be achieved 
• There are no hot surfaces for heat transfer, as in conventional heating, and therefore no risk of surface    fouling or burning of the product which results in reduced frequency of cleaning 
• Heat-sensitive foods or food components are not damaged by localized overheating 
• Liquids containing particles can be processed and are not subject to shearing forces that are found in,      for example, scraped surface heat exchangers  
• It is suitable for viscous liquids because heating is uniform and does not have the problems associated     with poor convection in these materials 
• Energy conversion efficiencies are very high (>90%) 
• Lower capital cost than microwave heating 
• Suitable for continuous processing. 
• Heating food materials by internal heat generation without the limitation of conventional heat transfer    and some of the non-uniformity commonly associated with microwave heating due to limited dielectric penetration. Heating takes place volumetrically and the product does not experience a large temperature gradient within itself as it heats. 
• The higher temperature in particulates than liquid can be achieved, which is impossible for conventional heating. 
• Reducing risks of fouling on heat transfer surface and burning of the food product, resulting in minimal mechanical damage and better nutrients and vitamin retention. 
• High energy efficiency because 90% of the electrical energy is converted into heat. 
•  Optimization of capital investment and product safety as a result of high solids loading capacity. 
• Ease of process control with instant switch-on and shut-down. 
• Reducing maintenance cost (no moving parts). 
• Ambient-temperature storage and distribution when combined with an aseptic filling system. 
• A quiet environmentally friendly system.

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Hurdle Technology

Hurdle Technolgy in Food Preservation

In traditionally preserved foods, such as smoked fish or meat, jams, and other preserves, there is a combination of factors that ensure microbiological safety and stability of the food, and thus enable it to be preserved. In smoked products, for example, this combination includes heat, reduced moisture content, and anti-microbial chemicals deposited from the smoke onto the surface of the food. Some smoked foods may also be dipped or soaked in brine or rubbed with salt before smoking, to impregnate the flesh with salt and thus add a further preservative mechanism. Smoked products may also be chilled or packed in modified atmospheres to further extend the shelf life. In jams and other fruit preserves, the combined factors are heat, a high solids content (reduced water activity), and high acidity. These preservative factors also strongly influence the sensory characteristics of the product and contribute to important differences in flavor, texture, or color between different products.

In vegetable fermentation, the desired product quality, and microbial stability are achieved by a sequence of factors that arise at different stages in the fermentation process: the addition of salt selects the initial microbial population which uses up the available oxygen in the brine. This reduces the redox potential and inhibits the growth of aerobic spoilage micro-organisms and favors the selection of lactic acid bacteria. These then acidify the product and stabilize it. Further treatments may include pasteurization and packaging to extend the shelf life and facilitate distribution. The demand by consumers for high-quality foods having ‘fresh’ or ‘natural’ characteristics, that require a minimum amount of preparation has led to the development of ready-to-eat and convenience foods that are preserved using mild technologies. 

The main preservation technique is refrigeration, but because of the difficulty in maintaining sufficiently low temperatures throughout the production, distribution, and storage chain, additional barriers (or ‘hurdles’) are required to control the growth of spoilage or pathogenic micro-organisms. The concept of combining several factors to preserve foods has been developed by Leistner (1995) and others into the Hurdle effect (each factor is a hurdle that micro-organisms must overcome). This in turn has led to the application of Hurdle Technology, where an understanding of the complex interactions of temperature, water activity, pH, chemical preservatives, etc. are used to design a series of hurdles that ensure the microbiological safety of processed foods. 

The hurdles are also used to improve the quality of foods and the economic properties (for example, the weight of water that can be added to a food, consistent with its microbial stability). To be successful, the hurdles must take into account the initial numbers and types of micro-organisms that are likely to be present in the food. 

The hurdles that are selected should be ‘high enough’ so that the anticipated numbers of these microorganisms cannot overcome them. However, the same hurdles that satisfactorily preserve food when it is properly prepared (Fig.a), is overcome by a larger initial population of micro-organisms (Fig. b) when for example raw materials are not adequately cleaned. In this example, the main hurdles are low water activity and chemical preservatives in the product, with storage temperature, pH, and redox potential having a smaller effect. Blanching vegetables or fruits has a similar effect in reducing initial numbers of micro-organisms before freezing or drying. If in given fig., the same hurdles are used with a different product that is richer in nutrients that can support microbial growth (Fig.c), again the hurdles may be inadequate to preserve it and a different combination may be needed or the height of the hurdles increased. It should be noted that although the hurdles in Fig. are represented as a sequence, in practice the different factors may operate simultaneously, synergistically, or sequentially. The combination of hurdle technology and HACCP in process design is described by Leistner (1994). By combining hurdles, the intensity of individual preservation techniques can be kept comparatively low to minimize loss of product quality, while overall there is a high impact on controlling microbial growth. 

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How to read a scientific or research paper

Many times in our college assignments or in project reports or detailed studies work involves reading research papers. Because scientific articles are different from other texts, like novels, storybooks, or newspaper stories, they should be read and understood differently. Here are some tips to be able to read and understand them.

Scanning

First get the big picture by reading the title, keywords, and abstract carefully; this will tell you the major findings and why they matter.

Quickly scan the article without taking notes; focus on headings and subheadings.

Note the publishing date; for many areas, current research is more relevant.

Note any terms and parts you don't understand for further reading.

Go-over

Read the article again, asking yourself questions such as:

    What problem is the study trying to solve?

    Are the findings well supported by evidence?

    Are the findings unique and supported by other work in the field?

    What was the sample size? Is It representative of the larger population?

    Is the study repeatable?

    What factor s might affect the results?

     If you are unfamiliar with the key concept, look for them in the literature.

Interpret

Examine the graphs and tables carefully.

Try to interpret data first before looking at captions.

When reading the discussion and results, look for key issues, and new findings.

Make sure you have distinguished the main points. If not, go over the text again.

Summarize

Take notes; it Improves reading comprehension and helps you remember key points.

If you have a printed version, highlight key points, and write on the article. If it's on-screen, make use of markers and comments.

For the basic understanding of research papers consist of the following headings -

Tittle 

A summary of the study and findings, written by the author.

Introduction

A statement of what is currently known about the study subject that articulates the question being investigated. It cites other scholarly works, lays the foundations for the study, and sometimes states a hypothesis to be tested.

Results 

A description of the research conducted and the results obtained. 

Results are presented as tables, large datasets, and figures, which can include graphs, videos, diagrams, and photographs.

Some papers include additional supporting data as a supplement.

Discussion

Analysis and interpretation of the data presented that integrates the new information with prior findings, state the implications of the work, and sometimes generates new hypotheses to be tested.

Methods

A description of how the studies were conducted, with sufficient detail so that others can repeat them exactly.

References

The list of the articles cited in the paper that provide information on the research topic and the methods used.

Try to read a research paper from the topics which you are interested in and self-check yourself whether you are getting it or not. You can get the research papers from scholar.google.com or for food technology-related research papers you can visit http://foodtechnologyinfo.com/ under the student corner. 

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Effect of blanching on foods

 

As we know that blanching is the most common and easiest way to preserve the fruits and vegetables for short shelf life and also it is done prior to any processing. Throughout college, it is one of my favorite topics. But do we know that what are the after-effects of blanching on foods? Let me explain about it further - 

In general, the time-temperature combination used for blanching is a compromise which ensures adequate enzyme inactivation but prevents excessive softening and loss of flavor in the food.

Nutrients

Some minerals, water-soluble vitamins, and other water-soluble components are lost during blanching. Losses of vitamins are mostly due to leaching, thermal destruction, and, to a lesser extent, oxidation. The extent of vitamin loss depends on a number of factors including: 

• the maturity of the food and variety 

• methods used in the preparation of the food, particularly the extent of cutting, slicing or dicing

the surface-area-to-volume ratio of the pieces of food 

• method of blanching 

• time and temperature of blanching (lower vitamin losses at higher temperatures for shorter times)

• the method of cooling • the ratio of water to food (in both water blanching and cooling).  

Colour and flavor

Blanching brightens the color of some foods by removing air and dust on the surface and thus altering the wavelength of reflected light. The time and temperature of blanching also influence the change in food pigments according to their D value. Sodium carbonate (0.125% w/w) or calcium oxide are often added to blancher water to protect chlorophyll and to retain the color of green vegetables, although the increase in pH may increase the losses of ascorbic acid. Enzymic browning of cut apples and potatoes is prevented by holding the food in dilute (2% w/w) brine prior to blanching. When correctly blanched, most foods have no significant changes to flavor or aroma, but under-blanching can lead to the development of off-flavors during the storage of dried or frozen foods. Changes in color and flavor are described in more detail by Selman (1987).

Texture

One of the purposes of blanching is to soften the texture of vegetables to facilitate filling into containers prior to canning. However, when used for freezing or drying, the time– temperature conditions needed to achieve enzyme inactivation cause an excessive loss of texture in some types of food (for example certain varieties of potato) and in large pieces of food. Calcium chloride (1–2%) is therefore added to blancher water to form insoluble calcium pectate complexes and thus to maintain firmness in the tissues.

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Basic to advance in Blanching

 

Blanching

Blanching serves a variety of functions, one of the main ones being to destroy enzymic

activity in vegetables and some fruits, prior to further processing. As such, it is not

intended as a sole method of preservation but as a pre-treatment which is normally carried

out between the preparation of the raw material and later operations

(particularly heat sterilization, dehydration, and freezing).

Blanching is also combined with peeling and/or cleaning of food, to achieve

savings in energy consumption, space, and equipment costs.

A few processed vegetables, for example, onions and green peppers, do not require

blanching to prevent enzyme activity during storage, but the majority suffer considerably

loss in quality if the blanching is omitted or if they are under-blanched. To achieve adequate

enzyme inactivation, food is heated rapidly to a pre-set temperature, held for a pre-set

time and then cooled rapidly to near ambient temperatures. The factors which influence

blanching time is:

• type of fruit or vegetable

• size of the pieces of food

• blanching temperature

• method of heating

Theory

The theory of unsteady-state heat transfer by conduction and convection, which is used to

calculate blanching time.

The maximum processing temperature in freezing and dehydration is insufficient to

inactivate enzymes. If the food is not blanched, undesirable changes in sensory

characteristics and nutritional properties take place during storage. In canning, the time

taken to reach sterilizing temperatures, particularly in large cans, may be sufficient to

allow enzyme activity to take place. It is, therefore, necessary to blanch foods prior to

these preservation operations. Under-blanching may cause more damage to food than the

absence of blanching does, because heat, which is sufficient to disrupt tissues and release

enzymes, but not inactivate them, causes accelerated damage by mixing the enzymes and

substrates. In addition, only some enzymes may be destroyed which causes increased

activity of others and accelerated deterioration.

The heat resistance of enzymes is characterized by D and z values.

Enzymes which cause a loss of eating and nutritional qualities in vegetables and fruits

include lipoxygenase, polyphenol oxidase, polygalacturonase, and chlorophyllase. Two

heat-resistant enzymes that are found in most vegetables are catalase and peroxidase.

Although they do not cause deterioration during storage, they are used as marker enzymes

to determine the success of blanching. Peroxidase is the more heat resistant of the two, so

the absence of residual peroxidase activity would indicate that other less heat-resistant

enzymes are also destroyed. The factors that control the rate of heating at the center of the

product  and can be summarised as:

• the temperature of the heating medium

• the convective heat transfer coefficient

• the size and shape of the pieces of food

• the thermal conductivity of the food.

Blanching reduces the number of contaminating micro-organisms on the surface of

foods and hence assists in subsequent preservation operations. This is particularly

important in heat sterilization, as the time and temperature of processing are

designed to achieve a specified reduction in cell numbers. If blanching is inadequate, a

larger number of micro-organisms are present initially and this may result in a larger

number of spoiled containers after processing. Freezing and drying do not substantially

reduce the number of micro-organisms in unblanched foods and these are able to grow on

thawing or rehydration.

Blanching also softens vegetable tissues to facilitate filling into containers and

removes air from intercellular spaces which increases the density of food and assists in

the formation of a head-space vacuum in cans.  

Equipment  

The two most widespread commercial methods of blanching involve passing food

through an atmosphere of saturated steam or a bath of hot water. Both types of equipment

are relatively simple and inexpensive. Microwave blanching is not yet used commercially

on a large scale.  

Steam blanchers

In general, this is the preferred method for foods with a large area of cut surfaces

as leaching losses are much smaller than those found using hot-water blanchers.

At its simplest a steam blancher consists of a mesh conveyor belt that carries

food through a steam atmosphere in a tunnel. The residence time of the food is

controlled by the speed of the conveyor and the length of the tunnel. Typically a 

tunnel is 15 m long and 1–1.5 m wide. The efficiency of energy consumption is 

19% when water sprays are used at the inlet and outlet to condense escaping steam. 

Alternatively, food may enter and leave the blancher through rotary valves or hydrostatic

seals to reduce steam losses and increase energy efficiency to 27%, or steam

may be re-used by passing through Venturi valves. Energy efficiency

is improved to 31% using combined hydrostatic and Venturi devices (Scott et al., 1981).

In conventional steam blanching, there is often poor uniformity of heating in the

multiple layers of food. The time-temperature combination required to ensure enzyme

inactivation at the center of the bed results in overheating of food at the edges and a

consequent loss of texture and other sensory characteristics. Individual quick blanching

(IQB) which involves blanching in two stages, was developed to overcome this problem

(Lazar et al., 1971). In the first stage, the food is heated in a single layer to a sufficiently

high temperature to inactivate enzymes. In the second stage (termed adiabatic holding) a

deep bed of food is held for sufficient time to allow the temperature at the center of each

piece to increase to that needed for enzyme inactivation. The reduced heating time (for

example 25 s for heating and 50 s for holding 1 cm diced carrot compared with 3 min for

conventional blanching), results in an improvement in the efficiency of energy

consumption to 86–91% (Cumming et al., 1984). The mass of product blanched per

kilogram of steam increases from 0.5 kg per kilogram of steam in conventional steam

blanchers to 6–7 kg per kilogram of steam, when small-particulate foods (for example

peas, sliced or diced carrots) are blanched.

Nutrient losses during steam blanching are reduced by exposing the food to warm air

(65ºC) in a short preliminary drying operation (termed ‘pre-conditioning’). Surface

moisture evaporates and the surfaces then absorb condensing steam during IQB. Weight

losses are reduced to 5% of those found using conventional steam blanching (Lazar et al.,

1971). Pre-conditioning and individual quick blanching are reported to reduce nutrient

losses by 81% for green beans, by 75% for Brussels sprouts, by 61% for peas, and by 53%

for lima beans and there is no reduction in the yield of blanched food (Bomben et al.,

1973).

The equipment for IQB steam blanching consists of a bucket elevator

that carries the food to a heating section. The elevator is located in a close-fitting tunnel

to reduce steam losses. A single layer of food is heated on a conveyor belt and then held

on a holding elevator before cooling. The cooling section employs a fog spray to saturate

the cold air with moisture. This reduces evaporative losses from the food and reduces the

amount of effluent produced. Typically the equipment processes up to 4500 kg h power -1 of

food. The complete inactivation of peroxidase is achieved with a minimum loss in

quality, indicated by the retention of 76–85% of ascorbic acid.

Batch fluidized-bed blanchers operate using a mixture of air and steam, moving at

approximately 4.5 m s power -1, which fluidizes and heats the product simultaneously. The

design of the blanching chamber promotes continuous and uniform circulation of the food

until it is adequately blanched. Although these blanchers have not yet been widely used at

a commercial scale, they are reported to overcome many of the problems associated with

both steam and hot-water methods (Gilbert et al., 1980). The advantages include:

• faster, more uniform heating

• good mixing of the product

• a substantial reduction in the volume of effluent

• shorter processing times and hence smaller losses of vitamins and other soluble heat

sensitive components of food.

A continuous fluidized-bed blancher is described by Philippon (1984).

 Hot-water blanchers

There are a number of different designs of blancher, each of which holds the food in hot

water at 70–100ºC for a specified time and then removes it to a dewatering-cooling

section. 

In the widely used reel blancher, food enters a slowly rotating cylindrical mesh drum

which is partly submerged in hot water. The food is moved through the drum by internal

flights. The speed of rotation and length control the heating time. Pipe blanchers consist

of a continuous insulated metal pipe fitted with feed and discharge ports. Hot water is

recirculated through the pipe and food is metered in. The residence time of food in the

blancher is determined by the length of the pipe and the velocity of the water. These

blanchers have the advantage of a large capacity while occupying small floor space. In

some applications, they may be used to transport food simultaneously through a factory.

Developments in hot-water blanchers, based on the IQB principle, reduce energy

consumption, and minimize the production of effluent. For example, the blancher-cooler

has three sections: a pre-heating stage, a blanching stage, and a cooling stage. The

food remains on a single conveyor belt throughout each stage and therefore does not

suffer the physical damage associated with the turbulence of conventional hot water

blanchers. The food is pre-heated with water that is recirculated through a heat

exchanger. After blanching, a second recirculation system cools the food. The two

systems pass water through the same heat exchanger, and this heats the pre-heat water

and simultaneously cools the cooling water. Up to 70% of the heat is recovered. A

recirculated water-steam mixture is used to blanch the food, and final cooling is by cold

air. Effluent production is negligible and water consumption is reduced to approximately

1 m3 per 10 t of product. The mass of product blanched is 16.7–20 kg per kilogram of

steam, compared with 0.25–0.5 kg per kilogram in conventional hot-water blanchers. 

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Constituents of food and its functions

Carbohydrates:

Carbohydrates, in simplest terms, are sugars and contain carbon, hydrogen, and oxygen. They are the main source of energy in the human diet. Carbohydrates can be classified as monosaccharides, the simplest form which includes include glucose, galactose, and fructose; disaccharides such as lactose, maltose, and sucrose which consists of two units of simple sugars, and the most complex polysaccharides that consist of more than two units of monosaccharides viz. starch and cellulose. Rice, maize, wheat, barley, potato, sugarcane, beetroot, banana, grapes, etc. are some of the important sources of carbohydrates. Carbohydrates are broken down by the process known as oxidation and energy thus released is utilized by the body to carry out all the functions. The released energy is measured in calories. 

Carbohydrates lecture series + 50 Questions + Gate Questions

Proteins:

Amino acids are the building blocks of proteins. Proteins are complex high molecular weight compounds that play a structural and functional role in all living cells. They are essential for the growth and repair of the body tissues. In terms of human nutrition, proteins are of two types depending on their source – animal protein such as milk, cheese, meat, egg, etc. and vegetable protein such as pulses, soya beans, nuts, and grains. Proteins are metabolized to provide energy when the body is starved and is devoid of any carbohydrate source.

Fats:

This is the most concentrated source of energy. Fats are made up of carbon, hydrogen, and oxygen; the oxygen content is much lesser as compared to that of carbohydrates resulting in the production of a larger amount of energy when oxidized. Fat forms energy reserves in the body and is mainly stored under the skin. Butter, ghee, milk, fish, meat, nuts, and oils are the main sources of fat. One gram of fat when burnt gives nine calories of energy.

Vitamins:

Vitamins are vital for maintaining normal growth and health. Unlike carbohydrates, proteins, and fats, vitamins do not provide energy but they are essential for the proper absorption of carbohydrates, proteins, fats and minerals by the body. The various types of vitamins are A, B, C, D, E, and K. There is no single food that provides all the vitamins required for our body, hence a variety of foods should be taken in balance in order to obtain all these vitamins in required amounts. The deficiency of vitamins leads to various disorders.

Minerals:

Minerals such as iron, calcium, copper, iodine, sodium, phosphorus, zinc, etc. along with vitamins are required in small quantities by our body for normal growth and proper functioning. Iron is the main component of hemoglobin that transports oxygen to tissues. Calcium is required for the formation of bones and teeth. Likewise, each of the minerals has a role in maintaining body functions.

Water:

Water constitutes 70% of our body and is required for all the biological processes in our body. It is essential for transporting food, hormones, and other nutrients throughout the body. It flushes out toxins and other wastes out of the body in the form of urine and sweat. It regulates body temperature

Roughage:

The fiber content of our diet that helps in easy movement of food in the alimentary canal is known as roughage. It is essential for the proper functioning of the digestive system. Fruits, vegetables, corn, salads, and cereals are highly fibrous foods.

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The food industry today

The food industry today 

The aims of the food industry today, as in the past, are fourfold: 

1. To extend the period during which food remains wholesome (the shelf life) by preservation techniques that inhibit microbiological or biochemical changes and thus allow time for distribution, sales, and home storage.

 2. To increase variety in the diet by providing a range of attractive flavors, colors, aromas, and textures in food (collectively known as eating quality, sensory characteristics, or organoleptic quality); a related aim is to change the form of the food to allow further processing (for example the milling of grains to flour). 

3. To provide the nutrients required for health (termed nutritional quality of food). 

4. To generate income for the manufacturing company. Each of these aims exists to a greater or lesser extent in all food production, but the processing of a given product may emphasize some more than others. 

For example, frozen vegetables are intended to have sensory and nutritional qualities that are as close as possible to the fresh product, but with a shelf life of several months instead of a few days or weeks. The main purpose of freezing is therefore to preserve the food. In contrast, sugar confectionery and snackfoods are intended to provide variety in the diet and a large number of shapes, flavors, colors, and textures are produced from basic raw materials. All food processing involves a combination of procedures to achieve the intended changes to the raw materials. These are conveniently categorized as unit operations, each of which has a specific, identifiable, and predictable effect on food. Unit operations are grouped together to form a process. The combination and sequence of operations determine the nature of the final product. 

In industrialized countries the market for processed foods is changing, and in contrast to earlier years, consumers no longer require a shelf life of several months at ambient temperature for the majority of their foods. Changes in family lifestyle, and increased ownership of freezers and microwave ovens, are reflected in demands for foods that are convenient to prepare, are suitable for frozen or chilled storage, or have a moderate shelf Introduction life at ambient temperatures. There is now an increasing demand by consumers for foods that have fewer synthetic additives, or have undergone fewer changes during processing. These foods more closely resemble the original raw materials and have a ‘healthy’ or ‘natural’ image. Correspondingly, growth in demand for organic foods has significantly increased in Europe during the 1990s.

 These pressures are an important influence on changes that are taking place in the food processing industry, and manufacturers have responded by reducing or eliminating synthetic additives from products (particularly colorants and flavors) and substituting them with natural or ‘nature-equivalent’ alternatives. They have also introduced new ranges of low-fat, sugar-free or low-salt products in nearly all sub-sectors (Anon., 1999). New products that are supplemented with vitamins, minerals, and probiotic cultures (or ‘functional’ foods) have appeared in recent years, and products containing organic ingredients are now widely available. At the time of writing (2000), a debate over the safety of genetically modified (GM) food ingredients is unresolved. Consumer pressure for more ‘natural’ products has also stimulated the development of novel ‘minimal’ processes that reduce the changes to sensory characteristics or nutritional value of foods. Improvements to food quality during the last 10–15 years have also been achieved through changes in legislation, including legal requirements on manufacturers and retailers to display ‘due diligence’ in protecting consumers from potentially hazardous foods.

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