FOOD BIOTECHNOLOGY BIT 313 3(3-0). Dr. Zaffar Mehmood. Definitions:. Food: means a raw, cooked, or processed edible substance, ice, beverage, or ingredient used or intended for use or for sale in whole or in part for human consumption, or chewing gum.
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c. Oxidation of the terminal −CH2OH to −COOH converts the sugar into a -uronic acid, such as glucuronic acid.
the use of mild conditions of pH and temperature which maintain (and often improve)
the nutritional properties and sensory characteristics of the food
• the production of foods which have flavours or textures that cannot be achieved by other methods
• low energy consumption due to the mild operating conditions
• relatively low capital and operating costs
• relatively simple technologies.
The main advantages of technical enzymes are:
• they cause highly specific and controlled changes to foods
• there is minimal loss of nutritional quality at the moderate temperatures employed
• lower energy consumption than corresponding chemical reactions
• the production of new foods, not achievable by other methods.
The main factors that control the growth and activity of micro-organisms in food
• availability of carbon and nitrogen sources, and any specific nutrients required by
• substrate pH
• moisture content
• incubation temperature
• redox potential
• stage of growth of micro-organisms
• presence of other competing micro-organisms
micro-encapsulation in polymer membranes which retain the enzyme but permit the passage of substrates and products
• electrostatic attachment to ion exchange resins
• adsorption onto colloidal silica and/or cross linking with glutaraldehyde
• covalent bonding to organic polymers
• entrapment in polymer fibres (for example cellulose triactetate or starches)
• co-polymerisation with maleic anhydride
• adsorption onto charcoal, polyacrylamide, or glass
the higher cost of carriers, equipment and process control
• changes to the pH profiles and reaction kinetics of enzymes
• loss of activity (25–60% loss)
• risk of microbial contamination
The requirements of commercial enzyme production from micro-organisms are as follows:
• micro-organisms must grow well on an inexpensive substrate
• substrates should be readily available in adequate quantities, with a uniform quality
• micro-organisms should produce a constant high yield of enzyme in a short time
• methods for enzyme recovery should be simple and inexpensive
• the enzyme preparation should be stable
dough allowed to rise, turned and folded rounding intermediate proof moulding Panning pan proof baking cooling slicing .
Dividing and scaling rounding intermediate proof Moulding panning pan proof baking cooling slicing.
Requirement: Continuous beer fermentation
Major issue of contamination.
Choice of Carrier material:
be spontaneous or induced by linking agents;
(ii) Entrapment within a porous matrix;
(iii) containment behind or within a barrier;and
(iv) self-aggregation, naturally or artificially induced
The production of lactic acid by lactic acid bacteria decreases the pH of the milk to cause coagulation of the casein. A pH below 5.3, colloidal calcium phosphate is solubilized from the casein micelle, causing the micelles to dissociate and the casein proteins to aggregate and precipitate at the isoelectric point of casein (pH 4.6). The resulting gel, which is somewhat fragile in nature, provides the structure for sour cream, yogurt, and acid-precipitated cheeses, such as cream cheese andcottage cheese.
Many commercial dairy processors now use the direct vat inoculation (DVI) process for frozen or freeze-dried cultures (up to 1012 bacteria per gram of starter) in the processing of cultured dairy products.
Rennet:a mixture of chymosinand pepsin, obtained from calf stomach, is most commonly recognized as the enzyme for coagulation of casein.
Proteases: from microorganisms and produced through recombinant DNA technologies have been successfully adapted as alternatives to calf rennet.
Chymosin: in rennet, cleaves the peptide bond between Phe-105 and Met-106 of κ-casein, releasing the hydrophilic, charged casein macropeptide, while the para-κ-casein remains associated with the casein micelle. The loss of the charged macropeptide reduces the surface charge of the casein micelle and results in the aggregation of the casein micelles to form a gel network stabilized by hydrophobic interactions.
Temperature influences both the rate of the enzymatic reaction and the aggregation of the casein proteins, with 40–42◦C, the optimal temperature for casein coagulation. The use of rennet to hydrolyze the peptide bond and cause aggregation of the casein micelles is used in the manufacture of most ripened cheeses .
Milk fat globules have a tendency to coalesce and separate upon
standing. Homogenization reduces the diameter of the fat globules
from 1–10 μm to less than 2 μm and increases the total
fat globule surface area.
The physical change in the fat globule occurs through forcing the milk through a small orifice under high pressure. The decrease in the size of the milk fat globules reduces the tendency of the fat globules to aggregate during the gelation period.
In addition, denaturation of the whey proteins and interactions of the whey proteins with casein or the fat globules can alter the physical and chemical properties of the milk proteins to result in a firmer gel with reduced syneresis. Milk to be used to process yogurt, cultured buttermilk, and unripened cheeses is commonly homogenized to improve the quality of the final product.
The heat process, which must be sufficient to inactivate alkaline phosphatase, also destroys many pathogenic and spoilage microorganisms, and enzymes that may have a negative impact on the quality of the finished products.
The time-temperature treatments for the fluid milk pasteurization
have been adapted for the milk to be used in the processing of
cultured dairy products (62.8◦C for 30 minutes or 71.1◦C for
More severe heat treatments than characteristic of pasteurization causes denaturation of whey proteins and interactions between β-lactoglobulin and κ-casein. In cheeses, this interaction decreases the ability of chymosin to hydrolyzethe casein molecule and initiate curd precipitation and formation.
Pasteurization has a significant effect of the flavor profile of the milk. Cultured dairy products produced from pasteurized milks tend to have less intense flavor characteristics due to the heat inactivation of the naturally occurring microorganisms and enzymes in the milk that contribute to flavorformation.
Lactones and heterocycles are also formed during the heat treatment of raw milk to contribute cooked flavors.
The processing of cultured dairy products relies on the metabolic activity of the starter cultures to contribute to acid formation and flavorand texture development.
Once the desired pH or titratable acidity is reached for these products, the products are cooled to 5–10◦C to slow the growth of the bacteria and limit further acid production and other biological reactions.
Probiotics are live microorganisms which, when administered in sufficient quantity, confer a health benefit to the host. They must have (a). Viable cells (b). Enough quantity.
Official recognition. In light of these potential health benefits,digestivehealth is considered as one of the ten key food trends for 2010. Market predicted to reach US$30 billion by 2015 (Starling 2010).
Prebiotics are nondigestible food ingredients that beneficially
affect the host by selectively stimulating the growth and/or activity
of one or a limited number of bacteria in the GI system, and thereby confer health benefits to the host (Roberfroid 2007).
This definition overlaps with the definition of dietary fiber, with
the exception of its selectivity for certain bacterial species and
a wider range of health effects. Peptides, proteins, and lipids
contain prebiotics characteristics, but some carbohydrates have
received the most attention, including lactulose, inulin, and a
range of oligosaccharides that supply a source of fermentable
carbohydrate for the beneficial bacteria in the colon (Prado et al.