Dough

The rheological properties of dough are important in determining the baking quality of flour. For many years the Farinograph was used to measure the physical properties of dough. The Farinograph is a dough mixer hooked up to a dynamometer for recording Figure 8-28 Mechanical Model for Postmortem Striated Muscle. Source From C.W. Brabender Instruments, Inc., South Hackensack, New Jersey. torque. The instrument can measure water absorption of flour. A typical Farinograph curve is presented in...

Intentional Additives

Chemicals that are intentionally introduced into foods to aid in processing, to act as preservatives, or to improve the quality of the food are called intentional additives. Their use is strictly regulated by national and international laws. The National Academy of Sciences (1973) has listed the purposes of food additives as follows to improve or maintain nutritional value to enhance consumer acceptability to make the food more readily available to facilitate preparation of the food The use of...

Preservatives

Preservatives or antimicrobial agents play an important role in today's supply of safe and stable foods. Increasing demand for convenience foods and reasonably long shelf life of processed foods make the use of chemical food preservatives imperative. Some of the commonly used preservatives such as sulfites, nitrate, and salt have been used for centuries in processed meats and wine. The choice of an antimicrobial agent has to be based on a knowledge of the antimicrobial spectrum of the...

Unsaponifiables

Antioxidant Oil Low Thermal Volatility

The unsaponifiable fraction of fats consists of sterols, terpenic alcohols, aliphatic alcohols, squalene, and hydrocarbons. The distribution of the various components of the unsaponifiable fraction in some fats and oils is given in Table 2-19. In most fats the major components of the unsaponifiable fraction are sterols. Animal fats contain cholesterol and, in some cases, minor amounts of other sterols such as lanosterol. Plant fats and oils contain phytosterols, usually at least three, and...

Poly mer

Figure 10-22 Methods of Immobilizing Enzymes. Source From H.H. Weetall, Immobilized Enzymes and Their Application in the Food and Beverage Industry, Process Biochem., Vol. 10, pp. 3-6, 1975. Exhibit 10-1 Summary of Enzyme Immobilization Methods reactors, the reaction product is separated from the reaction mixture by a semipermeable membrane. In two-phase systems, a hydrophobic reaction product can be separated from the aqueous reaction mixture by transfer to the organic solvent phase. In...

L

C stimulus concentration R response magnitude Rs maximum response K equilibrium constant for the stimulus-receptor reaction K values reported by Beidler for many substances are in the range of 5 to 15. It appears that the initial step in the stimulus-receptor reaction is the formation of a weak complex, as evidenced by the small values of K. The complex formation results in the initiation of the nerve impulse. Taste responses are relatively insensitive to changes in pH and temperature. Because...

Water binding of meat

According to Hamm (1962), the waterbinding capacity of meat is caused by the muscle proteins. Some 34 percent of these proteins are water-soluble. The main portion of meat proteins is structural material. Only about 3 percent of the total water-binding capacity of muscle can be attributed to water-soluble (plasma) proteins. The main water-binding capacity of muscle can be attributed to actomyosin, the main component of the myofibrils. The adsorption isotherm of freeze-dried meat has the shape...

Yv

Figure 6-21 Relationship Between Crocin and Picrocrocin and the Carotenoids. Source From E.C. Grob, The Biogenesis of Carotenes and Carotenoids, in Carotenes and Carotenoids, K. Lang, ed., 1963, Steinkopff Verlag. Figure 6-22 Structure of Some of the Important Carotenoids. Source From B. Borenstein and R.H. Bunnell, Carotenoids Properties, Occurrence, and Utilization in Foods, in Advances in Food Research, Vol. 15, C.O. Chichester et al., eds., 1967, Academic Press. Figure 6-22 Structure of...

Isotherm In Food Chemistry

Food Chemistry Water Food Systems

Figure 8-36 Viscosity and Granule Appearance in the Viscoamylograph of 5 Suspension in Water of Cross-Bonded Waxy Corn. A 1 cross-bond per 10,000 glucose units, B 3 cross-bonds, C 6 cross-bonds, and D granule appearance. Source Reprinted from L.H. Kruger and R. Murray, Starch Texture, in Rheol-ogy and Texture in Food Quality, J.M. deMan, P.W. Voisey, V.F. Raspar, and D.W. Stanley, eds., 1976, Aspen Publishers, Inc. Figure 8-37 Viscosity and Granule Appearance in the Viscoamylograph of...

Nature and function

Enzymes are proteins with catalytic properties. The catalytic properties are quite specific, which makes enzymes useful in analytical studies. Some enzymes consist only of protein, but most enzymes contain additional nonprotein components such as carbohydrates, lipids, metals, phosphates, or some other organic moiety. The complete enzyme is called holoenzyme the protein part, apoenzyme and the nonprotein part, cofactor. The compound that is being converted in an enzymic reaction is called...

Cie system

The spectral energy distribution of CIE light sources A and C is shown in Figure 6-2. CIE illuminant A is an incandescent light operated at 2854 K, and illuminant C is the same light modified by filters to result in a Figure 6-1 Spectrophotometric Curves of Colored Objects. Source From Hunter Associates Lab., Inc. Figure 6-1 Spectrophotometric Curves of Colored Objects. Source From Hunter Associates Lab., Inc. spectral composition that approximates that of normal daylight. Figure 6-2 also shows...

Antioxidants

Food antioxidants in the broadest sense are all of the substances that have some effect on preventing or retarding oxidative deterioration in foods. They can be classified into a number of groups (Kochhar and Rossell 1990). Primary antioxidants terminate free radical chains and function as electron donors. They include the phenolic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxy-toluene (BHT), tertiary butyl hydroquinone (TBHQ), alkylgalates, usually propylgallate (PG), and...

HS1OOOOOOi

Figure 10-2 Mode of Action of Proline-Specific Peptidases. Source Reprinted with permission from M.B. Habibi-Najafi and B.H. Lee, Bitterness in Cheese A Review, Crit. Rev. Food Sci. Nutr., Vol. 36, No. 5, p. 408. Copyright CRC Press, Boca Raton, Florida. described in three ways by a systematic name, by a trivial name, and by a number of the Enzyme Commission (EC). Thus, the enzyme a-amylase (trivial name) has the systematic name a-l,4-glucan-4-glucanohy-drolase, and the number EC 3.2.1.1. The...

Additives and Contaminants

The possibility of harmful or toxic substances becoming part of the food supply concerns the public, the food industry, and regulatory agencies. Toxic chemicals may be introduced into foods unintentionally through direct contamination, through environmental pollution, and as a result of processing. Many naturally occurring food compounds may be toxic. A summary of the various toxic chemicals in foods (Exhibit 11-1) was presented in a scientific status summary of the Institute of Food...

L cr

At equilibrium the product of the concentrations of diffusable ions on the left side of the membrane must be equal to the product on the right side, shown as follows In addition, the sum of the cations on one side must equal the sum of anions on the other side and vice versa Na+ L Pr L + C1- L and Na+ R C1- R This is called the Gibbs-Donnan equilibrium and provides an insight into the reasons for the higher concentration of sodium ions in the intracellular fluid. Occasionally, phosphates can...

Srt1 QH2COOR

R'COO - H- sn-2 sn-3- CH2COOR Figure 2-8 Stereospecific Numbering of the Carbons in a Triacylglycerol The theory of restricted random distribution was proposed by Kartha (1953). In this theory the fatty acids are distributed at random, but the content of fully saturated glycer-ides is limited to the amount that can remain fluid in vivo. This theory is followed by the 1,3 random, 2 random distribution hypothesis of Vander Wal (1964). According to this theory, all acyl groups at the 2-positions...

Crystal Growth and Nucleation

The Effect Moisture Crystal Growth

Crystal growth, in contrast to nucleation, occurs readily at temperatures close to the freezing point. It is more difficult to initiate crystallization than to continue it. The rate of ice crystal growth decreases with decreasing temperature. A schematic graphical representation of nucleation and crystal growth rates is given in Figure 1-20. Solutes of many types and in quite small amounts will greatly slow ice crystal growth. The mechanism of this action is not known. Membranes may be...

Rheological Properties In Foods In Food Chemistry

Rheological Instrumental Techniques

Food texture can be defined as the way in which the various constituents and structural elements are arranged and combined into a micro- and macrostructure and the external manifestations of this structure in terms of flow and deformation. Most of our foods are complex physico-chemical structures and, as a result, the physical properties cover a wide range from fluid, Newtonian materials to the most complex disperse systems with semisolid character. There is a direct relationship between the...

Non Enzymatic Browning

Food Sulfur Chemistry

Figure 3-4 Reactions Involved in Sulfhydryl Polymerization of Proteins. Source From O. Kirchmeier, The Physical-Chemical Causes of the Heat Stability of Milk Proteins, Milchwissenschaft German , Vol. 17, pp. 408-412,1962. foods Figure 3-6 . Other factors that influence the browning reaction are temperature, pH, moisture level, oxygen, metals, phosphates, sulfur dioxide, and other inhibitors. The browning reaction involves a number of steps. An outline of the total pathway of melanoidin...

Component Fatty Acids

Even-numbered, straight-chain saturated and unsaturated fatty acids make up the greatest proportion of the fatty acids of natural fats. However, it is now known that many other fatty acids may be present in small amounts. Some of these include odd carbon number acids, branched-chain acids, and hydroxy acids. These may occur in natural fats products that occur in nature , as well as in processed fats. The latter category may, in addition, contain a variety of isomeric fatty acids not normally...