Specific Problem Foods

The numerous purely chemical papers are considered to be outside the scope of this paper. The reader is referred to several reviews on the subject (25-301. Comprehensive reviews on nonenzymic browning in relation to specific food problems had been published (31,32,33). 

Plastics packaging and contained food products are chemically related in four distinct ways. This relationship is based largely on the permeation property of the plastic material. Direct chemical reaction between plastic and product is seldom a problem when inert plastics such as polyethylene are used. However, polyethylene can transmit minute amounts of product to the outside. This paper examines the effect of permeation through the plastic wall and the direct effects of the plastic on the food product. Specific food packaging applications and methods of testing are discussed. 

There are problems as well in the absorption of certain drugs in the presence of specific food components. L-Dopa absorption may be inhibited in the presence of certain amino acids formed from the digestion of proteins [43], The absorption of tetracycline is reduced by calcium salts present in dairy foods and by several other cations, including magnesium and aluminum [115-117], which are often present in antacid preparations. In addition, iron and zinc have been shown to reduce tetracycline absorption [118], Figure 17 illustrates several of these interactions. These cations react with tetracycline to form a water-in-soluble and nonabsorbable complex. Obviously, these offending materials should not be co-administered with tetracycline antibiotics. 

Application of data obtained from simple clean reaction systems in biological or chemical studies of heme catalysis also has its problems. Chemical model systems use chelators, model hemes, and substrate structures that are quite different from those existing in foods. Reaction sequences change with heme, substrate, solvent, and reaction conditions. Intermediates are often difficult to detect (141), and derivations of mechanisms by measuring products and product distributions downstream can lead to erroneous or incomplete conclusions. It is no surprise, then, that there remains considerable controversy over heme catalysis mechanisms. Furthermore, mechanisms determined in these defined model systems with reaction times of seconds to minutes may or may not be relevant to lipid oxidation being measured in the complex matrices of foods stored for days or weeks under conditions where phospholipids, fatty acid composition, heme state, and postmortem chemistry complicate the oxidation once it is started (142). Hence, the mechanisms outlined below should be viewed as guides rather than absolutes. More research should be focused on determining, by kinetic and product analyses, which reactions actually occur and are of practical importance in specific food systems. 

There is also much talk about glucose, serotonin levels, and other chemical imbalances that may occur within the body. In many instances, specific food allergies are the prime suspect, including the use of food additives. There are problems with hormones and steroids (natural and injected or ingested) and with diethylstilbestrol (DES). And there are the environmental factors, weighed by Theron G. Randolph and Ralph W. Moss in An Alternative Approach to Allergies The New Field of Clinical Ecology Unravels the Environmental Causes of Mental and Physical Ills. 

The problems of choosing one of the several commercial enzymes for a specific food system application are (1) wide ranges in enzyme activities assayed by different methods, (2) batch to batch variability, (3) different pH and temperature profiles depending on the source, (4) activators or inhibitors necessary for the reaction, and (5) compatibility of combining two or more enzymes. ... 

Although the above variables limit the quality and shelf-life of foods, not all variables are equally important for all products. Hence the applicability of these variables to specific food groups is now considered briefly, to indicate where the opportunities exist for overcoming the problems by means of packaging treatments. 

DDT is highly toxic to fish (LC q for trout and blue gill, 0.002—0.008 ppm), and it is only moderately toxic to birds (oral LD q mallard 1300 and pheasant >2240 mg/kg). However, widespread bird kills have resulted from bioconcentration of DDT through food chains, ie, from fish or earthworms. A significant environmental problem has resulted from the specific effects of DDE on eggshell formation in raptorial birds where accumulation has caused decreases in shell thickness of 10—15%, resulting in widespread breakage. 

For example trace elements in milk powder are not consumed as milk, and moisture in transformer oil is not used in transformers, yet matrix reference materials based on milk are imported as food and are subject to health certification requirements and sometimes import quotas. Likewise a matrix based on oil is identified as fuel or lubricating oil and is both classified as a hazardous material and subject to mineral oil tax. These problems arise because RMs are frequently incorrectly classified by specific title of their matrix (as Reference Material of Trace Elements in Rice is classified as rice) and not as reference material which is the intended use. 

The MRLs are derived from data from supervised residue trials that are generally carried out in the context of food production. Specific conditions of feed production are not considered. Therefore, many practical problems for the official control of feed must be solved in future, e.g., application of transfer factors and the calculation of MRLs for mixed feed. 

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