Meat netting

Natural rubber has been the traditional material for elastomeric meat netting for many years and this has led to a number of studies into the levels of N-nitrosamines, nitrosatable and other compounds. Work carried out in the US A ° using a typical product produced from natural rubber latex contacted with a 50% ethanol simulant for 150 minutes at 152 °C produced the data shown in Table 12.5. 

Table 12.5 Levels of migrants found in 50% ethanol from meat netting...

A particular example of replacement technology that is associated with natural rubber involves the substitution of the use of tetramethylthiuram disulphide (TMTD) in field latex as a preservative with newly developed bacterial chemicals. As previously mentioned, TMTD is also commonly used as an accelerator and produces nitrosatable substances. The resulting latex can then be used to produce food contact products such as gloves and meat netting thread. 

Example 15.1 What will be the internal dimensions of a cold room to store 900 t of boxed frozen meat if the box size is 700 X 450 X 150 mm and the net weight 30 kg ... 

In a study with 40 healthy men and women, average age 63.7 years, who were randomized to either an alkali diet (meat plus fruits and vegetables) or an acid diet (meat plus cereal grains) (Jajoo and others 2006), altering the renal net acid excretion over a period of 60 days affected several biochemical markers of bone turnover and calcium excretion. The acidity of the diet had a significant effect on increasing NTX, a urinary marker of bone breakdown, and increasing the amount of calcium excreted in the urine. 

Volatile nitroso compounds were determined in hams processed in elastic rubber nettings by SPE and GC-CLD577. By a similar method A-n i tro sodi ben zy lamine (278b), a semivolatile nitrosamine, was determined in these products by SPE followed by GC interfaced to a nitrosamine-specific TEA-CLD detector the coefficient of variation was 10.6% at the 2.1 ppb level578. The nitrosamines detected in ham most likely originate from the amine precursors in rubber and from the nitrite commonly used in the meat curing process. 

The last source of NOC that has been a major source for health concern of infants is usage of rubber pacifiers and baby feeding bottles fitted with rubber nipples. NOC present in the rubber formulations can migrate into baby foods and drinks and into meat packed in rubber nettings. 

The countries of SSA produced 315 mio. t of the major food crops and 27 mio. t of meat and milk in 2003. Together with stock balances and net imports, 367 mio. t of food were available (PRB, 2005 FAOSTAT, 2006). While mean national dietary energy supply was above the required minimum in all but four countries (Burundi, Eritrea, Mozambique, Somalia) during 1996-98, actual food allocation caused an average 34% of the population to be malnourished (FAO, 2000 excl. South Africa). Despite an expected population increase to more than 1 billion people (PRB, 2005), average daily caloric intake is projected to rise from 2050 kcal in 1998 to 2500 kcal in 2030, partly due to expected increases in food imports (FAO, 2000). 

The use of plastic netting to hold and shape meat during curing resulted in the finding of N-nitrosodiethylamine and N-nitrosodibu-tylamine in hams up to levels of 19 ppb (parts per billion) (Sen et al. 1987). Later research established that the levels of nitro-samines present were not close to violative levels (Marsden and Pesselman 1993). 

BOUMA K and schothorst r c, Identification of extractable substances from rubber nettings used to package meat products , Food Additives and Contaminants, 2003 20(3) 300-307. 

U.S. Patent 4,434,187 (242) covers a meat curing composition that contains deoiled, powdered lecithin. The purpose of lecithin is this application is to prevent separation of the brine solution. Lecithin is also used in release agents for meat casings and nets. Hammer, et al. (243) recommended that an aqueous-based release agent for cellulose sausage casings, which contained 5-12% lecithin, be applied at a rate of 450-800 mg/m, based on the lecithin weight. 

A number of nitroso compounds, A-nitrosamines among them, are potent carcinogens. The most common carcinogenic nitrosamines, found mainly in protein food, are A-nitroso-dimethylamine (NDMA), A-nitroso-diethylamine (NDEA), A-nitroso-pyrrolidine (N-Pyr), and A-nitroso-piperidine (N-Pip). These compounds supposedly increase the risk of colon, rectum, stomach, pancreas, and bladder cancers. Nitrosamines are most prevalent in cured meats, but have also been detected in smoked fish, soy protein foods dried by direct flame, and food-contact elastic nettings. Dietary surveys indicated weekly mean intakes of these compounds amounting to about 3 pg per person (Anon., 1988 Cassens, 1995). In addition, the precursors of nitrosamines, especially nitrate, are abundant in some leafy and root vegetables (Table 14.1). 

Crystal-mediated cellular damage can take place during frozen storage due to temperature oscillations, resulting in a net increase in the crystal size (Martino and Zaritzky, 1988) this type of damage occurs more rapidly at the surface of meats (Devine et al., 1996). 

The isoelectric point of a protein is defined as that pH at which the net charge is zero (Wismer-Pedersen, 1971). Since protein-protein ionic interactions are promoted at this point, it would be expected that the protein matrix would shrink and WHC would be at a minimum (Kapsalis, 1975). It follows that increasing the pH away from isoelectric point would also result in a higher WHC, since protein-water interactions are favored (Hamm, 1960). Bouton et al. (1971) were able to increase the ultimate pH and WHC of meat by preslaughter injection of epinephrine and showed that tenderness increased directly with pH values. Further work by Bouton et al. (1972) and Bouton and Harris (1972) showed that as pH increased from normal values of 5.5 to 7.0, tenderness of the tissue increased and became independent of the contracture state. 

The radiolysis of food constituents leads to minor but sometimes perceptible changes in sensory qualities associated with the net formation or degradation of a specific constituent. Color, texture, and rancidity are qualities that can be affected either during irradiation or subsequent storage, depending on the food, the atmosphere, the packaging, and the irradiation dose and temperature. Often, there are implications in the radiation chemistry for ensuring optimal quality of irradiated meat products. 

The spectrum of surface active behavior displayed by food proteins directly reflects differences in structural and physicochemical properties among the proteins originating from various sources i.e. meat, milk, legumes. Chemical or enzymatic modification of model food proteins has indicated that alteration of specific structural features e.g. net charge, disulfide bonding, size, does influence film formation, foaming and emulsifying properties. 

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