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Alkali extracted poultry protein obtained from mechanically separated poultry residues by aqueous extraction (pH 10.5) and acid precipitation (pH 5.5) was tested in all-chicken luncheon meats. The alkali extracted protein was included at 0–40% replacement for mechanically separated poultry used as the only meat ingredient. Texture measurements by Instron, drip loss and sensory evaluation data showed that the alkali extracted protein produced no significant differences in any of the luncheon meats at 20% or less replacement level. Differences in texture and flavour between the experimental products and a commercial all-chicken luncheon meat product were small even at the highest replacement levels used.

The shelf life at 25°C of chub-packed luncheon meat was inversely related to oxygen (O2) availability within the casing. With fibrous casings that are freely permeable to O2, shelf life was less than 3 d. With plastic casings of low O2 permeability, the shelf life was 7 d when air was trapped in the emulsion during the casing filling process, 14 d when air was not trapped (normal vacuum-stuffing) and greater than 28 d when vacuum-stuffed chubs were stored in hydrogen (H2). The initial spoilage bacteria, Bacillus spp., grew only at the surface unless air was trapped in the emulsion when growth occurred throughout the luncheon meat. Bacillus spp. failed to grow on luncheon meat stored under H2. Oxygen availability within the casing determined both the site and rate of microbial spoilage of chub-packed luncheon meat.

The relationship between sensory attributes and total numbers of bacteria was investigated in a study involving 600 samples of spiced luncheon meat. cooked salami, bologna, and chopped ham. The vacuum packaged products were purchased from 60 markets throughout the United States. Samples were subjected to microbiological and sensory evaluation within a few days after purchase and once a week during a 3-week refrigerated storage period. Based upon an off-flavor intensity scale of 1 = none to 7 = extremely strong, the samples having total plate counts (TPC) of< 104, 104, 105, 106, 107, and 108 per gram had mean taste panel scores (TPS) of 2.00, 2.25, 1.92, 2.06, 1.93, and 3.17, respectively over the 3-week storage period. A microbiological standard of 106 TPC would terminate shelf life of these products at 24–28 days after manufacture. Establishment of a total bacterial population of 108 per gram with a corresponding decrease in sensory quality did not occur until 46–60 days after manufacture.

A new approach to electronically counting microbial colonies is described. An experimental counter based on the theory, with no provision for calibration or setting of thresholds, returned counts comparing excellently with manual ones even in the presence of stained chicken, corn, tuna and luncheon meat debris, or highly coloured backgrounds of chocolate, paprika and turmeric. At the same time it accommodated illumination variations equivalent to at least four f-stops. In a few cases, where colonies were extremely difficult even for humans to distinguish, the counter returned poor counts; however, the new working principle permits it to alert the operator to the subject's dubious quality. The counter discriminated easily between two bacterial species on one plate, distinguishing and separately counting Aeromonas hydrophila (browny-yellow) and Citrobacter freundii (light yellow). It also identified and counted A. hydrophila in mixed culture by following the biochemical reactivity of colonies transferred across three substrates, counting only those which were positive on all three.

This paper deals with the application of optimal control theory to batch thermal processing of canned food to maximize the nutrient retention. A discrete state space model including those variables temperatures, nutrient concentration and lethal value is established for the thermally conductive canned food, and it has been verified in luncheon meat can, which is one of the thermally conductive canned foods. The relationship between the retort temperature taken as the control variable and the thermal destruction of different kinds of nutrients in food has been deeply studied for the conventional operation now widely used in canned industry, the optimal operations and the dynamic optimal control developed in this paper.

Canned shelf-stable luncheon meat containing varying amounts of sodium nitrite, prepared according to a commercial formula, was processed at 110°C to Fo = 0.4 and held at 35°C until nitrite was no longer detectable. The meat was then inoculated with spores of Clostridium botulinum separately heated to Fo = 0.4 and the cans were incubated at 30°C. Swelling of cans with concomitant toxin production was related directly to the size of the inoculum and inversely to the concentration of nitrite at time of manufacture. Meat containing 200 ppm of nitrite at time of manufacture (less than 2 ppm when inoculated) inhibited 1.43 log10more spores than meat that was manufactured without nitrite. It appears that an inhibitor, which we call Perigo-type Factor (PTF), is formed during commercial processing of shelf-stable luncheon meat that contains nitrite.

The stability of nine red food colours in pork luncheon meat products in the absence and presence of nitrite has been investigated. The extracted dyes were examined by visible and u.v. spectrophotometry and paper chromatography for changes due to processing and to the presence of nitrite. All the colours were destroyed to some extent but with nitrite more of the food colour survived. Subsidiary dye components and colourless fluorescent products were formed as a result of heat processing and in certain cases additional products were observed in the presence of nitrite.

When exposed to fluorescent light (250–1000 1x) at 4°C, luncheon meat containing erythrosine undergoes marked flavour deterioration in a few hours which is perceived mainly as a loss of flavour. The effect increased with light intensity and time of exposure but is absent in luncheon meat without added colours or with Red 2G in place of erythrosine. The results are consistent with the unique ability of erythrosine (amongst artificial food colours) to act as a sensitiser of photo-oxidation.

SUMMARY Study of the incidence of putrefactive anaerobic spores in fresh and cured pork trimmings and in canned pork luncheon meat from several commercial meat packing plants in Iowa indicated that the level of contamination was very low. The mode of putrefactive anaerobic spores in fresh pork trimmings was less than 0.18 per gram and less than 1 per gram in cured pork trimmings and canned pork luncheon meat. The maximum spore count found in any sample tested was 51 spores per gram. Spore counts on samples from different plants were similar.

Ground pork was inoculated with spores of Clostridium botulinum types A and B and thermally processed. Factors which affected toxinogenesis were the number of spores, the concentrations of sodium chloride (salt) and sodium nitrite, and the amount of thermal processing. Meat inoculated with 1 spore per g and processed to Fo = 0.6 became toxic if salt and nitrite were omitted. In contrast, meat inoculated with 106 spores per g remained non-toxic after the same thermal process provided sufficient salt and nitrite were present, i.e., with a brine (% salt in the aqueous phase) of 6.1% and no added nitrite, with a brine of 4.6% and 300 ppm of added nitrite, or with intermediate concentrations of salt and nitrite. The amount of thermal processing required to prevent toxinogenesis in meat with 146 ppm of nitrite and 5.5% brine depended on the concentration of spores. An Fo of 0.15 did not prevent toxinogenesis in meat inoculated with 104 spores per g; an Fo of 0.3 prevented toxinogenesis with 104, but not with 106 spores per g; and an Fo of 0.6 prevented toxinogenesis in meat inoculated with 106 spores per g. However, when the brine was decreased to 4.8%, meat with 146 ppm of nitrite and 106 spores per g became toxic even after an Fo of 0.68. Viable spores of C. botulinum were recovered 18 months after processing although the meat remained non-toxic, and normal in appearance and odour during this period. It is probable that some shelf-stable cured meats are safe because of the scarcity of C. botulinum in the raw product.

Heat penetration data on canned corned beef and luncheon meat are presented. The effects of can size, retort temperature and composition on process requirements and quality are demonstrated and discussed.

Changes in residual nitrite content of 18 sausage products during storage for various lengths of time are reported. Most pre-packaged processed meats (storage temperature 5 ± 2 C) showed decreasing residual nitrite levels during storage. All dried meat products (storage temperature 24 ± 1 C) showed increasing residual nitrite levels during storage. Residual nitrite decreased with cooking for the three products evaluated.

Canned pork of the type known as spiced luncheon meat was found to contain an appreciable amount of vitamin B1 after the complete canning process. There were, however, losses of the original vitamin B1 in the raw meat during the retorting process used for cooking and commercially sterilizing the product. These losses were 55.3%, 55.6%, and 41.9% of the original vitamin in three series of packs examined. It was possible to fortify 6-lb. export packs of canned pork with synthetic thiamin to a level equal to, or above, that of the natural vitamin in raw meat. The destruction of synthetic added vitamin was no greater than that of natural vitamin under the conditions of this study.

SUMMARY Under anaerobic culture conditions, 120 cultures of sporeforming rods were isolated from fresh and cured pork trimmings and from pork luncheon meat; 22 of these proved to be obligate anaerobic putrefactive organisms. Studied by the Reed and Orr method of rapid identification, the following species were identified: Clostridium. tetanomorphum, Cl. novyi, Cl. carnis, Cl. paraputrificum, Cl. tetani, Cl. histolyticum, and Cl. sporogenes. One culture was similar to Clostridium sp. National Canners Association putrefactive anaerobe 3679 (PA 3679). Serological relationships were determined by using antisera for Cl. sporogenes and PA 3679. No cross agglutination was obtained between Cl. sporogenes and PA 3679. An organism identified biochemically as Cl. carnis agglutinated in dilutions of 1:5120 of PA 3679 antiserum, indicating a very close serological relationship. Several organisms revealed antigens in common with Cl. sporogenes. The organism with biochemical reactions similar to PA 3679 showed no serological relationship to the known species. Serological relationships correlated with heat resistance while biochemical reactions did not.

Vacuum-packaged oven-roasted whole turkey breasts and sliced turkey breast luncheon meat are processed with and without potassium sorbate or sorbic acid. Through 12 days of accelerated storage at 10°C, the use of 0.26% sorbate reduced the psychrotrophic plate count in both products. In the main study conducted under commercial storage conditions of 4°C, the addition of 0.12% sorbic acid to the sliced product extended the time to reach 107 cells/g from 15 days in the controls to 42 days in the treated product. In oven roasted whole breasts, psychrotrophic counts in the controls were above 108 cells/cm2 after 14 days at 4°C while the sorbate pumped and dipped breasts were below that level through the 56-day storage period at 4°C. Organoleptic evaluations indicated no significant differences between control and sorbate-treated products.

The previously described headspace-gas chromatographic procedure for the determination of acrylonitrile (AN) in several foods, with N/P selective detection, has been modified to include packaged luncheon meats. The loss of AN during equilibration at 100°C in meat samples as well as the previously described loss in cold pack cheese and peanut butter has been studied. The loss of AN could be prevented by the addition of 10% phosphoric acid, which increases the acidity of the food-acid-salt slurry to pH 1.2-1.5. This acidification permits detection of AN at 2 ppb (5% FSD at 16 x 102 amp/mV) in all foods studied. AN was not detected in 10 samples of luncheon meat packaged in AN-based plastic which contained up to 2.6 ppm AN.

Growth of Clostridium botulinum from spores was inhibited in homogenates of luncheon meat produced commercially with varying amounts of sodium nitrite. The inhibition increased with increasing concentrations of nitrite present before the heating process but could not be accounted for by residual nitrite. It is concluded that a Perigo type inhibitor is formed during commercial processing of luncheon meat.

By using gas chromatography-mass spectrometry, seven volatile compounds were identified in vacuum-packaged sliced corned beef spoiled by Brochothrix thermosphacta under aerobic conditions. Acetoin and diacetyl appeared to be of major sensory significance.

Information is lacking on the ability of the common mold contaminant, Aspergillus flavus, to grow and produce aflatoxin in perishable foods at normal refrigerator temperatures. Because of public health interests we investigated the possibility of certain perishable foods contaminated with the mold developing an aflatoxin concentration under conditions of refrigeration. Cheddar cheese and luncheon-meat samples were inoculated with A. flavus ATCC 15517 and were refrigerated for 12 days at 4.4 or 7.2 C or incubated at 25 C for 12 days, Uninoculated cheese and meat samples were handled in the same manner. All samples were quantitatively analyzed by thin-layer chromatography for presence of aflatoxin. All samples; except those inoculated and incubated at 25 C, were negative for aflatoxin production. This indicated the mold would, not produce detectable aflatoxin in the tested foods when kept at normal refrigeration temperatures for 12 days.

The effect of different food textures on the replication of jaw movements has been generally ignored. In this study, the jaw movements of 28 young male subjects were measured while they chewed two samples of three foods—pork luncheon meat, dried apple and roasted salted peanuts. Several parameters, that characterized each chewing cycle when viewed from a frontal projection, were measured, and the average value for each variable was calculated. Values for dried apple and pork luncheon meat did not differ significantly between trials. However, for the second trial with peanuts, the chewing cycle duration was shorter (the duration of the closing phase being less and the closing velocity greater). These changes may have been due to exercizing caution during the chewing of a hard food while gaining familiarity with its texture.

The principal spoilage bacteria isolated from chub-packed luncheon meat stored at 25 °C have been identified as strains of Bacillus licheniformis and Streptococcus faecium. Bacillus licheniformis alone is responsible for those degradative changes (surface softening and discolouration, gas production and eventual product liquefaction) regarded as overt product spoilage. Streptococcus faecium metabolizes carbohydrate homofermentatively, and the resultant accumulation of lactic acid causes souring of the luncheon meat.

1. An outbreak of food poisoning due to S. typhimurium and S. thompson is described.2. These same two serotypes were found in trifle eaten by the victims.3. S. typhimurium was found in the stools of four members of the bakery staff and in the stool of one member of the grocery staff handling luncheon meat eaten by those affected.4. S. typhimurium was isolated from drains in the bakery.5. The phage-type of S. typhimurium found in the food handlers, drains, trifle and victims of the outbreak was the same.6. The phage-type of S. thompson found in the trifle was identical with that found in the victims of the outbreak.7. The phage-type of both salmonellae suggested an egg product source.8. It is surprising how infrequent these outbreaks are, having regard to the very frequent opportunity for the contamination of confectionery products in bake-houses.

Summary Spices and packaging materials were exposed to γ-irradiation at a dose of 10 kGy. Luncheon meat was prepared with irradiated or non-irradiated spices and packaged in irradiated or non-irradiated packaging materials. Packaged luncheon meat was treated with 2 kGy. Irradiated and non-irradiated packaged luncheon meat were kept in a refrigerator (1–4 °C) for 12 months. Microbiological, nutritive and chemical characteristics of luncheon were evaluated after processing and during storage; whereas, sensory quality was evaluated only after irradiation. γ-Irradiation decreased the microbiological counts of spices, packaging materials and packed products and increased its shelf-life. No significant differences in moisture, protein, fat, pH value, total acidity, lipid peroxide and volatile basic nitrogen were observed as a result of irradiation. Sensory evaluation showed that all the combinations of treated luncheon meats were acceptable. However, the taste, odour, appearance and texture scores of irradiated packaged products were significantly lower than those of non-irradiated samples.

Studies were performed to investigate the effect of combinations of mild heat treatment ( F 0 ≈ 0.5) and γ-radiation (4 kGy) on the microbiological stability of canned luncheon meat inoculated with spores of Clostridium sporogenes. The effect of heat treatment plus irradiation and that of a combination of the reversed sequence were studied. For quantification of the combined effect of the sporocide physical treatments and the inhibition of the survivors by the antimicrobial chemical factors (reduced a w , nitrite, suboptimal pH.) of the product, the method proposed by Hauschild et al. 0 J. Fd Protect . 48 (1985), 197) was followed. Storage studies demonstrated the increased efficacy of combination treatments against bacterial spores. Pre-irradiation followed by heat treatment resulted in higher spore damage/inactivation than the opposite order of treatment. It is estimated that the number of safe packages may be increased in the experimental batch treated by 4 kGy irradiation plus F 0 ≈ 0.5 min heat treatment than that of the batch which has been heat-treated only.