Frankfurters were manufactured to contain certain combinations of curing ingredients (sodium nitrite, sodium nitrate and DL alpha-tocopherol). Some frankfurters were made to contain in the finished product 0% added moisture, others were made to contain 10% added moisture, some frankfurters were not irradiated (0-megarad), others were irradiated with either 0.8 or 3.2 megarads (Cobalt-60 radiation source). Use of DL, alpha-tocopherol (at a level of 206 ppm) was associated with greater processing shrinkage, more off-flavor and less overall palatability (P<0.05). The most desirable external and internal cured color and firmest texture was in frankfurters made with 50 ppm of NO2 or with 100 ppm of NO2, irrespective of irradiation level. Use of irradiation (0.8 or 3.2 megarads) on frankfurters made without nitrite or nitrate did not improve visually determined cured color but did improve this color when determined spectrophotometrically; nevertheless, cured color of irradiated frankfurters made without use of nitrite or nitrate was not comparable to that of non-irradiated or irradiated frankfurters made with 100 ppm NO2. Irrespective of added moisture or curing ingredient combinations, significant differences (P<0.05) in palatability traits were associated with increasing irradiation levels (0, 0.8 or 3.2 megarads). Off-flavor increased, texture was less firm and overall palatability was less desirable as irradiation level increased. Low-dose irradiation (⩽1 megarad) may be feasible for enhancing the palatability traits of frankfurters containing lower levels of nitrite (lower than 156 ppm) but it appears that the correct irradiation level would be lower than the 0.8 megarad used in this study.

The influence of the environment on the formation of bacterial endospores has only lately been reviewed comprehensively and expertly by Knaysi (1948), and it would be superfluous to repeat the literature coverage, except where special points have direct bearing on the work presented here. The foregoing authority summarizes (p. 63) his views of the subject as follows: "The conclusion that an endospore is formed by a healthy cell facing starvation is undoubtedly true for all strongly aerobic members of BaciUus....." This representation, suggested also by earlier workers (see Knaysi's review, 1948), is frequently encountered. Viewed in a different sense, a spore may be thought of as the end product of a series of enzymatic reactions in the proper balance and integrated toward the generation of the spore. If this hypothesis is correct, any circumstance disrupting this balance would interrupt sporogenesis at any one of a number of stages in the biochemical sequence. Furthermore, such a disruption could be a function of the nutritional environment, a situation analogous to numerous other physiological processes in cells. The experiments reported below are not inconsistent with these ideas. Also established is the point that sporogenesis is independent of growth and that the latter may be abundant, healthy, and starved, and yet fail to generate spores. METHODS The strain of BaciUus cereus used came from the departmental collection. Its identity was confirmed by a positive phospholipinase test (McGaughey and Chu, 1948). To secure unambiguous results, uniform and homogeneous physiological conditions for all cells in the cultures were adjudged as being a prime requisite in work of this nature. Incubation of broth cultures on a continuous shaking machine accomplishes this objective. It also accelerates markedly the rate and increases the final total percentage of spores in the culture as compared to identical flasks incubated in the conventional stationary manner. This was true of all 8 species of Bacillus tested in many different media, and the data of table 1 are representative of the effect. Incubation always was at 30 C. Loop samples were removed daily for 4 days; films were prepared and heat-fixed in the usual way. The spores were stained green and vegetative cells pink by the malachite 1 This paper reports research undertaken in cooperation with the Quartermaster Food and Container Institute for the Armed Forces. The views or conclusions contained in this report are those of the authors. They are not to be construed as necessarily reflecting the views or having the endorsement of the Department of the Army.

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Frankfurters of twelve treatment combinations were made using a conventional manufacturing procedure. Manufacturing treatments included formulations of either 60% pork/40% beef, 100% mechanically deboned chicken (MDC) or 100% mechanically deboned turkey (MDT); sodium nitrite levels of 0 or 50 ppm; and sodium acid pyrophosphate (SAPP) levels of 0 or 3,750 ppm. Finished frankfurters were either not irradiated or irradiated at temperatures of either −34.4 or −51.1°C and at a dose level of 0.8 or 3.2 Mrad. Addition of SAPP did not significantly affect external or internal color, off-flavor incidence or overall palatability of any of the frankfurters but significantly increased processing shrinkage for pork/beef and chicken franks, decreased frankfurter pH values for pork/beef and chicken franks and improved texture of pork/beef, chicken and turkey franks. Addition of 50 ppm nitrite, as compared to use of no nitrite, significantly decreased processing shrinkage of turkey franks, increased batter and frankfurter pH of pork/beef franks, increased consumer cooking loss of chicken franks but decreased consumer cooking loss of turkey franks, decreased off-flavor of pork/beef, chicken and turkey franks, and improved internal color of pork/beef, chicken and turkey franks. An irradiation temperature of −51.1°C as compared with −34.4°C, decreased off-flavor intensity and increased palatability of pork/beef franks but did not affect other properties of pork/beef franks or any of the properties of chicken or turkey franks. Franks irradiated with 0.8 Mrad differed (P<0.05) from those that were not irradiated in only 3 of 18 sensory traits (including overall palatability of pork/beef franks); franks irradiated with 3.2 Mrad differed (P<0.05) from those which were not irradiated in 8 of 18 sensory traits (including overall palatability of pork/beef, chicken and turkey franks).

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