RESEARCH ments, thus aggravating the off-flavor problem. To determine h o w successfully various chemical additives minimize radiation damage, Short-ridge and coworkers tested a wide range of compounds on such foods as hamburger, sausage, haddock, corn, limas, peaches, and strawberries. Both treated and untreated samples of these foods were exposed to «-«^««« ^CtllUJUICI.
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(one rep being the absorption of about 93 ergs of radiation per gram of the material irradiated). The foods were subsequently odor-tested at room temperature by a trained five-member panel. Promising results were obtained with hydroxylamine hydrochloride. When previously treated with 0.005% of this compound, lima beans, for example, were found equally acceptable whether irradiated or nonirradiated. T h e panel also reported that corn treated with 0.0496 ascorbic acid plus 0.001% sodium nitrite and then exposed to 3 million rep is decidedly preferred t o corn similarly irradiated but without previous chemical treatment. Shortridge concludes: "While w e ourselves have not yet found an additive with a dramatically beneficial action on irradiation flavor, w e have found some compounds in our preliminary odor tests that have definite effects. Our main series of tests has little more than begun." • Srradiated Milk, Approximately 500,000 to 750,000 rep is sufficient for the practical sterilization of raw milk, says John H. Wertheim of MIT. T o guarantee complete sterilization under adverse conditions, such as high spore contamination, a dosage of at least 2 million rep is required. As other investigators have shown-, the threshold value for the recognition of irradiated milk is 20,000 rep for skim milk and 700O rep for -whole milk. Dosages of more than 50,000 rep produce little additional off-flavor. The off-flavors of irradiated skim milk are volatile, Wertheim points out. When irradiated skim milk is distilled under vacuum, the condensate, containing carbonyls and organic sulfides in the oxidized state, possesses t h e characteristic off-flavor. A. somewhat less volatile group of offflavors originates from the milk fats of irradiated whole milk and cream and has a n oxidative, rancid taste. Auother off-flavor originating from the milk fat is nonvolatile and has a chalky, metallic taste. These lipoidal offflavors are produced independently of «A,„ ~^.. r o>~ ^--nFree radical acceptors such as sodium ascorbate and ascorbyl palmitate are effective to some extent in reducing
off-flavors in irradiated milk. Irradiation in the frozen state substantially reduces off-flavors. However, trie extremely low threshold dose for milk offflavors necessitates development of other means for arriving at acceptable flavor levels. The characteristic off-flavor o f milk cannot be detected within 30 seconds after irradiation b y a heavy dose of
is irradiated with 2 million rep with simultaneous vacuum evaporation at 4 to 10 mm. H g , a significant decrease in side reactions takes place. All offnavor is removed except for some residual chalkiness. This chalkiness can be eliminated by increasing t h e operating temperature from 12° to 34° C. With the present method of opera_ _ »1- . JX _ *vl . _ii "r « i . rr cauiouc rays. /vniiusi an oi u i e orr- tion, says Wertheim, treatment with 2 flavor can b e removed by vacuum dis- million rep requires six hours. R e tillation of t h e milk soon after irradia- search is currently under way to speed tion. These and other observations up the process so that it can b e comhave suggested that the formation of pleted within a matter of minutes. H e "Although progress has been off-flavors probably proceeds in a chain adds: of reactions and that the time of forma- made i n the elimination of off-flavor tion o f off-flavors exceeds the half-life under certain conditions of irradiation, of free radicals b y several orders of it must be emphasized that it is n o t magnitude. Continuous removal of the yet known whether this method can volatile intermediaries interrupts the re- be modified sufficiently to have practiaction chain. cal commercial value." Tests at MIT show that, when milk
Microbes as Chemical Reagents Specificity of microorganisms for certain reactions in steroid chemistry gives new direction to research One program of the fermentation subdivision o f the Division of Agricultural and Food Chemistry was a daylong symposium on microbiological transformations and biosynthesis of steroids. It was t h e first such sympowhich would not sium devoted exclusively to this topic have been possible without microor- and the first, under the auspices of a ganisms, it is not surprising that the fermentation biochemistry or industrial industry is still financing large amounts microbiology group, to feature the subject, according to the chairman, Richof such research. In 1952, it became obvious that the ard W . Thoma, Squibb Institute for pharmaceutical industry was pouring Medical Research. Bacteria, yeast, and fungi (including considerable amounts of money into investigating microbiological processes the actinomycetes) are all capable of for transforming steroids. The reason transforming steroids in a number of was t h e severely competitive race for important ways. Bacteria, described by William a low-cost cortisone. The search for better ways t o pro- Charney of Schering, catalyze such reduce better cortisone-type materials actions as oxidation of secondary alcohas l e d to production of many other hols, hydroxylation, hydrolysis of esters, steroids of pharmacological interest. side-chain degradation, complete d e A s pharmacologists have gone t o work struction of the steroid nucleus P hydrodouble o n these newer steroids, still more in- genation of carbon-carbon terest has been generated in micro- bonds in conjunction with a ketone group, and dehydrogenation in ring A . biological methods. The characteristic of microorganisms T h e highly active glucocorticoids, predthat makes them so attractive i s their nisone and prednisolone, can b e pro(Corynebacterium specificity i n carrying out a certain re- duced by bacteria action with a iirinirnum of side re- simplex and Bacillus spharicus), which actions. A chemical reagent may at- introduce t h e double bond in ring A. Yeasts have been commercially i m tack a steroid in several places, extensively remodeling the molecule unless portant in reducing ketones and their the ixndesired reactions are blocked; action is said b y Charney to b e rethis involves extensive chemical manip- markably specific. Of the fu2i
