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INDUSTRIAL AND ENGINEERING CHEMISTRY
Many rust inhibitors precipitai e t o foriii colloidal dispersions \\,lien subjected to low temperatures, and they may or mag not redissolve when exposed to higher temperat~ures. Addit,ive-: vhich appear to be in solution in oils are often in a metastable vonditiori and a change of teinperature or a violent mechanical disturbance can initiate precipitation. Therefore, low temperature solubility tests must last a t least 48 hours and must includi: frrqucnt agitation of the fluid. It has been shown earlier that the compounds most suit,abla for polar-type rust inhibitors should bc as high in iriolecular weight, as possible in order to dccrt,ase the solubility in water and with it the rate of leaching. fiut increasing the moleculai~ \wight in any homologous series will rimdl in a decrease in the Lsolubilityin the oil of high rno!rxnilar weight compoundq, a,nd herict: such inhibitors would rarely be sufficiently soluble in oils at low temperatures. I n inhihitirig fluids for use a t low teinperai u i w a compromise must be madix i n helaiiciiig the need for low i ctriipwature compatibility of the inhibit,or with the highest powible degree of rust inhibition. Uiilcas very surface-reactivc: arl(litivcs are used, or unless cloutliiig due to precipitation is :illo~ri:dat the lowest temperatuw, Ihere appears to he little hope 01' irihibit iiig a lov temperature oil against such severc conditions H S arc rcproduced in t,he fog and humidity cabinet tests:. Solubility problems are encounttlrect in preparing highly iiilribited oils. The low temyernturct solubility is usually assunied :ttlcquat~cif the inhibit,ed fluid mercly forms a faint haze or cloudiiiess during the low temperature stor.2tg.c' test, t i i d if the cloudiness disappears as the temperature returris to normal. 13c:cau~etho static water drop corrosion test \vas reproducible a n d rcquirctl only 20 1111. of oil per test, it offertd x convenient meihod of follmvirtg the changes of the rust inhibition of ail oil during storapii. of 0.2% calcium phcnylThe first, coniposit,ion studied co itcarate and 0.25% 4-ferf-butyl iylphcnol as antioxidant, i n highly purified di-(2-ethylhexq-l) ~ e b a c a t e . No rusting ocrurred in 168 hours a t 140" Ii'. iii t'ho static drop t'est oil thc: fi,tahly prepared fluid. After storage for 6 months in a cltwi covered bottle vhich was maintairir~dat 20' t'o 30 C. in the tiark, tht: same test showed slight rusting in 24 hours and serious rusting in I68 hours. After storage Tor o i i r yew, some rusting occurred Tritliin the first 24 hours (of c : x p o s ~ ut o~ ~the tevt') and it wa i n 48 hours. Similar tests were matlt. on sovrral newly purcha,sed s:tniplw of commercial rust-iiihihitrd ortlnarice petroleum hytlrttulic oils (specificatioris OS 1 I 13 :tnd O S 2943). Tlie latt,er oil dho\i-ed no rusting i i r 168 h r n u w , \vIii!c t l t t L rormi*r pc:~miitcvl
Vol. 41, No. I
iiig in 144 hours of exposuie or tlic r i w oil. A\tttlr itoiagil tor months in the original container, the OS 1113 ob failed aftei 4X lioius of the test while the OS 2943 oil failed after 96 hours. l I ' ( c > i rtoiage for one year the foriner oil failed within 24 houru ot l l i i s twt and the latter within 48 hoiira. Still ansthci exampl(~ IS that of a commercial petroleum ailcraft. txngine Errsrrvativc oil (.pccification .1N-VV-C-676a) mliioh w a ~iaixcd in the recomrnenclcd proportion3 of 1 part compound and 3 parts NS 1120 oil. 'l'he fog cabinet test a t 120 P'. rcwalrd that rusting coiiiiiiriircod with this oil after 144 hours of exposuit'. E'olloiiing b r11onths of storage of the oil, it failed in the 'og cabinet tcit :ti t c x i 72 hours, while after one year of storage i t failed in 48 hour.. 1 h . h one of these oils was oi,iginally clear t p the nttked e w , nor1 no mole Tyndall effect wab widciit ~ i t l ,.ihite i light thai. T I ctuld be caused by the oil without additive. I n each iristaiico x tainl haze viliose density appeared to incrclaae toward the bottom of thr contaiiwr hecame evident aftw the oil had bren storrd lor oiw pear. A t that time a strorig Tyndall effect was evidcnt Thi. proprrl v of storage instabilitv and the asqoriatd colloidal pht~ttornena are fundamental in the applicatioii and fut i i t Iopini~tltIJt polar-type inhihitov. and nwdq irivc~~tig:&lioli O
t b
ACKNOWLEDGMENT T t i c aut,Iiors are indebted to C. M. Murphy for his irit,crest ani1 ,suggestioiis arid to It. 0. Llilits arid J. E. Brophy of t'his lahoratory for. mechanical engineering rtdvicct iri designing the spociinrnf o i ~ i n i i i xtriachine and the rotating t,ahle s~icviriit?ii lioliii\ done o i l i t n nliquot of a 6-can sample and one on a 12-can sample.
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a Each figure represents the average from analyses of 3 packs: aiidysis done on an aliquot of a &can sample. b Each figure represents the average from analyses of 2 packs; nnalysis done on a n aliquot of a 6-can sample.
each
each
TABLU11. ASCORBIC ACID AND THIAMINE RETENTION OF CANNED ORAXGEJUICE, GRAPEFRUIT JUICE AND SEGMENTS, AND l'IND4PPLE JUICE AND SLICES, STORED 18 AND 24 LfONTHS AT THREE TEMPERATURES Retention i n Canned Food, % GrapeGrapePinePinefruit fruit apple appleo Or?nge juicea juireb segments' juice" slices Ascorbic ilcid 50 96 93 94 108 80 84 84 86 106 81 l8 65 62 62 57 90 59 80 95 94 87 108 83 24 50 80 82 77 100 78 65 60 57 46 79 53 80 Thiamine 105 .. 99 98 106 50 18 103 .. 100 94 96 65 89 85 .. 95 82 80 101 103 99 102 60 24 100 103 94 94 .. 65 93 83 84 .. 89 80 each a Each figure represents the average from analyses of 2 packs; arialysis done on a n aliquot of a 6-can sample. h Each figure represents the average from analyses of 3 packs; eacb analysis done on a n aliquot of a 6-can sample. c Six cans from one pack were mixed for analysis. Storage Temp, .\fonths F.
was a decrease in the carotene content of peaches, except those stored a t 50" F. for 18 months, and in whole tomatoes held 18 inonths as compared with 12 months, and a further decrease after storage for 24 months. The effect of temperat,urc on carotene was not, striking. S'iaciri was retained very well (96 to 100%) in peaches stored for 18--24 months in the constant temperature chambers. It was not retained quite so well in whole tomatoes and tomato juice, which lost 8 t o 15% of their original niacin contciit, during storage for two years. Losses of riboflavin were 2 to47, from whole tomatoes stored for 2 years at 50" to 80 O F. and 6 to 8% for tomato juice. Analytical difficultieii in the riboflavin assays, due to lack of precision of the method arid t o the low riboflavin contcnt of tomatoes, were mentioned in the previous paper. Losses of thiamine in foods stored 2 years a t 50' and 65 O F. werc small, not exceeding 1370. Losses were definitely higher, ranging from 7 t o 30Oj,,in foods stored 2 years at 80" F. than in those held at the lower temperatures. As with ascorbic acid, losses of thiamine seemed t o depend more on temperature then on time of storage. The thiamine content of orange juice and tomatoes held in the two warehouses having an average temperatsure of 77" F. was somewhat, lower than of t,he same foods held in cooler warehouses. Retentions were lower in the warehouse samples held 24 months than in those held 18 months.
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ilices stored 18 months, retentions were lower at 65 than a t 50 O F., and still lower at 80" F., ranging from 46 to 79% after storagc for 2 years at the highest temperature. As during the first 12 monthb of storage, temperaturt: seemed t o have more effect than the storage period on losses of ascorbic acid. The ascorbic acid retention of 84% for grapefruit juice held a t 65" F.for 18 months agrees rather closely with thc 81% retention obtained by Lamb ( I ) for grapefruit juice held for the same period a t 70" F. I t should be mentioned t h a t grapefruit juice stored 2 years was unpalatable. The warehouse samples also show a relationShip bet ween temperature and ascorbic acid retention, since orange juice and tomatoes stored in warehouses having high average storage temperatures retained less ascorbic acid than those in storage at lower temperatures. Carotene retentions were good (94 to 98%) in tomato juice held at all three constant temperaturw for 2 years. However, there
SUkIM4RY
A. duiirig the first 12 months of storage, clrvsted storage temperatures accelerated losses of ascorbic acid and thiamine more than did extended storagc periods. This was evident in the warehouse samples as well as in those stored in constant temperature chambers. Carotene retentions in tomato juice were excellent throughout the storage period. In whole tomatoes and in peaches losses were greater after storage for 24 than for 18months. Retentions of niacin were excellent in peaches and good in tomatoes and tomato juice stored for two yeard. Riboflavin W R retained very well in tomatoes and tomato juice. ACKNOWLEDGMENT
This work was supported in part by a grant from the h-ational Canners Association-Can Manufacturers Institute Nutrition Program. LITERATURE CITED
(1) Lamb, F. C.,IND. ENG.CHEM., 38,8804(1946). (2) Moschette, D. S., Hinman, W. F., and Halliday, E. G., Ibid., 39, 994-9 (1947). RFCEIVED October 31, 1947.
This is the twenty-sixth of a series of papers dealing with the general subject "Nutritive Value of Canned Foods."
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