OIL-IN-WATER CREAM STABILITY 219 values within the range of 230-280. No liquid bleed separation was observed in samples of cream after 24-month storage between -20øC and 40øC. Additionally, samples of cream packaged in tubes did not exhibit any liquid separation. Scale-up batch sizes of 50 kg to 200 kg were prepared successfully using planetary (Glen) type mixers equipped with variable-speed homogenizer agitators for emulsification. CREAM FORMULATED WITH U.K.-SOURCED RAW MATERIALS In consideration of worldwide manufacture of the cream product and as part of scale-up development evaluations to support the use of raw material sourced from other coun- tries, hatching studies were initiated using selected raw materials obtained from the United Kingdom (U.K.). A 20-kg placebo cream batch was prepared in a 10-gallon Groen mixer. The cream contained U.K.-sourced glyceryl monostearate, cetyl alcohol, Syncrowax ERL-C, Amerchol L-10! (oil phase components essential for gel structure and consistency), Tween 60 (emulsifier) and Glucam E-20 (humectant), which was soluble in the aqueous phase. All other ingredients in the cream were U.S.-sourced. The finished bulk cream immediately after manufacture had a soft fluid consistency and exhibited excessive liquid bleed when stored in tubes and when subjected to the wire- mesh bleed test. This was also obvious when pockets or crevices were made in the surface of the cream. A portion of the bleed was analyzed and found to contain mainly water and propylene glycol, which indicated that the external aqueous phase was not entirely entrappeal within the gel matrix of the cream. Also, the soft fluid gel consis- tency of the cream indicated the absence of a rigid gel structure, which may have been due to shear thinning or delayed gel formation. A comparison of the key differences between creams prepared using U.S.- and U.K.-sourced ingredients is summarized in Table I. EFFECTS OF STORAGE TIME AND TEMPERATURE ON CONSISTENCY AND BLEED POTENTIAL OF CREAM CONTAINING U.K. INGREDIENTS The cream batch containing U.K.-sourced excipients was subdivided on the second day after manufacture. Portions of the cream were placed in tightly sealed stainless steel containers and stored at 5øC, 24 ø + 3øC, and 33øC. Consistency and the extent of bleed were determined after 3, 6, and 17 days of storage. The results shown in Figures 1 and 2 indicate that warm temperature storage (33øC) for 3 days caused accelerated gel Table I Observed Differences Immediately Upon Manufacture of Cream Bases Prepared Using U.S. and U.K. Raw Materials Cream prepared using U.S. ingredients Cream prepared using U.K. ingredients Appearance Firm Consistency 282-288 Bleed (% w/w) 0 Finely dispersed spheres of internal oil- Microscopic wax phase Soft, flowable 315-320 8-12 Uniformly distributed spheres of clear aqueous phase interdispersed with internal oil-wax phase

220 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS •20 11o 290 280 270 260 240 I I I • '" I i I i I i I • I 0 2 4 6 B 10 12 14 16 nu,= (day,) Figure 1. Time dependence of the consistency as a function of storage temperature for cream prepared using U.K.-sourced ingredients. Data are shown for 5øC (+), 24øC ([•) and 33øC (•) storage tempera- tares. 10 7 6 nuE (d•y•) 10 12 14 Figure 2. Time dependence of the extent of bleed as a function of storage temperature for cream prepared using U.K.-sourced ingredients. Data are shown for 5øC (q-), 24øC ([2]) and 33øC (•) storage tempera- tares.