Call number: LD2668 .T4 1930 S61

Call number: LD2668 .T4 1935 R61

Call number: LD2668 .T4 1938 M91

Numerous investigations have been made on the contribution of butter cultures to the flavor of cultured cream butter, but production of uniform cultured cream butter has not been possible in industry. Therefore, it was desirable to investigate in detail the qualitative and quantitative chemistry of the flavor of high quality butter cultures, and to examine more closely some of the aspects of flavor production by butter culture organisms. Volatile flavor components of high quality butter culture and control heated milk were isolated from intact samples by means of a specially designed low-temperature, reduced-pressure steam distillation apparatus. Most of the flavor compounds present in the resulting distillate fractions were tentatively identified by gas chromatographic relative retention time data. Flavor concentrates obtained by ethyl ether extractions of aqueous distillates were also separated by temperature-programmed, capillary column gas chromatography, and the effluent from the capillary column was analyzed by a fast- scan mass spectrometer. Many of the flavor compounds in the flavor concentrates were positively identified by correlation of mass spectral and gas chromatographic data. In addition, supporting evidence for the identification of some flavor components was obtained through the use of qualitative functional group reagents, derivatives and headspace gas chromatography. Compounds that were positively identified in butter culture include ethanol, acetone, ethyl formate, methyl acetate, acetaldehyde, diacetyl, ethyl acetate, dimethyl sulfide, butanone, 2-butanol, methyl butyrate, ethyl butyrate, methane, methyl chloride, carbon dioxide and methanol; also included were 2-pentanone, 2-heptanone, acetoin, formic acid, acetic acid, lactic acid, 2-furfural, 2-furfurol, methyl hexanoate, ethyl hexanoate, 2-nonanone, 2-undecanone, methyl octanoate and ethyl octanoate. Compounds that were tentatively identified in butter culture include hydrogen sulfide, methyl mercaptan, n-butanal, n-butanol, 2-hexanone, n-pentanal, n-pentanol, 2-mercaptoethanol, n-butyl formate, n-butyl acetate, 2-methylbutanal, 3-methylbutanal, methylpropanal, methyl heptanoate, n-octanal, 2-tridecanone, methyl benzoate, methyl nonanoate, ethyl nonanoate, ethyl decanoate, methyl dodecanoate, ethyl dodecanoate, delta-octalactone and delta-decalactone. Compounds that were positively identified in control heated milk include acetaldehyde, ethyl formate, ethyl acetate, 2-heptanone, 2-furfural, 2-furfurol, 2-nonanone, 2-undecanone, ethyl octanoate and methyl decanoate. Compounds that were tentatively identified in control heated milk include dimethyl sulfide, hydrogen sulfide, ammonia, methyl mercaptan, methyl acetate, acetone, methanol, butanone, butanal, n-butanol, methyl butyrate, ethyl butyrate, 2-pentanone, 2-hexanone, 2-mercaptoethanol, 2-furfuryl acetate, ethyl hexanoate, methyl heptanoate, 2-tridecanone, ethyl decanoate, ethyl dodecanoate, delta-octalactone and delta-decalactone. The data indicated that the qualitative flavor composition of control heated milk and butter culture were very similar. Diacetyl, ethanol, 2-butanol and acetic acid were noted to be consistently absent in the data for the control heated milk. Other compounds were not observed in the heated milk fractions, but were also absent from some of the culture fractions. This was attributed to their presence in low concentrations, chemical instability or inefficient recovery. A modified 3-methyl-2-benzothiazolone hydrazone spectrophotometric procedure was adapted for the determination of acetaldehyde produced in lactic starter cultures. The procedure was applied in conjunction with diacetyl measurements in studying single- and mixed-strain lactic cultures. The diacetyl to acetaldehyde ratio was found to be approximately 4:1 in desirably flavored mixed-strain butter cultures. When the ratio of the two compounds was lower than 3:1 a green flavor was observed. Acetaldehyde utilization at 21°C by Leuconostoc citrovorum 91404 was very rapid in both acidified (pH 4.5) and non-acidified (pH 6.5) milk cultures. The addition of five p.p.m. of acetaldehyde to non-acidified milk media prior to inoculation greatly enhanced growth of L. citrovorum 91404 during incubation at 21°C. Combinations of single-strain organisms demonstrated that the green flavor defect can result from excess numbers of Streptococcus lactis or Streptococcus diacetilactis in relation to the L. citrovorum population. Diacetyl, dimethyl sulfide, acetaldehyde, acetic acid and carbon dioxide were found to be "key" compounds in natural butter culture flavor. Optimum levels of these compounds in butter culture were ascertained by chemical or flavor panel evaluations. On the basis of these determinations, a synthetic butter culture prepared with heated whole milk and delta-gluconolactone (final pH 4.65) was flavored with 2.0 p.p.m. of diacetyl, 0.5 p.p.m. of acetaldehyde, 1250 p.p.m. of acetic acid, 25.0 p.p.b. of dimethyl sulfide and a small amount of sodium bicarbonate for production of carbon dioxide. The resulting synthetic butter culture exhibited the typical aroma, flavor and body characteristics found in natural high quality butter cultures, except that the delta-gluconolactone was found to contribute an astringent flavor. / Graduation date: 1965

No description available.

M.Sc. (Zoology) / Schilbeids or butter barbel represent a valuable source of protein for the people of Africa. Recently, several local producers commenced with the commercial production of butter barbel. To manage this resource and to provide a long-term sustainable yield, it is essential to have a thorough knowledge of the taxonomy, distribution, ecology and genetic structure of this species. By preserving the genetic structure of a species, erosion of its genetic variability is prevented, enabling them to adapt and consequently survive altering environmental conditions. However, several natural and anthropogenic influences acting upon the populations may affect their genetic variability and ultimately their survival ...

No description available.

Cocoa butter is a highly complex system of triacyglycerides which has been shown to crystallize in a markedly different fashion under the application of shear. A rheometer insert was developed to enable the intact extraction of sheared samples for study of melting properties, crystal orientation and breaking stress. Samples were created by ramping from 50°C at three different cooling rates (0.5, 1 and 2°C/min) to three different end point temperatures (16, 18 and 20°C), creating nine different temperature sets. Viscosities of the cocoa butter samples under shear were recorded during sample creation and large jumps in viscosity were identified as form II and form V crystallization. Comparison of crystallization times for the nine different temperature profiles allowed for the conclusion that over a shear range of 90 – 1000 s^-1 there was no further appreciable shear acceleration of the form V transformation for the 16 and 18°C temperatures and only a slight increase up to 500 s^-1 for the 20°C temperature. Sheared samples were also examined with differential scanning calorimetry. Samples were examined for peak melting temperature on each of day 0, day 1, day 7 and day 28. Six of the nine different temperature conditions examined yielded a critical shear rate, above which the melting points of the samples were dramatically different than for low shear and no shear samples. For the day 0 and day 1 samples, above 500 s^-1 the melting temperatures were ~2°C higher than for 360 s-1 and below. For the day 7 and day 28 samples, above 500 s^-1 the peak melting temperatures were ~2°C lower than for the lower shear and no shear samples. The orientation of sheared samples was also examined using x-ray diffraction. In all of the nine temperature sets, orientation was present for shear rates of 360 s^-1 and higher. Breaking stress measurements were performed on sheared and non-sheared samples. These tests showed results remarkably similar to those seen in the DSC tests, with a critical shear rate existing in six of the nine temperature sets, above which an increase in the breaking strength occurs. Examination of samples on either side of the critical shear rate with x-ray diffraction yielded two distinct x-ray patterns leading to speculation that the application of high shear rates causes a change in the crystallization of cocoa butter leading to selective crystallization and the formation of a compositionally different form V crystal with fewer defects than its lower/no shear counterparts.

Cocoa butter is a highly complex system of triacyglycerides which has been shown to crystallize in a markedly different fashion under the application of shear. A rheometer insert was developed to enable the intact extraction of sheared samples for study of melting properties, crystal orientation and breaking stress. Samples were created by ramping from 50°C at three different cooling rates (0.5, 1 and 2°C/min) to three different end point temperatures (16, 18 and 20°C), creating nine different temperature sets. Viscosities of the cocoa butter samples under shear were recorded during sample creation and large jumps in viscosity were identified as form II and form V crystallization. Comparison of crystallization times for the nine different temperature profiles allowed for the conclusion that over a shear range of 90 – 1000 s^-1 there was no further appreciable shear acceleration of the form V transformation for the 16 and 18°C temperatures and only a slight increase up to 500 s^-1 for the 20°C temperature. Sheared samples were also examined with differential scanning calorimetry. Samples were examined for peak melting temperature on each of day 0, day 1, day 7 and day 28. Six of the nine different temperature conditions examined yielded a critical shear rate, above which the melting points of the samples were dramatically different than for low shear and no shear samples. For the day 0 and day 1 samples, above 500 s^-1 the melting temperatures were ~2°C higher than for 360 s-1 and below. For the day 7 and day 28 samples, above 500 s^-1 the peak melting temperatures were ~2°C lower than for the lower shear and no shear samples. The orientation of sheared samples was also examined using x-ray diffraction. In all of the nine temperature sets, orientation was present for shear rates of 360 s^-1 and higher. Breaking stress measurements were performed on sheared and non-sheared samples. These tests showed results remarkably similar to those seen in the DSC tests, with a critical shear rate existing in six of the nine temperature sets, above which an increase in the breaking strength occurs. Examination of samples on either side of the critical shear rate with x-ray diffraction yielded two distinct x-ray patterns leading to speculation that the application of high shear rates causes a change in the crystallization of cocoa butter leading to selective crystallization and the formation of a compositionally different form V crystal with fewer defects than its lower/no shear counterparts.

A b s t r a c t. Shea nut butter was extracted from shea nut by cold press method and was investigated as feedstock for the production of biodiesel. Biodiesel yield was used to verify the optimization, while density and viscosity were chosen to serve as an indicator for the effectiveness and completeness of the ester conversion process. Based on the amount of shea butter used, the final product yield obtained was 94.55% mass and the percentage conversion of FFA in shea butter to biodiesel was 92.3% using a methanol/oil ratio of 6:1 and 1.0% mass KOH at 60 min and 55°C, respectively. The important properties of the biodiesel (density, kinematic viscosity, cloud point, pour point, cetane number, neutralization number, iodine value, methyl ester content and high heating value) were compared to those of ASTM and EN standards for biodiesel. The comparison shows that the shea butter methyl ester could be used as an alternative to diesel.