Progress 09/01/05 to 08/31/08
Outputs
OUTPUTS: In previous work we found that adittion of over 25% of whey affected the viscosity of the acid whey-milk fermented beverage. Fermented milk should have the viscosity and appeareance of a shake. Thus, fermented milk with 50% and 75% of whey did not have an appealing texture and viscosity. In order to improve the viscosity of the fermented milk we decided to use gelatin and pectin as stabilizers. Pectin manufacturer recommended an addition of 0.5% to 1%; however, after testing this level of addition we found the fermented milk chunky and not attractive. We reduced the level of addition of pectin to 0.2%. Gelatin was also tested as a stabilizer; initially the level of addition was 0.2%, which was too little and did not have an impact on the viscosity, thus we increased the level to 0.4%. Composition, titrable acidity, pH, viscosity, lactic acid bacteria and yeast counts were determined for the acid whey-milk fermented beverages. This experiment will be twice repeated. Further work to be performed are sensory and statistical analysis. Probiotic bacteria were isolated to be added to the acid-whey fermented beverage. At present, we are doing growth curves to determine the log phase of the isolated probiotic bacteria in order, to obtain enough cell concentration (109 ) incorporate to the acid whey fermented milk. Further work includes survival studies of the probiotic bacteria and shelf life determination. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
This work may lead into a possible use for acid whey, which at the current time is being disposed of, and represents a contaminant to the environment.
Publications
- Itara, L.O., 2007. Development of fermented acid whey beverage. MS Thesis. University of Puerto Rico, Mayaguez.
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Progress 09/01/06 to 08/31/07
Outputs
A. Volatile compounds determination using SPME/GC/MS The fermented milk-acid whey beverage was elaborated using with pasteurized cow's milk and acid whey. The acid whey was neutralized prior addition to milk to pH 6.5. The milk and whey were blended in the following proportions: 100% milk, 75% milk/25% acid whey, 50% milk/ 50% acid whey, 25% milk/75% acid whey and 100% whey. Commercial Kefir Starter (Body source) was added to the blended milk-acid whey as indicated by the manufacturer (0.5% inoculation) and incubated at 25 Celsius degree for 24 hours or until it reached a pH of 4.1. The samples were frozen at -10 C until chromatographic analysis. The volatile compounds and organic acids were determined by the technique of Solid Phase Microextraction using a Gas Chromatograph coupled to a Mass Spectrometer Detector. The volatile compounds found in all samples were ethanol, acetic acid, and 2, 3 butanediol at different levels. The organic acids that were found were
caprylic, caproic, caproic, benzoic and lauric acids. However no amounts of acetaldehyde, diacetyl and acetone were found, all of which are commonly found in fermented milk products. The highest amounts of ethanol (33.28%) and acetic acid (25.23%) was found on the fermented beverage manufactured with 100% whey and the lowest amounts of alcohol (9.25%) and acetic acid (8.59%) was found in the fermented beverage manufactured with 100 % milk. B. Viscosity of the Fermented Acid Whey Beverage The viscosity of the fermented beverages was measured with a Brookfield LVDV III viscosimeter. The most viscous was the fermented beverage manufactured with 100% milk followed by the fermented beverage manufactured with 75% milk/25% whey. The viscosity of the beverages were related to the percentage of total solids. The inclusion of over 25% acid whey to the fermented beverages has a negative impact on their viscosity. The utilization of a stabilizer may be considered to improve the viscosity of
fermented milk beverages manufactured with acid whey. C. Sensory Analysis of the Fermented Acid Whey Beverage For the sensory analysis, a test known as Two to Five was performed in the 100% milk and 75%milk/25% whey fermented beverages. Because of the nature of this test we selected those beverages that had similar appereance in terns of color and viscosity. A population of 20 people from the College of Agricultural Sciences participated on the test. Only 15% of the panelists were able to identify correctly the sample that was different. This test showed that the sensory properties of the two beverages were similar .
Impacts
This work may lead into a possible use for acid whey, which at the current time is being disposed of and represent a contaminant to the environment.
Publications
- Luis Omar Itara. The manufacture of a milk- acid whey fermented beverage. MS Thesis. University of Puerto Rico. Mayaguez Campus. (The examination for this work will be on November 27, 2007)
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Progress 09/01/05 to 08/31/06
Outputs
The fermented milk-acid whey beverage was elaborated by using pasteurized cow's milk and acid whey. The acid whey was neutralized before addition to milk to ph 6.5. The milk and whey were blended in the following proportions: 100% milk, 75% milk/25% acid whey; 50% milk/ 50% acid whey; 25% milk/75% acid whey; and 100% whey. Commercial Kefir Starter (Yogurtmet) was added to the blended milk- acid whey as indicated by the manufacturer (0.5% inoculation) and incubated at 25 Celsius degree for 24 hour or until it reached a pH of 4.1. Titratable acidity and pH was monitored during the incubation period. Once the pH of 4.1 was reached, the fermented milk-acid whey blends were refrigerated at 5 Celsius degree until analyses for % fat, % protein and % total solids were determined. Microbial enumeration, pH and titratable acidity was measured at the beginning and at the end of the incubation period. Viscosity measurement were also measured. Numerical differences were observed
for the different blends; however, statistical analysis needs to be done to determine whether there is significant difference among the treatments. Sensory analysis and volatile compounds need to be determined. Lactic acid bacteria to be characterized as Bifidobacterium for the incorporation in the acid whey fermented beverage as an adjunct culture have been isolated from two commercial sources. These include commercial yogurts claiming on their labels to contain lactic acid bacteria and Bifidobacterium and probiotic capsules sold in health stores claiming to contain lyophilized Bifidobacterium isolates in high and viable numbers. For the first commercial source, two products including Food Club Lite claiming to contain Lactobacillus acidophilus and Bifidobacterium spp., and Dannon Bifidus Regularis claiming to contain B. animalis were sampled. These yogurt samples were serially diluted in 0.1% peptone buffer and plated onto selective Lactobacilli MRS media and incubated at 37 Celsius
degree anaerobically (Gas Pak SystemTM) for 48 h. Lyophilized probiotic capsules (Kyo-DophilusTM, Inc.) were reconstituted in selective Lactobacilli MRS media and incubated under the previously described conditions and found to contain 9.4 x 109 CFU/g. A total of 49 isolates have been characterized on the basis of oxygen tolerance, colony morphology, cell morphology, gram staining reaction and catalase assay. The presence of the fructose-6-phosphate phosphoketolase (F6PPK), a unique enzyme expressed in the genus Bifidobacterium is used as a confirmatory result for the genus Bifidobacterium. A total of 23 isolates from the probiotic capsules and the yogurt samples have been assayed for the presence of the F6PPK and found negative (non-bifidobacteria). The remaining 26 isolates from one capsule trial with typical Bifidobacterium characteristics (catalase negative and Gram positive rods) have been secured in frozen stock collection in sterile 11% reduced fat milk and kept at -80 Celsius
degree as we await the arrival of a reagent (fructose-6-phosphate sodium salt) required for the continuation of the F6PPK assay. F6PPK positive isolates will be classified as Bifidobacterium and used as adjunct cultures.
Impacts
This work may lead into a possible use for acid whey, which at the current time is being disposed of and contaminating the environment
Publications
- No publications reported this period
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