Investigation of Sustainability of Dairy Goat Industry by Innovative Method of Product Development
The main theme of the 2nd year’s research for this project was focused on the feasibility of frozen-storage of goat milk cheeses for later marketing. Impacts of freezing on storage stability and shelf life of commercial plane soft and Monterey Jack semi-hard goat cheeses were evaluated for determining the changes in organic acid profiles, sensory properties and microbiological characteristics. Freezing did not have any significant adverse effects on nutritional, organic acids, sensory properties, and generally reduced microbiological populations compared with the unfrozen control cheese samples.
1. To compare effects of freezing and thawing on organic acid profiles of plain soft and Monterey Jack goat cheeses with fresh ones stored at 4oC.
2. To evaluate the impact of freezing on the sensory properties and shelf-life of fresh soft and Monterey Jack goat cheeses.
3. To determine effects of freezing and thawing on microbiological characteristics of plain soft and Monterey Jack goat cheeses.
After almost 2 years delay, we finally have been able to hire two postdoctoral Research Associates for the project in March and May, 2002. For the 2nd year of the project, real studies have been implemented to accomplish the original goals described in the research project. We have launched to evaluate both soft and hard goat cheeses, after completing the past year¡¯s experimentation on the commercial soft goat milk cheeses for shelf-life and storage stability of refrigerated and frozen stored goat cheeses, as recommended by the project evaluating committee. Three batches of soft goat cheeses were purchased from a licenced goat Dairy in Georgia, and 3 batches of Monterey Jack hard goat cheeses were manufactured from the pilot plant of Fort Valley State University to evaluate the feasibility of freezing for extending shelf life of goat cheeses for later marketing and examine storage stability of the products with respect to chemical, nutritional, rheological, flavor and sensory characteristics.
The impacts of freezing on storage stability and shelf life of the plain soft and Monterey Jack goat cheeses were studied on three aspects: comparison of changes in (1) organic acid profiles, (2) sensory properties, and (3) microbiological populations of the products. Each lot of both cheese varieties was divided into two equal portions. One portion was immediately stored at 4oC and the other portion was immediately frozen (-20oC) and subsequently thawed the next day at 4oC and stored at 4oC. Organic acids were quantified using a HPLC (Hewlett Packard; LC-1100 Series) equipped with auto sampler, quaternary pump, vacuum degasser and diode array detector. The column was reverse phase Hewlett Packard ODS Hypersil 5mm (125 X 4 mm), and solvent was 0.5% ammonium phosphate. Descriptive sensory properties of the cheeses throughout 4 weeks storage (0, 14, 28 days) were evaluated with a trained panel. Flavors and tastes were scored on a 10-point Spectrum intensity scale. Changes in microbial populations were enumerated for total aerobic, E. coli and coliform, yeast and mold, and Staphylococcus aureus using 3M petrifilm techniques.
Freezing Monterey Jack cheese significantly (P<0.05) reduced lactic, orotic, citric acids, while butyric isomers significantly increased. Changes in other organic acids and their isomers in Monterey Jack were not significant, while a butyric isomer was in highest amount. Acetic and propionic acids in soft cheese were significantly (P<0.05) increased by freezing, whereas other acids were not significantly affected. Soft cheese had no pyruvic acid, while Monterey Jack contained no tartaric acid but several unknown large peaks appeared between propionic and butyric acids. After 2 weeks storage at 4oC, cooked/milky, diacetyl, and milkfat flavors decreased while yeasty and oxidized flavors increased in soft goat cheeses (P<0.05). Fresh soft cheeses had a sensory quality shelf life of less than 1 month at 4oC. Monterey Jack cheeses maintained sensory quality throughout 4 weeks storage at 4oC. Diacetyl flavors decreased and brothy flavors increased (P<0.05) while overall freshness scores did not change. Freezing had no effect on the sensory quality of either type of cheese throughout the subsequent 4 weeks refrigerated storage. No significant differences were found in microbial profiles between fresh and frozen-thawed cheeses for 4 wk storage, while total aerobic counts tended to decrease. E. coli, coliform, and Staphylococcus aureus in soft cheeses were non-detectable <1.0 (log cfu/g). MJ had E.coli and coliform, where fresh cheese contained higher than frozen ones, and they were reduced by aging within l (log cfu/g) deduction. Yeast counts tended to increase with aging in soft cheeses, but decreased in frozen MJ cheeses. Mold counts in both soft and MJ cheeses were similar at 3.0 (log cfu/g). On the other hand, we were not be able to conduct any economic analysis and marketing research on the goat cheese products through extensive consumer acceptability studies in order to determine the sustainability and profitability of dairy goat production.
Impacts and Contributions/Outcomes
It appeared that the outcomes of the research of this project for the 2nd year are crucially important, and could make extremely important contribution to the future sustainability of dairy goat industry. We have confirmed that freezing has not shown any noticeable deleterious effect on food quality and shelf life of the experimental cheeses, especially in lipolytic and proteolytic degradation of the products.
Freezing and thawing exhibited different impacts on organic acids contents of soft and Monterey Jack cheeses. Tartaric and propionic acids were important predictors for soft cheese, while pyruvic and butyric acids were for Montery Jack. Soft goat cheese exhibited a sensory shelf-life of less than 1 month, whereas Monterey Jack cheeses were stable through 1 month at 4oC. Freezing and thawing did not affect sensory quality of the two cheeses, which is important for feasibility of frozen-storage of goat cheeses. Freezing did not influence microbial profiles in both cheeses, whereas freezing and aging reduced E. coli and coliform. Soft cheese had negligible E. coli and coliform, while MJ had both cells, indicating that MJ might have been contaminated during processing.
The outcome of these results provide important beneficial information for development of goat cheese products, which will benefit for dairy goat farmers in the Southern Region as well as end-users including consumers, food scientists, members of Georgia Dairy Goat Breeders Association, and other interested clienteles. Through this research project, we also have provided visitors, consumers, other institution faculty and goat farmers with demonstration and training on goat milk cheese processing technology. Many groups from private sectors, school teachers and children, and especially college faculty and staff members have visited our milk processing facility. The results of the current investigation are being disseminated to the end-users, such as, and consumers through demonstrations, workshops and newsletters, and also to presentations in scientific conferences and publications in refereed scientific journals.
1. Park, Y.W. and L.N. Bell. 2002. Determination of Moisture and Ash contents of
Foods. Handbook of Food Analysis. 2nd Ed. Marcel Dekker, Inc. In Press.
2. Guo, M.R., Y.W. Park, P.H. Dixon, J.A. Gilmore, and P.S. Kindstedt. 2002.
Relationship between the yield of chevre and chemical composition of goat¡¯s
milk. Submitted for publication to Small Rumin. Research J.
3. Imm, J.Y., S.H. Kim, E.J. Oh, K.S. Han, S.J. Oh, and Y.W. Park. 2003. Functionality
and physico-chemical characteristics of bovine and caprine mozzarella cheeses
during refrigerated storage. Submitted for publication to J. Dairy Science.
Published Abstracts (Conference Proceedings):
4. Van Hekken, D.L., M. H. Tunick and Y. W. Park. 2002. Effect of frozen storage on
the proteolysis and rheology of soft goat milk cheese. J. Dairy Sci. Vol. 85. Suppl. 1; 254. Abst. No. 1017.
5. Park, Y.W., A. Kalantari, V. Gutta, R. Gundelly, and J.H. Lee. 2002. Comparison of
shelf-life of fresh and frozen soft goat milk cheeses in relation to the extent of proteolytic and lipolytic properties. J. Dairy Sci. Vol. 85. Suppl. 1; 255. Abst. No. 1022.
6. Kalantari, A. and Y.W. Park. 2002. Effect of frozen storage on microbial changes in
soft goat milk cheese compared with fresh ones. J. Dairy Sci. Vol. 85. Suppl. 1; 257. Abst. No. 1026.
7. Park, Y. W., A. Kalantari, and D. L. Van Hekken. 2002. Effects of Frozen and Fresh
Storage on Shelf-Life of Soft Goat Milk Cheeses. 2002 IFT Program Abstract No. 15B-17, p 22.
Ohio State University
Dept. of Food Science and Technology
2015 Fyffe Ct.
Columbus, OH 43210-1007
Office Phone: 6142927801
North Carolina State University
Raleigh, NC 27695-7624
Office Phone: 9195134596
Fort Valley State University
Agricultural Research Station
1005 State University Drive
Fort Valley, GA 31030-4313
Office Phone: 4788256827
University of Georgia
Dept. of Food Science and Technology
Food Science Building
Athens, GA 30602
Office Phone: 7065420994
Eastern Regional Research Center, USDA/ARS
600 E. Mermaid Lane
Wyndmoor, PA 19038-8598
Office Phone: 2158363777
Georgia Dairy Goat Breeder’s Association
1540 McRee’s Mill Rd.
Watkinsville, GA 30677
Office Phone: 7067699460