Eloy, Susana

Gomes, Ana M. P.

Malcata, F. Xavier

Pereira, C. Dias

Pintado, M. Manuela E.

English

Repositório Institucional da Universidade Católica Portuguesa

Impact of Microfiltration on The Manufature of Goat’s Milk Cheese - Microbiological Studies M.Manuela E. Pintado*1, Ana M.P. Gomes1, Susana Eloy2, C. Dias Pereira2, F. Xavier Malcata11Escola Superior de Biotecnologia, Universidade Católica Portuguesa. 2Instituto Politécnico de Coimbra - Escola Superior Agrária de Coimbra. Portugal.mpintado@esb.ucp.ptACKNOWLEDGEMENTSINTRODUCTIONI IPortugal, as well as other Mediterranean countries, still maintains a significant volume of manufacture of traditional, raw milk cheeses. However, awareness of food safety issues has urged thecontrol of the microbial population in such raw cheese milk so that it may offer as high a quality as possible in attempts to guarantee the safety of the final product for the consumer. Heat treatment is generally used to perform such control; however, due to the alterations that it may promote in the milk components, microfiltration has alternatively been shown to be an alternative option for cheese manufacture. Cheese milk treatments performed to control detrimental microbial activities in cheese also have the potential to change milk properties which may be of value for the final product. It is well known that pasteurisation causes changes in cheese quality, mainly due to heat induced interactions of whey proteins with caseins (Lau et al., 1991). Microfiltration has proven to be a good option to cheese milk treatment when compared with pasteurisation showing similar reduction in microbial counts but improved quality of cheese (Beuvier, 1997). Our study was carried out so as to evaluate the effects of several pre-treatments of raw goat’s milk on the microbiological properties of cheese manufactured therefrom. MATERIALS AND METHODSI   REFERENCESBeuvier, E., Bertahaud, K., Cegarra, S., Dasen, ª Pochet, S., Buchin, S., Duboz, G. 1997. Int. Dairy. J., 311-323. K.Y., Lau, K.Y., Barbano, D.M., Rasmussen, R.R. 1991. J. Dairy Sci. 74, 727-740.RESULTS AND DISCUSSION  I IMilk processingThe retentate from microfiltration revealed the highest content for all groups (as expected), close to RM and Skimmed milk. Pasteurised cream showed the lowest viable counts not only because of by high lipids content, but also due to use of batch pasteurisation. Figure 3. Mean values of viable counts of  coliforms (a), Enterococcus(b), Lactobacillus (d) and Streptococcus (d) in MM, PM and RM cheesesthroughout ripening.Goat Raw MilkThe evolution of Enterococcusthroughout the ripening-period (see Fig. 3b) showed lower counts in PM cheeses (< 104) until the end of ripening, while MF cheeses exhibited the highest counts until 3 wk of ripening-decreasing slightly during the last stages. Raw milk cheeses  followed the same tendency, but higher numbers during the final period of ripening were reached; thus  possesses lower counts (2-3 log cycles) mainly during the first 3 weeks of ripeningPasteurization(72ºC, 50s)Samples taken at 1, 7, 15, 21, 28 and 45 dL. Ki+Bacteriological counts Mesophilic  counts (PCA at 30ºC )Coliforms (VRVGA at 37ºC)Staphylococcus aureus (BPA at 37ºC, colony confirmation)Pseudomonas (PA at 30 ºC, colony confirmation)Enterococcus (KAA, at 37ºC)Streptococcus (M17, at 30ºC)Lactobacillus (MRS, at 30ºC)Listeria monocytogenes (ISO 11290-2)Salmonella (Vidas bioMérieux)pH measurementFigure 2. Mean values of pH throughout ripening storage.No Listeria or Salmonella were detected in all samples assayed.Pseudomonas and Staphylococcus aureuswere only observed in the retentateRETM (results not shown).When compared with raw milk, samples of PM and MF milk (sampled from cheese vat and mantained at 4ºC)showed an important decrease in totalviable counts (ca. 2 log) and coliforms(ca. 2 log and ca. 3 cycles respectively) and  (see Fig. 1). Pasteurized milk showed higher levels of lactic acid bacteria than MF, except for Enterococcus.Figure 1. Mean values of viable counts of different microbial groups in MM, PM, RM, PC, MMPC, RETM and SM mantained 1 d at 4ºC.The evolution of coliforms throughout ripening (see Fig. 3a) revealed that PM and MM cheeses possess lower counts (2-3 log cycles), manly during the first 3 weeks of ripening reducing the difference during the last stages of ripening, (due to de lower aw). However, no statistical differences were observed between PM and MM.In terms of Lactobacillus (see Fig. 3c)  in PM and MM (mainly from starter culture), the high initial numbers decrease slightly until the 3 wk, recovering by the end of ripening period. On the other hand, Lactobacillus present in RM cheese  maintain higher levels in last stages. Streptococcus (see Fig. 3d), with high counts, followed an opposite tendency.45671 7 15 22 30 45Ripening period (d)pH unitsMM PM RMMicrofiltration(30-45ºC, 1.4 µm Membralox GP™)Skim milk(SM)Cream Pasteurization65ºC, 30 min.Pasteurized cream(PC)Microfiltered Milk(MM)Retentate(RETM)(MMPC)Pasteurized Milk(PM)Raw milk(RM)Cheese manufactureMicrofiltered milk with pasteurized cream(MMPC)Pasteurized milk(PM)Raw milk(RM)Inoculation with  0.001g/L of starter (EZALTM MA4002 2U)Coagulation with  a 0.5% (v/v) solution of 10% (w/v) cardoon flower, after addition of 0.5% (v/v)  NaCl and 00.02% (v/v) CaCl2Ripening at 12-14ºC and 85-90 % R.H. Experiments in duplicateSamples from each container were mantained 24 h t 4ºCbefore analysisThe work was supported by project nº 312 program AGRO/IED funded by Portuguese Ministry of Agriculture.0,01,02,03,04,05,06,07,08,09,0Coliforms EnterococcusLactobacillusStreptococcusviable counts (log (cfu/ml))MM PM RM PC MMPC RETM SMThere was a gradual and similar decrease in pH in all types of cheese throughout ripening period (see Fig. 1), with a final pH ca. 5.2, with no apparent statistical difference in the spite of microbiological differences between them. Microfiltration has prove to be a good alternative to pasteurisation in order to improve final microbiological safety of raw goat milk cheeses. These results will be correlated with sensorial and biochemical properties under study.a0,01,02,03,04,05,06,07,08,01 7 15 22 30 45Ripening period (d)viable counts (log (cfu/g))MM PM RMa0,01,02,03,04,05,06,07,08,09,01 7 15 22 30 45Ripening period (d)viable counts (log (cfu/g))a0,01,02,03,04,05,06,07,08,09,01 7 15 22 30 45Ripening period (d)viable counts (log (cfu/g))MM PM RMa0,02,04,06,08,010,01 7 15 22 30 45Ripening period (d)viable counts (log (cfu/g))MM PM RMView publication stats

Impact of microfiltration on the manufacture of goat’s milk cheese - microbiological studies

https://repositorio.ucp.pt/bitstream/10400.14/41457/1/PI_MFGOATMILK1_2.pdf

Impact of microfiltration on the manufacture of goat’s milk cheese - microbiological studies

Abstract

Similar works

Full text

Available Versions

Repositório Institucional da Universidade Católica Portuguesa