Malcata, F. Xavier

Rocha, João M.

English

Repositório Institucional da Universidade Católica Portuguesa

INTRODUCTIONBreadmaking is still much of an art, especially in those cases where no standard starter culture is deliberately added. One such type of bread, BROA, is widelymanufactured at the farm level in Northern Portugal following ancient manufacturing procedures; this sourdough bread is obtained from maize and rye flours mixedwith water and salt, and most chemical reactions that occur therein are brought about by adventitions microflora, which are passed from batch to batch. BROA isimportant from an economic point of view because of the large number of small farmers that depend considerably on this extra source of income for subsistence. It alsohelps fixating people in rural regions, thereby preventing extensive exodus towards urban areas.Empiric know-how has been transmited between generations, and a few technological changes have become standard practices. One such alterations is the way theproducers keep the sourdough for the next batch: today they keep more and more often the sourdough in a refrigerator. Note that, traditional BROA is notmanufactured on a daily basis, but depends on the current needs.One logical question is what happens to the wild microflora present in the sourdough as time elapses. Hence, samples of sourdough were taken throughout thepreservation period at 4ºC, for up to 6 d, and total viable counting was duly performed.This study has shown that the´general microbiological properties of sourdough remain essentially unchanged during refrigerated storage, so there are no importantchanges also during samples transportation from the producers until they reach control laboratory.RESULTS and DISCUSSIONMicrobiological Profile in Sourdough: Evolution During Refrigerated StorageJoão M. Rocha & F. Xavier MalcataEscola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, PortugalACKNOWLEDGEMENTSThe authors are grateful to several members of the Regional Directorate of Agriculture of Entre Douro e Minho (DRAEDM) and several local farmers for cooperation within the experimental program described. Financial support for author J. M. R. was provided by a Ph.D. fellowship within the programfor the Creation of National Infrastructures in Applied Science and Investigation (CIENCIA), administered by the National Board for Scientific and Technological Investigation (JNICT, Portugal). Partial financial support was received from PAMAF – IED (Ministry of Agriculture, Portugal) through aresearch grant entitled “Pão de milho: caracterização do processo tradicional de produção e melhoramento tecnológico”.EXPERIMENTAL METHODS- First Principal Component (PC1) explains 60% of the variance in the initial matrix,whereas the second Principal Component (PC2) explains the remaining 40%- PC1 and PC2 together describe the total variance in the initial matrix- It was possible to reduce the 22 initial variables to only 2, with essentially no loss ofinformation- Some clusters can be defined from the correlation circle plotted on axes 1 and 2 (orloading plot), e. g.:= PAB with TSYES, HA, MSE, YEDCA,Yeasts, PCAF and BPM, with correlationcoeficients (c.c.) higher than 91%, or either with MRS and YEDCA, Molds, with c.c.higher than 75%;= TSA with BPM, YEDCA,Yeasts, KF, MSE, M17 and HA (c.c. >90%);= BCM with LSA, RBCAB,Yeasts, Anayes and FM (c.c. >90%);= MacConkey and RCM (c.c. = 100%); and= KEAA with RBCAB,Molds (c.c. = 88%);- Variables from each cluster (with high positive or negative correlations) do not allow agood distinction for the objects studied, in terms of log(CFU/gsample)- Variables with low correlation could account for the axis that distinguishes the objectsstudied, e. g.: PAB and RBCAB,Yeasts (10%); PAB and ANAYES (-8%); YEDCA,Yeastsand LSA (-8%). However, the best two axis are obtained with the Principal Components(PC)- The closer a variable is to the axis and the circle, the higher the correlation with thatfactor (Principal Component) is. As observed, all variables placed in the circle border,which justifies the 100% variance of the initial variables- HA contributes fully to PC1; MSE, YEDCA,Yeasts, PAB and TSA contribute withvalues higher than 91%, and RCM and KEAA with values of -99% and -97%,respectively, to PC1- LSA contributes fully to PC2; BCM, RBCAB,Yeasts and ANAYES contribute withvalues above 95% tp PC1Correlations Circle on Axes 1 and 2 (100%)TSA, 30ºCPABYEDCA, YeastsYEDCA, MoldsRBCAB, YeastsRBCAB, MoldsBCMTSYESMRSBPMFMPCAFRCMM17LSAKFKEAAMSEHAANAYESMacC-1-0.8-0.6-0.4-0.200.20.40.60.81-1 -0.5 0 0.5 1Axes 1 (60%)Axes 2 (40%)Gram-RodsEnterobacteriaceaePseudomonasAcinetobacterAlcaligenesSalmonella; Shigella; Yersinia(and other facultative anaerobe coliforms)VRBDAPABHerella agarANAYESMacConkeyT=37ºC; 24h; anaerobioseT=30ºC; 48h; aerobioseT=30ºC; 24-48h; aerobioseT=30ºC; 24-48h; aerobioseT=37ºC; 24h; anaerobioseGroup Culture mediumConditionsGram+Rods Bacillus cereusBacillusClostridiumLactobacillusBCMTSYESRCMMRST=37ºC; 48h; aerobioseT=37ºC; 48h; aerobioseT=30ºC; 64h; anaerobiose T=30ºC; 64h; aerobioseGroup Culture mediumConditionsGram+CocciStaphylococcusMicrococcusStreptococcus (Lactococcus)BPMM17T=37ºC; 48h; aerobioseT=30ºC; 24-48h; aerobioseT=30ºC; 48-64h; anaerobioseGroup Culture mediumConditionsLactococcusStreptococcus (Enterococcus)LSAKFT=30ºC; 48-64h; anaerobioseT=37ºC; 48-64h; anaerobioseEnterococcusLeuconostocKEAAMSET=37ºC; 48-64h; anaerobioseT=30ºC; 48-64h; aerobioseFMYeasts and MoldsYEDCARBCABT=30ºC; 48h; aerobioseRoom temperature; 64h; aerobiose; darknessTotal Viable CountsTSAT=30ºC; 24-48h; aerobioseGroup Culture mediumConditionsSamples of sourdough were taken along its preservation period at 4ºC, and total viable counts were obtained after inoculation and incubation. In order to check for the existenceof a wide diversity of microorganisms, a large number of culture media and incubation conditions were selected, according to the schematic procedure shown below:Viable counts of Yeasts and Molds02468101 2 3 4 5 6Time (day)log(CFU/gsample)TSA, 30 YEDCA, YEASTS YEDCA, MOLDSRBCAB, YEASTS RBCAB, MOLDSViable counts of Gram- Rods 02468101 2 3 4 5 6Time (day)log(CFU/gsample)PAB HA ANAYES MacCViable counts of Gram+ Rods7.588.599.51 2 3 4 5 6Time (day)log(CFU/gsample)BCM TSYES MRS RCMViable counts of Gram+ Cocci0510151 2 3 4 5 6Time (day)log(CFU/gsample)BPM FM PCAF M17 LSA KF KEAA MSEMean log(CFU/gsample):TSA,30 - 8.6YEDCA, Yeasts - 7.6YEDCA, Molds - 5.1RBCAB, Yeasts - 7.2RBCAB, Molds - 5.8Mean log(CFU/gsample):VRBDA - 0PAB - 7.1HA - 8.8ANAYES - 8.7MacConkey - 4.6Mean log(CFU/gsample):BCM - 8.6TSYES - 8.8MRS - 8.8RCM - 7.9Mean log(CFU/gsample):BPM - 4.3 LSA - 9.4FM - 9.5 KF - 8.3PCAF - 8.6 KEAA - 8.3M17 - 8.3 MSE - 8.6Observations on Axes 1 and 2 (100%)126-5-4-3-2-101234-6 -5 -4 -3 -2 -1 0 1 2 3 4Axes 1 (60%)Axes 2 (40%)- The objects, in terms of number of storage days, are well dispersed, and can bedistinguished from one another by the culture medium- The general microbiological properties of sourdough remain almost unchanged duringtheir preservation at 4ºC, with no important changes during samples transportationfrom the producers to the laboratory

Microbiological profile in sourdough: evolution during refrigerated storage.

https://repositorio.ucp.pt/bitstream/10400.14/5404/1/com-inter_2001_ESB_361097001_Rocha_Jo%c3%a3o_15.pdf

Microbiological profile in sourdough: evolution during refrigerated storage.

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