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Recently, the interest of consumers regarding artisan cheeses worldwide has increased. The ability of different autochthonous and characterized lactic acid bacteria (LAB) to produce aromas and the identification of the volatile organic compounds (VOCs) responsible for flavor in cheeses are important aspects to consider when selecting strains with optimal aromatic properties, resulting in the diversification of cheese products. The objective of this work is to determine the relationship between VOCs and microorganisms isolated (Lacticaseibacillus paracasei, Lactiplantibacillus plantarum, Leuconostoc mesenteroides and Lactococcus lactis subsp. hordniae) from raw sheep milk cheeses (matured and creamy natural) using accuracy and alternative methods. On combining Sanger sequencing for LAB identification with Gas Chromatography coupled to Ion Mobility Spectrometry (GC–IMS) to determinate VOCs, we describe cheeses and differentiate the potential role of each microorganism in their volatilome. The contribution of each LAB can be described according to their different VOC profile. Differences between LAB behavior in each cheese are shown, especially between LAB involved in creamy cheeses. Only L. lactis subsp. hordniae and L. mesenteroides show the same VOC profile in de Man Rogosa and Sharpe (MRS) cultures, but for different cheeses, and show two differences in VOC production in skim milk cultures. The occurrence of Lactococcus lactis subsp. hordniae from cheese is reported for first time

Aflatoxins of groups M and B have been investigated in 1150 samples of natural milk from Andalusian (Spain), collected during .the four sea-sons; in 330 samples of sterilized milk from 49 Spanish dairy centers, and in 77 samples of powdered milk (10 whole milk, 14 of skimmed milk and 54 of artificial mothers"milk). 15.2 p.100 of the samples of natural milk collected in winter contained M1aflatoxins; 8.5 p.100 of those collected in spring showed traces of M1 aflatoxin and only 0.17 p.100 of all the samples analysed contained B1 aflatoxin. The presence of aflatoxins was not detected in preserved milk. Se han investigado aflatoxinas de los grupos M y B en 1150 muestras de leche natural de Andalucía (España), recogidas en las cuatro estaciones del año; en 330 muestras de leche esterilizada procedentes de 49 centrales lecheras españolas, y en 77 muestras de leche en polvo (10 de leche entera, 14 de leche descremada y 54 de leche maternizada). El 15,2 p.100 de las muestras de leche natural recogidas en invierno contenía aflatoxinas M 1; el 8,5 p.100 de las recogidas en Primavera contenía trazas de aflatoxina M1; y solo el 0,17 p.100 de todas las muestras analizadas estaba contaminado con aflatoxina B1. No se detecto la presencia de aflatoxinas en leches conservadas.

A research was done on the evolution of the presence of yeast and moulds in yoghourt, which was kept at 7° C for 40 days. We have delt with 200 samples of two varieties: natural and strawberry flavour, both of them from two very well known Spanish makes. It has been checked the presence of yeast only in the natural variety. The presence of yeast evolves with no regularity. The contamination of yoghourt by moulds has been checked both in the natural and flavoured varieties. It does not increase but rather keeps at the checked level or decreases. A research was done on the evolution of the presence of yeast and moulds in yoghourt, which was kept at 7° C for 40 days. We have delt with 200 samples of two varieties: natural and strawberry flavour, both of them from two very well known Spanish makes. It has been checked the presence of yeast only in the natural variety. The presence of yeast evolves with no regularity. The contamination of yoghourt by moulds has been checked both in the natural and flavoured varieties. It does not increase but rather keeps at the checked level or decreases.

A quantitative and qualitative determination of present organochloride plaguicides residues has been carried out in 135 samples corresponding to 29 Spanish cheese types. All the samples contained residues. We have investigated 14 plaguicides***, the minimum number of plaguicides" per sample was one and the maximum eight, prevailing the samples which showed 3 and 4 plaguicides. The most frequent plaguicide was heptachlors total (68 9 p.100) followed by HCH total (77 p.100) and DDT total (68.9 p.100). Endrin and dieldrin have been found in a 37.8 and 15.6 p.100 respectively. All the samples threw lower average levels of pesticides than the ones recommended by FA0/OMS, except for heptachlore total which showed a content of pesticide two times over the limit allowed. In heptachlore a 19 p.100 of the samples threw levels higher than the ones allowed and in endrin a 13,7 p.100. Thus the levels obtained are similar or lower than the ones quoted in" other countries Se ha realizado la determinación cualitativa y cuantitativa de los residuos de plaguicidas organoclorados presentes en 135 muestras de 29 tipos de quesos españoles. Todas las muestras presentaban residuos: de 14 plaguicidas*** investigados, el numero mínimo de plaguicidas por muestra fue de uno; y el máximo, de ocho. Predominan las muestras de 3 y 4 plaguicidas. El plaguicida mis frecuente fue el heptacloro total (97 p.100) seguido del HCH total (77 p.100) y del DDT total (68"9 p.100). El eldrín y el dieldrín se presentaron en el 37"8 y el 15"6 p.100, respectivamente. Todas las muestras dieron en todos los pesticidas niveles medios por bajo de las recomendaciones de la FAO/OMS, salvo en heptacloro total .que arroj6 un resultado mis de dos veces superior al limite. En heptacloro, un 19 p.100 de las muestras presentaba niveles superiores al limite; y en eldrín, un 13"7 p.100. Los niveles obtenidos son iguales o mis bajos que los publicados por otros países.

We have done a research work on the evolution of the presence of coliforms, E. coli and enterococci in yoghurt which was kept at 72 C for 40 days. We have dealt with 100 samples of two varieties: natural and strawberry flavour yoghourt, both of them from a very well known commercial make. It ..has also been measured the pH and acidity of them. It has been checked the presence of coliforms and of E. coli, and in ten days time, we have noticed their extinction which was due to a higher level of acidity. We agree with Ale sieva (3) in the fact that research on coliforms and E. coli in yoghurt as a proof of its hygienic quality should be done not later than 24 hours after its process of elaboration finished. It has also beer checked contamination by enterococci, which persisted throughout the wole period of controlled conservation. Consequently, we think that search on enterococci in yoghourt as a proof of its hygienic quality t".hroughout its time of commercial life is amore appropriate than search on coliforms and E. coli. Se ha investigado la evolución de la presencia de coliformes, E. coli y enterococos en yogur conservado durante cuarenta días a 7-° C, en 100 muestras de dos variedades elaboradas en España: natural y sabor a fresa, pertenecientes a una marca de gran difusión comercial. También se ha medido el pH y la acidez. Se ha constatado la presencia de coliformes y de E.coli comprobándose, a los diez días de conservación, que resultaba inhibida a consecuencia del nivel de acidez alcanzado; por ello se coincide con Aleksieva (3) en que la investigación de coliformes en el yogur, incluido el E.,coli, como indicadores de su calidad higiénica, debe de realizarse no más tarde de veinticuatro horas desde que terminó de elaborarse. Se ha evidenciado igualmente una contaminación por enterococos que persistió durante todo el periodo de conservación controlado. Por ello estimamos que la búsqueda de enterococos en el yogur es más adecuada que la de coliformes y E.coli, como indicadores de su calidad higiénica, durante todo el periodo de vida comercial.

The evolution of the essential microflora in yoghourt kept at 72 C for 40 days,has been investigated in 300 samples belonging to two varieties, natural and strawberry flavour, from 3 well-kanown Spanish commercial makes. The pH and the acidity have been measured. It has been noticed that S. thermophilus and L. bulgaricus suffer a decrease in quantity, which is statistically significant (p 1O.OO1). In thirty days time this microflora was reduced to its 50 p.100; there being no relevant statistical differences between S. thermophilus and L. bulgaricus throughout this period of time. It has also been checked that the evolution of the essential microflora is related to variations of acidity of the yoghourt We propose th%t natural and flavoured yoghourts should contain a minimum of 100 x 10 bacteria per gramme both of S. thermophilus and of L. bulgaricus, and that the time of commercial life of yoghoyr"t kept at 72 C should be of 3 weeks since the end of its elaboration. Se ha investigado la evolución de la microflora esencial del yogur conservado durante cuarenta días a 72 C, en 300 muestras de dos variedades elaboradas en España (natural y sabor a fresa) pertenecientes a tres marcas de gran difusi6n comercial. Se ha medido también el pH y la acidez titulable. Se ha comprobado que el S. thermophilus y el L. bulgaricus experimentan un descenso numérico que es estadísticamente significativo (p0,001). A los treinta días de conservación esta microflora se había reducido en un porcentaje próximo al cincuenta por ciento y no existían diferencias significativas entre el S. thermophilus y el L. bulgaricus. Igualmente, se ha constatado que la evolución de la microflora esencial esta relacionada con las variaciones de la acidez titulable. Como consecuencia de la investigación se propone para el yogur, naturad l y aromatizado, que dichos productos contengan un mínimo de 100 x 10bacterias esenciales por gramo., tanto de S. thermophilus como de L. bulgaris, y se estima que la vida comercial del yogur conservado a 72 C es de tres semanas, contabilizadas a partir del termino de su elaboración.