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Natam=
ycin In
Ripening Cheeses Arnold Reps , Lucjan J“drychowski , Jan Tomasik=
,
Krystyna WiÑniewska1 2 1 1 1Institute of Food Biotechnology, University of
Warmia and Mazury in Olsztyn 2Institute of Animal Reproduction and Food Resea=
rch of
Polish Academy of Sciences, Olsztyn Abstr=
act: Natamycin 50% In Lactose is a preparation
containing the natamycin, a substance used in the therapeu=
tics, is used in cheese making to
protect a cheese surface against mould development. This preparation is a=
dded
either to polyvinyl acetate (PVA) used for cheese coating or as an aqueous
suspension in which cheese is immersed before the ripening. The natamycin
content in the outer layer of cheese was determinated by a spectrophotome=
tric
method. During maturation of cheese coated with natamycin-containing
polyvinyl acetate, the natamycin did not migrate into the cheese. The
natamycine concentration in cheeses that had been immersed in an aqueous
solution of natamycin was considerably higher than that in PVA-coated che=
eses
and was related to the type of cheese, concentration of the "Natamyc=
in
50% In Lactose" preparation, the length of time for which the cheese=
was
held in solution. Key W=
ords: Cheese, natamycin, migra=
tion
into the cheese, mould development Introduction Environmental conditions prevailing during cheese ripening, combined with the composition of the cheese often create possibilities for extensive development of mould on cheeses surfaces, which reduces considerably its quality. As a result of mould growth, aflatoxins may be produced in cheese, rendering it unfit for human consumption (Kiermeier a= nd Zeier, 1975; F.I.L., 1977). Therefore, during ripening, cheeses are prote= cted against development of mould by coating of their surfaces a protective la= yer. The use of "Natamycin 50% In Lactose" (Gist Brocades NV), containing 50% natamycin has considerably facilitated protection of chees= es against mould growth during ripening. "Natamycin 50% In Lactose" may either be added to brine, used as an aqueous suspension for dipping of cheeses or added to polyvinyl acetate used to coat the cheese. Natamycin,= at a concentration considerably lower than other known fungicides, destroys = both mould hyphae and spores (Moll, 1966; Shahani et al., 1985). Until now, cheeses have been protected against mould growth by treatment with propio= nic acid (Kujawski et al., 1983), sodium, calcium or potassium sorbate (Moll, 1966; Lück, 1972; 1975). The inhibitory concentration of sorbate is as h= igh as 300 mg/dm² of cheese surface while the permissi= ble concentration of natamycin is only 2 mg/dm² (WHO, 1976). Sorbate dif= fuses into cheese and affects its organoleptic properties (De Ruig and Von Der Berg, 1985) whereas the migration of natamycin is negligent, and when use= d in polyvinyl acetate, it remains on a surface of the cheese (Kiermeier and Zeier, 1975; Reps et al., 1987). Because natamycin is used as a hu= man medicine, it is necessaryto determine its concentration in various types = of cheese and the rate of its decay. In the present study, the suitabilit= y of "Natamycin 50% In Lactose" for Inhibition of mould on cheese surfaces was investigated. The experiments were made on Salami (Tilsit ty= pe cheese) and Jeziora½ski (Münster type cheese) cheeses ripened on = dry surface for four weeks. Material and Methods <= /p> To determine the suitability of "Natamycin 50% In Lactose" as a fungicide forcheese, cheeses were subjected to= one of the following treatments: * Cheeses Salami and Jeziora½ski were= dipped into 0.2 and 0.4% aqueous suspension of the preparation for 60 sec, before brining. * Salami and Jeziora½ski chee= ses were salted in brine containing 0.2% "Natamycin 50% In Lactose". * Salami and Jeziora½ski chee= ses were immersed for 30 and 60 sec in a 0.2 and 0.4% aqueous suspension of "Natamycin 50% In Lactose" after brining. * In order to examine an influence of cheese rind on the natamycin content in the outer layers of the cheeses, standard Salami cheese and Salami with the rind removed,were immersed for= 60 sec in a 0.4% aqueous suspension of "Natamycin 50% In Lactose".= * Gouda = type cheeses were immersed for 30 sec in a 0.2% aqueous suspension of "Natamycin 50% In Lactose" and packed in Cryovac bags while wet= or after drying the surface. Cheese was also packed in bags which had been dipped in a 0.2% aqueous suspension of "Natamycin 50% In Lactose&quo= t;. * Edam cheeses, after brining, were co= ated with one, two and three layers of polyvinyl acetate containing 0.1% of "Natamycin 50% In Lactose". After one week of ripening, half of= the cheeses from each lot were covered with cheese wax. During t= he ripening of cheeses, the effectiveness of antifungal action of natamycin = was observed (compared to the control cheeses) and its concentration in five consecutive, 1 mm-thick layers of cheese was determined, by the spectrophotometric method (De Ruig and Von Der Berg, 1985) Results and Discussion In cheeses, that had been immersed i= n and aqueous suspension of "Natamycin 50% In Lactose" before brining= the concentration of natamycin on the surface of cheeses was insignificant (T= able 1), presumably due to washing out the natamycin (which is insoluble in wa= ter) from the surface of cheeses by the brine. In spite of the low concentrati= on of natamycin, little mould development was observed after two weeks of ripening whereas mould development was observed considerably earlier on control cheeses. It should be mentioned that under the industrial conditi= ons, the concentration of natamycin capable of inhibiting mould development on= the surface of cheese may depend on the type of cheese and environmental conditions in the ripening room. The concentration of natamycin in the outermost 1 mm-thick outer layer of Jeziora½ski and Salami cheeses= after salting in natamycin-containing brine was 2.84 and 2.09 mg/dm² respe= ctively (Fig. 1), which exceeded the permissible concentration. During ripening, a rapid decline in the concentration of natamycin in cheese was observed. On the 28th day of ripening, before the cheeses were distributed, the concentration of natamycin in Salami cheese was 0.32 mg/dm², and in Jeziora½ski cheese was 0.79 mg/dm². Traces of natamycin were = also found in the second 1 mm layer of cheeses from the surface (1-2 mm) (Fig. 1). Throughout ripening, moulds did not grow on the surface of the experiment= al cheeses. In Jeziora½ski cheese, that was immerse aqueous suspensio= n of "Natamycin 50% In Lactose" after brining, the natamycin content= was higher than that in Salami cheeses that had been treated similarly (Fig. = 2). However, only in case of cheese that had been immersed for 60 sec in a 0.= 4% suspension of "Natamycin 50% In Lactose", did the natamycin lev= el exceeded the permissible concentration during the initial period of ripen= ing. During ripening, inactivation of natamycin was observed and was more intensive in Salami cheese. In the second layer from the outside of the cheese, the natamycin content was insignificant and by the 18th day of ripening had decreased to non-detectable levels. The higher concentration= of natamycin on the surface of Jeziora½ski cheese can be explained by= the fact that it srind is more porous (non-pressed cheese) than that in Salami che= ese (pressed cheese). During the ripening of Jeziora½ski and Salami ch= eeses, the development of ould on their surface was not observed. Other authors (Gri= pon and Bergere, 1972; Engel et al., 1983) also showed that the concentration= of natamycin in the outer layer of cheese and the depth of its migration depended on the type of cheese and on the duration of immersion in the suspension of "Natamycin 50% In Lactose". A major influence of the rind on= the concentration of natamycin = in cheeses, as well as on the depths of its migration, was confirmed (Table = 2). On the 4th day of ripening in the ch= eeses from which the rind had been removed, the concentration of natamycin in t= he outermost layer of cheeses was by 2.5 times higher than t hat in cheeses = with the rind. In rindless cheeses, the migration of natamycin to a depth of 5= mm was observed. The result of the study showed that natamycin protects the surface of cheese against the development of mould. For the efficient protection of the surface of alami and Jeziora½ski cheeses it is recommended to salt them in brine co= ntaining 0.2% "Natamycin 50% In Lactose" or to mmerse them for 30 sec in= a 0.4% aqueous suspension of "Natamycin 50% In Lactose". The suspension of "elvocid" in water or brine may be used for a long period. The concentration of natamycin in the outer layers of heese depen= ds on the type of cheese, rind performance and the method of application of "Natamycin 50% In Lactose". during ripening, natamycin adsorbed= in the outer layer of the cheeses is inactivated quickly. After four weeks of ipening, before the distribution of cheeses to retailers, natamycin was p= resent only, in the negligent quantities, in 1-mm thick outer layer of the chees= es. Immersing Gouda cheese for 30 sec in a 2% aqueous suspension of "Natamycin 50% In Lactose" before packing in Cryovac film, or soaking only of the bags in the above mentioned suspension effectively protected the surface of the cheese from the development of mould, even w= hen the coating was damaged. Natamycin present in "Natamycin 50% In Lactose" did not migrate into the Gouda cheese (Table 3). After the ripening period, requested by Polish quality standards, natamycin was not found in cheeses. growth, polyvinyl acetate (PVA) containing 0.05 % natam= ycin is usually applied. In Edam cheeses, coated with one, two, or three layers o= f PVA, the concentration of natamycin in the 1-mm outer layer of cheese was 0.43, 0.68 and 0.98 mg/dm² of cheese, respectively (Table 4). Natamycin wa= s not present in the second layer of cheese. In the cheeses coated with one or = two layers of PVA, natamycin was present for 15-18 days of ripening and when three layers of PVA were applied, it was present for 21-23 days. Early additional coating of cheeses with wax prolongated by a few days the pres= ence of natamycin in cheese. After from five to six weeks of ripening period cheeses did not contain natamycin. Polyvinyl acetate containing of 0.05% natamycin effectively protected the surface of cheeses against the development of undesirable moulds and simplified handling of cheese during the ripening period.
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