Scanning Electron and Light Microscopic Study of Microbial Succession on Bethlehem St. Nectaire Cheese

Abstract

St. Nectaire cheese is a semisoft cheese of French origin that, along with Brie and Camembert cheeses, belongs to the class of surface mold-ripened cheese. The surface microorganisms that develop on the cheese rind during ripening impart a distinctive aroma and flavor to this class of cheese. We have documented the sequential appearance of microorganisms on the cheese rind and in the curd over a 60-day ripening period. Scanning electron microscopy was used to visualize the development of surface fungi and bacteria. Light microscopy of stained paraffin sections was used to study cross sections through the rind. We also monitored the development of bacterial and yeast populations in and the pH of the curd and rind. The earliest stage of ripening (0 to 2 days) is dominated by the lactic acid bacterium Streptococcus cremoris and multilateral budding yeasts, primarily Debaryomyces and Torulopsis species. Geotrichum candidum follows closely, and then zygomycetes of the genus Mucor develop at day 4 of ripening. At day 20, the deuteromycete Trichothecium roseum appears. From day 20 until the end of the ripening process, coryneforms of the genera Brevibacterium and Arthrobacter can be seen near the surface of the cheese rind among fungal hyphae and yeast cells.

Purification and characterization of two extracellular proteinases from Arthrobacter nicotianae 9458

“…Arthrobacter spp., together with B. linens, are the main microorganisms found on several bacterial smear and mould surface-ripened cheeses [6,9]. Several authors reported that growth of B. linens was essential for the development of the characteristic £avors, colors, aromas and textures of smear surface-ripened cheeses [6,16].…”

“…are Gram-positive chemo-organotrophs with a respiratory metabolism, never fermentative, widely distributed among the bacterial population of the soil. However, species of the genus Arthrobacter are major components of the smear mi-cro£ora of the surface-ripened cheeses [1,6^8] and also of mould surface-ripened cheeses, such as Brie and Camembert [9]. Despite their presence at high cell numbers on the surface of several cheeses, no studies on the enzymology of dairy Arthrobacter spp.…”

Purification and characterization of an extracellular proline iminopeptidase from Arthrobacter nicotianae 9458

“…and other acid-sensitive bacteria, such as Brevibacterium, Micrococcus and Corynebacterium spp., dominate the surface micro£ora of several bacterial surface smear-ripened cheeses such as Limburger, Mu « nster, Saint-Paulin, Appenzeller, Trappist, Tilsiter, Taleg-gio and Quartirolo [6^13]. Species of the genus Arthrobacter are major components also of mould surface-ripened cheeses, such as Brie and Camembert [13]. Low molecular mass compounds, produced through the combined action of various extracellular hydrolases produced by the smear micro£ora, di¡use into the interior of the cheese and are essential in determining the ¢nal characteristics and attributes of these cheeses.…”

The microstructure and distribution of micro-organisms within mature Serra cheese

“…© 1998 The Society for Applied Microbiology particularly in close-packed emulsion systems Parker et al 1995) such as full-fat cheese. As there have been no previous studies on the microstructure of Serra cheese, it is not known whether the diverse wild microflora is distributed evenly throughout the cheese matrix, or confined to specific regions as is known to occur in other cheeses, such as Cheddar (Dean et al 1959;Rammell 1960) and St Nectaire (Marcellino and Benson 1992). Nor is it clear why the final flavour characteristics of Serra are influenced by the degree of manual working of the curd (Macedo et al 1993), so that cheeses of differing flavours can be produced by a cheese-maker using the same batch of milk and the same ripening conditions.…”