Influence of raw milk microflora on the characteristics of Swiss-type cheeses : II. Biochemical and sensory characteristics

Abstract

Using the same microfiltered milk, three 'raw milk' Swiss-type minicheeses were made after addition of three different retentates; one, remaining bacteria-free, was used as reference. The experiment was repeated three times at two different seasons. Factorial discriminant analyses were made on biochemical, physico-chemical and microbiological data at 12 weeks (end of warm storage, 18 "C) and 24 weeks (end of cold storage, 7 "C), At each ripening period, 'raw milk' cheeses were easily and significantly separated from the reference cheese. At 12 weeks, the three 'raw milk' cheeses were separated on the basis of propionic fermentation products, and to a lesser extent on proteolysis and levels of facultatively heterofermentative lactobacilli and starter lactic acid bacteria. At 24 weeks, differentiation was mainly based on proteolysis, since volatile fatty acids and lactate concentrations were nearly the same, irrespective of the cheeses. The same conclusions were drawn for win ter and autumn chee ses. Based on sensory evaluations made at the end of ripening, it was also possible to differentiate between the different 'raw milk' cheeses in winter and in autumn. Reference cheeses were always clearly separated from the other cheeses. The qualitative and quantitative importance of the indigenous microf1ora of milk on the biochemical and sensory characteristics of Swiss-type cheeses has been discussed. Swiss-type minicheese 1 microflora 1 proteolysis 1 volatile fatty acid 1 sensory analysis Rsum -Influence de la microflore du lait cru sur les caractristiques des fromages pte presse cuite: II. Caractristiques biochimiques et sensorielles. Des minifromages pte presse cuite ont t fabriqus partir de lait cru microfi!tr, auquel taient ajouts des rtentats provenant de trois origines diffrentes. Chacun des trois rtentats issus de la microfiltration tait rincorpor dans le lait microfiltr de mlange, pour obtenir trois fromages dits au lait cru. Le lait microfiltr ser-Oral communication at the IDF Symposium 'Ripening and Quality of Cheeses ', Besanon, France, February 26-28, 1996. y Demarigny el al vait de tmoin. L'exprimentation a t rpte trois fois, en automne et en hiver. Une analyse factorielle discriminante a t effectue, pour chaque saison, sur les donnes biochimiques, physico-chimiques et microbiologiques collectes 12 semaines (sortie cave chaude, 18 "C) et 24 semaines (sortie cave froide, 7 "C). chaque stade, les fromages au lait cru se diffrenciaient significativement du tmoin. De plus, 12 semaines, il tait dj possible de caractriser les trois fromages au lait cru, principalement partir de leur profil fermentaire, et dans une moindre mesure sur les niveaux de protolyse et de certaines populations microbiennes (lactobacilles htrofermentaires facultatifs, bactries lactiques du levain). 24 semaines, la diffrenciation portait essentiellement sur les niveaux de certains paramtres de protolyse, les concentrations en lactate, actate et propionate tant identiques quels que soient les fromages. Des analyses sensorielles, ralises sur les minifromages en fin d'affinage, ont permis de discriminer les trois origines des fromages au lait cru en hiver et en automne. Les fromages tmoins taient aussi clairement spars des autres fromages. L'importance qualitative et quantitative de la microflore originelle du lait sur les caractristiques biochimiques et sensorielles des fromages pte presse cuite, est discute. fromage pte presse cuite / microflore / protolyse / acide gras volatil / analyse sensorielle y Demarigny et al J~l~k_AJ t~iIl~~1. J~1i~k~l ,