Impact of broken cells of lactococci or propionibacteria on the ripening of Saint-Paulin UF-cheeses: extent of proteolysis and GC-MS profiles

Abstract

International audienceUF-cheeses have been successfully developed in many countries. However, proteolysis and the general extent of ripening were shown to be far slower compared to traditional varieties. The absence of starter lysis has been cited as a plausible explanation. In this work, propionibacteria and lactococci cells were disrupted using a new pilot homogenizer. Crude broken suspension (CBS), or cell-free extract (CFE), obtained after centrifugation, were added to UF-St Paulin retentate (concentration factor 6) made with a usual lactic starter. RO water was added to the control. Proteolysis was estimated by NCN, NPN and free amino acids. Neutral volatile compounds were determined by GC-MS. A low extent of ripening was noted in the control and the absence of starter lysis was effectively proved using immunodetection of lactococci cytoplasmic proteins. The addition of lactococci CBS or CFE increased free amino acid content (1.5 to 3 times) whereas propionibacteria CBS or CFE exhibited no significant increase, even when cheeses were ripened at 20 °C instead of 12 °C. By contrast, addition of propionibacteria CBS generated a significant increase in several volatile compounds like alcohols and ketones, whereas CFE did not, showing that the presence of live cells was required to form these compounds. CBS or CFE of lactococci did not significantly change the volatile compound profile. In conclusion, it was possible to influence the ripening of UF-cheese by the addition of crude broken bacterial cell suspensions. Other strains and species should now be investigated.Impact d'extraits cellulaires de lactocoques et de propionibactéries sur l'affinage de fromages UF : étendue de la protéolyse et profils CG-MS. Les fromages UF se sont développés avec succès dans de nombreux pays. Cependant, sans action technologique complémentaire, la protéolyse et par conséquent l'affinage sont nettement plus lents que dans les produits obtenus par les procédés traditionnels. L'absence de lyse du levain pourrait constituer une des causes possibles. Dans ce travail, des cellules de P. freudenreichii et de Lactococcus sp. ont été "cassées " à l'aide d'un nouvel homogénéisateur pilote. Les suspensions cassées brutes (CBS) ou les extraits intracellulaires (CFE) obtenus après centrifugation, ont été ajoutés à des rétentats UF de type St Paulin (concentration $\times$6) acidifiés à l'aide d'un levain lactique mésophile commercial. De l'eau osmosée était ajoutée au témoin. La protéolyse a été estimée par la mesure des teneurs en NCN, NPN et en acides aminés libres ; les composés volatils neutres par CG-MS. Dans le témoin, cette protéolyse était très limitée et l'absence de lyse du levain commercial (L. lactis) a été effectivement démontrée. L'addition de CBS ou de CFE de Lactococcus augmentait la teneur en acides aminés libres (1,5 à 3 fois). Cet accroissement n'était pas observé lors de l'addition de CBS ou de CFE de P. freudenreichii, même lorsque la température d'affinage était élevée à 20 °C au lieu de 12 °C. Par contre, l'addition de ...

Dynamic Analysis of the Lactococcus lactis Transcriptome in Cheeses Made from Milk Concentrated by Ultrafiltration Reveals Multiple Strategies of Adaptation to Stresses

“…Despite their commercial success, UF-cheeses have been reported repeatedly to be far slower in ripening than traditional cheeses (22). Several hypotheses have been proposed to explain this disadvantage, such as the high whey protein concentration or the large buffering capacity, which could delay the rate of autolysis (18,37). Even though several solutions to the question of what influences the rate of proteolysis in UFcheeses have been proposed, the genetic components controlling autolysis in this matrix have been poorly studied.…”

Influence of medium-concentration factor microfiltration treatment on the characteristics of low-moisture Mozzarella cheese

“…As κ-GMP does not belong to this fraction, the significant increase seen for MMC after 15 days of aging may indicate that the lysis of the starter culture cells which releases peptidases into the cheese juice was higher in this cheese. This hypothesis is related to the higher buffering capacity of MMC inhibiting autolysis of mesophilic lactic starters [32]. Nevertheless, no difference in this nitrogen fraction was observed at 60 days of ripening time, which indicated a similar level of proteolysis.…”

“…The release of proteases and peptidases into the cheese juice was slower as was the hydrolysis of the casein matrix. This low level of proteolysis could be an advantage for cheese varieties, such as Minas frescal [32] or Mozzarella, for which consumers expect a fresh lactic flavor and stability in the functionality during shelf life. For other varieties, adjustment of technological cheese-making parameters, such as the use of the thermophilic starters, partial pre-removal of calcium salts [29], or the addition of attenuated or broken starter cells [33], have to be performed to obtain similar proteolytic patterns.…”

“…The resulting MF permeate named "ideal whey" [5] because of its composition and its characteristics (sterile, native components with highly functional properties, and no fat) has a high added value potential market in comparison to classical whey as described by Maubois et al [22]. This economic advantage in addition to the technological benefits of the use of caseinenriched cheese milk explains the fast implementation of 0.1-μm MF technology in the European and the US cheese-making industries [28,32].…”

Preparation of serocolostrum by membrane microfiltration

“…Total solids, fat, proteins and lactose were determined by using reference analytical methods previously described by Saboya et al [33].…”