What are the drivers of beef sensory quality using metadata of intramuscular connective tissue, fatty acids and muscle fiber characteristics?

peer-reviewedThe aim of this integrative study was to investigate the relationships between biochemical traits (total, insoluble and soluble collagens (TCol, ICol, SCol), cross-links (CLs), proteoglycans (TPGs), proportion of fiber types, total lipids (TLips), main fatty acids (FAs) families, the n-6/n-3 polyunsaturated FA (n-6/n-3PUFA) ratio and the sensory attributes scores (tenderness, juiciness, flavor) of two muscles from beef: Rectus abdominis (RA) and Longissimus thoracis (LT). For robust analysis, a database was prepared using samples from three studies from animals raised under different production systems. The analyses were performed either on each study separately or on pooled data per muscle after removing as many experimental effects as possible in each study. The CLs (across the muscles and studies) and, to a lower extent, type IIA muscle fibers (mainly for RA muscles), saturated FAs (SFAs), monounsaturated FAs (MUFAs) (for the LT muscles) were the components the most frequently associated with tenderness. The CLs, type IIA muscle fibers (mainly for the RA muscles), TLips, SFAs, MUFAs, conjugated linoleic acids (CLAs) and n-6/n-3 PUFA ratio (mainly for the LT muscles) were the components the most associated with juiciness. The TLips and CLAs (across the muscles and studies), SFAs, MUFAs (mainly for the LT muscles), CLs (mainly for the RA muscles) and TPGs (mainly for the LT muscles) were the components the most associated with flavor liking. The CLs, CLAs, TLips, SFAs, MUFAs, n-6/n-3 PUFA ratio, type IIA and I muscle fibers were the components the most frequently associated with the 3 sensory scores taken together. The SCol, TPGs and type IIX+B muscle fibers were little associated with the sensory scores taken together. The TCol, ICol and PUFAs were components the least associated with sensory scores. The data of this integrative study highlighted for the first time that the CLs were negatively involved in the determination of the three sensory traits mainly in the RA muscle. The muscle fibers in this integrative study had a weak impact on the variations in beef sensory traits. The type IIA and IIX+B muscle fibers were respectively negatively and positively associated with tenderness, negatively associated with juiciness and flavor. The type I muscle fibers were overall positively associated with juiciness and flavor and negatively or positively with tenderness and these associations were muscle and study-dependent. Overall, the TLips and FAs were positively associated with the sensory scores and the n-6/n-3 PUFA ratio was negatively associated with them.European Commissio

Are there consistent relationships between major connective tissue components, intramuscular fat content and muscle fibre types in cattle muscle?

peer-reviewedIntramuscular connective tissue (IMCT) is mainly composed of several fibrils (known as total collagen (TCol)) linked between each other by different chemical cross-links (CLs), the whole being embedded in a matrix of proteoglycans (PGs). In the field of beef quality, there is limited information on the role of CLs and PGs. Accordingly, several authors suggest that, to investigate the role of IMCT, it is important to investigate them just like TCol and insoluble collagen (ICol). In muscle, there are two other components, the muscle fibres and intramuscular fat (IMF) content. There are limited data on the relationships between these three components of muscle and then on possibility to independently manipulate these characteristics in order to control the final quality of meat. The present study aimed to investigate whether consistent relationships exist between these different components of muscle. Therefore, the present study compared four muscles of two cattle types (dairy and beef) to determine associations between TCol, ICol, CLs and PGs. Data were analysed across and within muscle (M) and animal type (AT) based on residuals. There was a strong M and AT effect for all muscle characteristics and an interaction M × AT for type I muscle fibres and IMF. Correlations between TCol, ICol and their CLs were M- and AT-independent. Total proteoglycans were positively correlated with TCol and ICol in a muscle-dependent manner irrespective of AT, but no correlation was found with CLs. On the contrary, CLs were negatively correlated with the ratio TPGs : TCol in an M-dependent manner, irrespective of AT. TCol, ICol and CLs were positively and negatively correlated with type IIA and IIB+X muscle fibres only in longissimus thoracis (LT) muscle, regardless the AT. Insoluble collagen was the only parameter of IMCT to be correlated with type I muscle fibres but only in LT muscle, irrespective of AT. There was no correlation between PGs and muscle fibre types, but PGs were the only IMCT component to be related with IMF in an M-dependent manner, irrespective of AT. Finally, there was no correlation between muscle fibre types and IMF content within M and AT. This study revealed that there is a strong relationship between IMCT components irrespective of M, an M-dependent relationship between the IMCT components and muscle fibre types and few (only with PGs) or no relationship between IMF and IMCT and muscle fibres

Le massif du Koniambo, Nouvelle-Calédonie (Formation et obduction d'un complexe ophiolithique du type SSZ)

NOUMEA-BU (987352102) / SudocPOLYNESIE-BU (987352101) / SudocSudocFranceF

Imbrication complexe de croûte océanique/manteau supra-subductif et manteau lithosphérique dans un modèle de subduction - obduction : exemple du massif ophiolitique du Koniambo, Nouvelle Calédonie.

International audienc

Kinetics of the persistence of chromosomal DNA from genetically engineered Escherichia coli introduced into soil

International audienceInvestigations to quantify bacterial survival and DNA persistence of a genetically engineered population of Escherichia coli introduced into soil microcosms were carried out. The survival of E. coli was monitored by plate counting and immunofluorescence methods, whereas the persistence of the DNA was evaluated by using a most-probable-number-polymerase chain reaction method. Whereas the E. coli population density declined below the plate-counting-technique detection threshold (10(2) CFU.g-1) after 15 days, 10(3) extracellular and 5 x 10(5) total DNA target sequences were still detected after 40 days. Additionally, the E. coli cell counts fell below the detection limit of the immunofluorescence method (10(5) cells.g-1) before the end of the experiment. Colony hybridizations did not reveal gene transfer to the indigenous microflora. These results confirm the persistence of residual E. coli target sequences that could not be detected by the classical cell counting method and offer promising applications for the environmental detection of microorganisms, either engineered, pathogenic, or released for beneficial effects