Screening of lactic acid bacteria and bifidobacteria for potential probiotic use in Iberian dry fermented sausages

The purpose of this study was to select lactic acid bacteria and bifibobacteria strains as potential probiotic cultures during the processing of Iberian dry fermented sausages. A total of 1000 strains were isolated from Iberian dry fermented sausages (363), and human (337) and pig faeces (300) in different culture media. Around 30% of these strains, mainly isolated from Iberian dry fermented sausages in LAMVAB agar, were pre-selected for testing as potential probiotics by their ability to grow adequately at the pH values and NaCl concentrations of these meat products during the ripening process. Of the in vitro investigations used to predict the survival of a strain in conditions present in the gastro intestinal tract, exposure to pH 2.5 showed itself to be a highly discriminating factor with only 51 out of 312 pre-selected strains resisting adequately after 1.5h of exposure. All acid-resistant isolates identified as lactobacilli originated from human faeces (Lactobacillus casei and Lactobacillus fermentum) and pig faeces (Lactobacillus reuteri, Lactobacillus animalis, Lactobacillus murinus, and Lactobacillus vaginalis). Pediococcus acidilactici strains were isolated from Iberian dry fermented sausages and pig faeces, whereas the greatest number of Enterococcus strains were identified as Enterococcus faecium, with this species being isolated from Iberian dry fermented sausages, and human and pig faeces. Most of these strains are promising probiotic meat culture candidates suitable for Iberian dry fermented sausages.     

发酵香肠风味物质气质分析及与发酵时间的关系

分析取样量、萃取时间、萃取温度3个因素对发酵香肠中挥发性成分萃取效果的影响,并对发酵6,9h的香肠中的香气成分进行了比较分析。结果表明:发酵香肠中风味物质的抽提条件为样品质量3.0g,萃取时间50min,萃取温度60℃。从发酵6,9h的香肠中分别鉴定出54,20种香气成分;酯类物质是发酵6h肠中主要挥发性成分,而发酵9h肠中主要成分为醇类,其中70.9%是乙醇,乙醇谱峰远高于其他化合物的谱峰,掩盖了其他化合物的谱峰。发酵6h与发酵9h的香肠中香气成分组成及相对含量具有明显的差异性。就风味物质而言,发酵6h的效果优于发酵9h的。     

Safety and functional aspects of pre‐selected pediococci for probiotic use in Iberian dry‐fermented sausages

The purpose of this study was to investigate pre‐selected pediococci for potential probiotic use in Iberian dry‐fermented sausages. A total of twelve strains isolated from Iberian dry‐fermented sausages and pig faeces were evaluated according to safety and functional characteristics including biogenic amines and d ‐lactic acid production, antibiotic susceptibility, cell adhesion and antimicrobial activity against food‐borne pathogens. The strain P. acidilactici SP979 was able to establish itself and compete with enteropathogens such as Salmonella choleraesuis on the intestinal epithelium and an inhibition of such pathogenic bacteria as Listeria monocytogenes and Staphylococcus aureus in vitro. This strain was also considered safe to be used with regard to its void aminogenic potential, low d ‐lactic acid production and antibiotic resistance pattern; being identified as a potential probiotic meat starter culture suitable for manufacture of dry‐fermented Iberian sausages.     

Influence of SFC, microstructure and polymorphism on texture (hardness) of binary blends of fats involved in the preparation of industrial shortenings

Several binary blends of vegetable oils commonly used in industrial shortenings (i.e., palm oil (PO), hydrogenated palm oil (HPO), soybean oil (SO), hydrogenated soybean oil (HSO), low-erucic acid rapeseed oil (LERO), hydrogenated low-erucic acid rapeseed oil (HLERO)) were studied for their physical properties such as solid fat content (SFC) by nuclear magnetic resonance (NMR) and textural properties (hardness). Microstructure was also observed by microscopy in order to explain the variability in hardness for samples having the same SFC values. The blends studied by microscopy were the following: HSO, HPO and HLERO diluted in LERO. For these three blends which had the same SFC, the level of network structure was different. HSO diluted in LERO had more crystals, closer to each other and overlapped. This can explain that HSO has a higher hardness than HPO or HLERO, for a same SFC value, when diluted in LERO. Polymorphism was also observed by powder X-ray diffraction. The variability in hardness for samples having the same SFC is due to various crystal types and/or network structures that are formed upon crystallization of hard fats. This work demonstrates that for binary blends of studied oils, changes in the hardness are controlled mostly by the SFC, polymorphism and also by the material’s microstructure.     

Computed tomography for quantitative determination of sodium chloride in ground pork and dry-cured hams

ABSTRACT:  Seventy-five ground meat and fat samples of pork with varying composition of sodium chloride (0% to 16%), fat (1% to 82%), protein (1% to 46%), and water (13% to 76%) were scanned by X-ray computed tomography (CT) at 110 kV. The dependency of CT value on chemical composition and the linear relationships between sodium chloride (NaCl) and CT value were modeled. When all ground samples were used for modeling and no information of chemical composition was included in the model, the prediction error for NaCl was 2.8%. Adding information on fat or protein content to the model reduced the error to 1.6%. A minimal prediction error of 0.2% for NaCl was found when the variation in chemical composition was strongly reduced. In addition, 22 samples of dry-cured ham lean and fat tissues at different processing stages were CT scanned; their chemical compositions were 0% to 14% NaCl, 1% to 85% fat, 5% to 33% protein, and 7% to 76% water. The NaCl content in dry-cured ham samples was modeled with prediction errors of 0.6% to 2.1%, depending on which chemical component was included in the models. In general, predictions were improved if either the range of concentrations was reduced or information of chemical composition was included in the models. Important sources of error in the models were the reproduction error for ground samples, and for ham samples the analytical errors in determining the chemical composition.