Lipolytic and microbial changes during the natural fermentation and ripening of Greek dry sausages

The potentials and challenges of using fermentation to improve the sensory quality of plant-based meat analogs

Despite the advancements made in improving the quality of plant-based meat substitutes, more work needs to be done to match the texture, appearance, and flavor of real meat. This review aims to cover the sensory quality constraints of plant-based meat analogs and provides fermentation as a sustainable approach to push these boundaries. Plant-based meat analogs have been observed to have weak and soft textural quality, poor mouth feel, an unstable color, and unpleasant and beany flavors in some cases, necessitating the search for efficient novel technologies. A wide range of microorganisms, including bacteria such as Lactobacillus acidophilus and Lactiplantibacillus plantarum, as well as fungi like Fusarium venenatum and Neurospora intermedia, have improved the product texture to mimic fibrous meat structures. Additionally, the chewiness and hardness of the resulting meat analogs have been further improved through the use of Bacillus subtilis. However, excessive fermentation may result in a decrease in the final product's firmness and produce a slimy texture. Similarly, several microbial metabolites can mimic the color and flavor of meat, with some concerns. It appears that fermentation is a promising approach to modulating the sensory profiles of plant-derived meat ingredients without adverse consequences. In addition, the technology of starter cultures can be optimized and introduced as a new strategy to enhance the organoleptic properties of plant-based meat while still meeting the needs of an expanding and sustainable economy.

Effect of partial replacement of pork meat with an olive oil organogel on the physicochemical and sensory quality of dry-ripened venison sausages

A venison salchichon was made using varying proportions of olive oil to replace the traditional pork meat and to obtain a healthier product. Six types of salchichon were produced. The control type contained 75% lean venison and 25% pork meat; in the other types, 15%, 25%, 35%, 45% and 55% of the pork meat were replaced by olive oil introduced in the form of an organogel (olive oil emulsified with soy protein and water). All types were satisfactory in terms of physicochemical characteristics (pH, a(w), moisture loss) and instrumental colour throughout ripening, and displayed acceptable levels of lipolysis (acidity index) and lipid oxidation (TBARS). Higher proportions of olive oil prompted an increase in monounsaturated fatty acid content (mainly C18:1). All six types of salchichon were judged acceptable by consumers, the highest scores being given to those in which no more than 25% of the pork meat was replaced by olive oil.

Lipolytic Changes in Fermented Sausages Produced with Turkey Meat: Effects of Starter Culture and Heat Treatment

In this study, the effects of two different commercial starter culture mixes and processing methodologies (traditional and heat process) on the lipolytic changes of fermented sausages manufactured with turkey meat were evaluated during processing stages and storage. Free fatty acid (FFA) value increased with fermentation and during storage over 120 d in all fermented sausage groups produced with both processing methodologies (p<0.05). After drying stage, free fatty acid values of traditional style and heat processed fermented sausages were between 10.54-13.01% and 6.56-8.49%, respectively. Thiobarbituric acid (TBA) values of traditionally processed fermented sausages were between 0.220-0.450 mg·kg(-1), and TBA values of heat processed fermented sausages were in a range of 0.405-0.795 mg·kg(-1). Oleic and linoleic acids were predominant fatty acids in all fermented sausages. It was seen that fermented sausage groups produced with starter culture had lower TBA and FFA values in comparison with the control groups, and heat application inhibited the lipase enzyme activity and had an improving effect on lipid oxidation. As a result of these effects, heat processed fermented sausages had lower FFA and higher TBA values than the traditionally processed groups.

The influence of Debaryomyces hansenii and Candida utilis on the aroma formation in garlic spiced fermented sausages and model minces

The influence of the yeast starter cultures Debaryomyces hansenii and Candida utilis on fermented meat aroma was studied in model minces and in commercial-type fermented sausages. Volatile compounds from model minces and sausages were collected using diffusive and dynamic headspace sampling respectively and were identified by gas chromatography/mass spectrometry (GC/MS). A triangle test was carried out on the sausages to detect whether the yeast influenced the sausage odour. C. utilis demonstrated high metabolic activity in the model minces, producing several volatile compounds, in particularly esters. C. utilis also seemed to ferment the amino acids valine, isoleucine and leucine into compounds important for the aroma of sausages. D. hansenii on the contrary, had very little effect on the production of volatile compounds in the model minces. In the sausage experiment both yeast cultures died out before the ripening process ended and the sensory analysis showed only a slight difference between the sausages. A fungistatic test of the garlic powder added to the sausages indicated that garlic inhibits the growth of the yeast starter cultures.

Improving functional value of meat products

In recent years, much attention has been paid to develop meat and meat products with physiological functions to promote health conditions and prevent the risk of diseases. This review focuses on strategies to improve the functional value of meat and meat products. Value improvement can be realized by adding functional compounds including conjugated linoneleic acid, vitamin E, n3 fatty acids and selenium in animal diets to improve animal production, carcass composition and fresh meat quality. In addition, functional ingredients such as vegetable proteins, dietary fibers, herbs and spices, and lactic acid bacteria can be directly incorporated into meat products during processing to improve their functional value for consumers. Functional compounds, especially peptides, can also be generated from meat and meat products during processing such as fermentation, curing and aging, and enzymatic hydrolysis. This review further discusses the current status, consumer acceptance, and market for functional foods from the global viewpoints. Future prospects for functional meat and meat products are also discussed.

Preliminary analysis of the lipase gene (gehM) expression of Staphylococcus xylosus in vitro and during fermentation of naturally fermented sausages (in situ

Coagulase-negative catalase-positive cocci (CNCPC) play a very important role during the fermentation of sausages. In particular, they are involved in the aroma formation of the final product, because they release lipases that are able to free short-chain fatty acids that are contributing to the sensory characteristics of the fermented sausage. Few studies have been undertaken to elucidate the regulation of lipase gene expression in Staphylococcus xylosus by substrate molecules or products of lipolysis. The aim of this study was to analyze the gehM gene expression of S. xylosus DSMZ 6179 in vitro with growth media containing different concentrations of lipids and in situ during the maturation of fermented sausages. The results obtained suggest that a concentration that increases in triglycerides in the growth medium suppresses the expression of the lipase gene.

New developments in the study of the microbiota of naturally fermented sausages as determined by molecular methods: A review

The microflora of different types of fermented sausages has been defined by isolation and biochemical identification of the microorganisms commonly found in these products. It is generally agreed that the main microbial groups involved in such products are lactic acid bacteria and coagulase-negative cocci. In addition, and depending on the product, other groups may play a role, such as yeasts and enterococci. Since it appears that the types of microbial groups, or even the specific strains of a given microbial group, that dominate the fermentation, significantly affect the organoleptic profile of the final product, there is an increasing interest in the description of the microbiota that are found in different fermented sausages. More recently, new tools, based on molecular methods, allowing fast and unequivocal identification of strains, isolated from fermented sausages, became available. These methods have been successfully applied and, in general, biochemical and molecular identification compared well. However, new information comes to light when molecular methods are applied to DNA and/or RNA extracted directly from sausages. This approach eliminates problems related to traditional isolation. This review deals with the recent findings and results of the application of molecular methods, in a culture-dependent and culture-independent manner, on the study of the microflora of fermented sausages.

Identification of yeast strains isolated from a two-phase decanter system olive oil waste and investigation of their ability for its fermentation

A dynamic fed-batch microcosm system is described which permits assessment of the progressive growth of yeasts through olive oil waste. We report on its application to measure the effects of the growth of yeast strains upon the chemical composition of "alpeorujo", the waste of a two-phase decanter system used for the extraction of olive oil. Six phenotypically distinct groups of yeasts were isolated. Three selected isolates were identified as being most closely related to Saccharomyces sp., Candida boidinii and Geotrichum candidum using biochemical tests and partial 18S rDNA gene sequence analysis. This is the first report of yeast growth on "alpeorujo" by the use of a fed-batch microcosm system, resulting in the change of the initial chemical composition of "alpeorujo" and in the decrease of the toxic substances such as phenols.

A survey of yeasts in traditional sausages of southern Italy

The evolution of the yeast population during manufacturing and ripening of 'salsiccia sotto sugna', a typical salami of the Lucania region (southern Italy), was investigated. Four different batches, produced in four farms in Lucania, were studied. Each batch showed a specific yeast population, and the most frequently isolated yeasts belonged to Debaryomyces hansenii and its anamorph Candida famata, and Rhodotorula mucilaginosa. Yarrowia lipolytica was isolated from three sausage batches. The Y. lipolytica isolates were further characterised, in particular for their lipolytic activity on pork fat. Lipolytic activity was maximal at pH 5.5, with oleic and palmitic acids as major free fatty acids produced. The use of randomly amplified polymorphic DNA-polymerase chain reaction allowed the detection of a high genetic heterogeneity among the isolates phenotypically assigned to the species Y. lipolytica.

Contribution of the microbial and meat endogenous enzymes to the free amino acid and amine contents of dry fermented sausages

The role of the starter culture and meat endogenous enzymes on the free amino acid and amine contents of dry fermented sausages was studied. Five batches of sausages were prepared. The control batch was manufactured with aseptic ingredients without microbial inoculation. The other four experimental batches were manufactured with aseptic ingredients inoculated with Lactobacillus plantarum 4045 or Micrococcus-12 or L. plantarum 4045 and Micrococcus-12 or L. plantarum 4045 and Staphylococcus sp. Their effects on pH, a(w), myofibrillar proteins, and free amino acid and amine contents were studied. Sausages inoculated only with L. plantarum 4045 or with this starter combined with a Micrococcaceae had the lowest pH as a result of carbohydrate fermentation. In all batches similar patterns were observed for myofibrillar proteins and free amino acids which could indicate that meat endogenous proteases play an important role in proteolytic phenomena. No changes were observed in the amine fraction, indicating that the strains used as starter cultures did not show amino acid decarboxylase activity.

A novel modelling approach for predicting microbial growth in a raw cured meat product stored at 3 degrees C and at 12 degrees C in air

To predict microbial growth during chill storage of a traditional Greek raw sausage, a numerical model was developed and validated. In our novel approach, the specific growth rate of each microbial population was calculated on the basis of the main microbial populations grown in the sausage. In addition, the specific destructive effect of the sausage ecosystem was introduced to evaluate microbial growth. The model was integrated by the Runge-Kutta method and the parameter values were optimised by the least squares method. Fitting of the model to the experimental data derived from four sausage batches stored aerobically at 3 and 12 degrees C successfully described the microbial growth kinetics in the sausage niche. Finally, the parameter values estimated by the fitting of the model on the data set from each batch were used to predict microbial growth in the other batches at both storage temperatures.

Comparative study of lactic acid bacteria house flora isolated in different varieties of 'chorizo'

A total of 516 strains of lactic acid bacteria isolated from 'chorizo' (a Spanish dry fermented sausage) were identified. The 'chorizo' was from three zones of Castilla and León in Spain: Burgos, Segovia and Salamanca. Two factories were chosen in each zone and the samples were taken at three stages of ripening. L. sake was the most predominant species present (68.8%) followed by L. curvatus (16.47%) and Pediococcus sp. (8.52%). Different strains that do not belong to the above species were grouped as Lactobacillus sp. Group S1 comprising maltose and lactose negative L. sake was the main group present in all factories except in a factory in Segovia where group S3 comprising lactose positive L. sake and pediococci were the predominant ones. Group S1 increased during the ripening process in all six factories and it dominated in the ripened 'chorizo' except in the mentioned factory in Segovia. In general strains of L. sake and L. curvatus which fermented maltose but not lactose were more dominant at the beginning and in the middle of the process, whereas, L. sake and L. curvatus which could ferment lactose, or lactose and maltose occurred in higher numbers in semi-ripened 'chorizo' and in the final product. This indicates that strains which could ferment lactose were more competitive towards the end of the process. Strains from group S1 were the microorganisms responsible for the pH drop in most of the factories, giving the correct texture. As a result it would appear that a strain from this group would be most suitable for use as starter culture.

The combined effects of environmental conditions on lipolysis of pork fat by lipases of the meat starter culture organisms Staphylococcus xylosus and Debaryomyces hansenii

The effects of environmental conditions on lipolysis by cell-free extracts from the meat starter culture organisms Staphylococcus xylosus and Debaryomyces hansenii were studied using pork fat emulsions as model systems. For the individual effects of temperature and pH it was found that the optimal conditions for the lipolysis by S. xylosus lipase were 37 degrees C and pH 7.0, and 37 degrees C and pH 6.5 for the lipolysis by D. hansenii lipase. For the combined effects of conditions relevant to meat fermentation, i.e. 10-30 degrees C, pH 4.7-6.0, 2.5-7.5% (w/v) NaCl and incubation times of 2-6 days, the empirical models indicated that temperature, pH and incubation time had important effects on total lipolysis whereas NaCl concentration had little effect. For both cultures lipolysis was strongly inhibited at conditions of meat fermentation compared to optimal conditions. For any set of the conditions which were examined the total lipolysis caused by D. hansenii lipase was lower than that caused by S. xylosus lipase.

Characterisation of lactic acid bacteria isolated from naturally fermented Greek dry salami

A total of 348 lactic acid bacteria isolated from five batches of naturally fermented dry salami at various stages of ripening were characterised. The majority of the strains were assigned to two main phylogenetic groups of species: (i) the psychrotrophic, formerly called atypical, meat streptobacteria (169 strains) and (ii) a new genus Weissella (120), which was recently proposed (Collins et al., 1993) to include Leuconostoc paramesenteroides and some other closely related species. Meat streptobacteria were identified as Lactobacillus curvatus (88 strains) and L. sake (76), whereas 5 strains were indistinguishable and, thus designated L. sake/curvatus. Non-psychrotrophic streptobacteria were also isolated and identified as L. plantarum (34 strains), L. farciminis (10), L. coryniformis (1) and L. casei subsp. pseudoplantarum (1). The majority of the Weissella strains (86) were leuconostoc-like bacteria; four of them were identified as W. viridescens, 11 belonged to the newly described W. hellenica (Collins et al., 1993), another 11 resembled W. paramesenteroides, whereas 60 isolates were not classified to any species. The latter group comprised strains that produced D(L)-lactate. The remaining Weissella were gas-forming, arginine-positive rods assigned to W. minor (31) and W. halotolerans (3). Other species identified were Enterococcus faecium (10), Leuconostoc mesenteroides (1), L. brevis (1) and Pediococcus sp. (1). The main criteria used to distinguish between above species as well as their distribution on the five salami batches in relation to their succession with time and suitability as starters were discussed.