Fermentation of Texturized Pea Protein in Combination with Proteases for Aroma Development in Meat Analogues.

The potential use of texturized pea protein in meat analogues was investigated by comparing the effects of fermentation on pea and myofibrillar pork proteins in a model system including additives, microbial starters, and proteases. Model fermentation was controlled for 15 days by a pH decrease and microbial count and free amino acid increase. Besides, volatile production and sensory properties were evaluated at the end of fermentation. Protein type affected free amino acid generation and volatile profile. Models supplemented with proteases showed an increase in amino-acid-derived compounds (branched aldehydes and alcohols) and fruity odor notes. During fermentation, protease addition significantly reduced the production of linear aldehydes (pentanal, hexanal, and octanal) in vegetal models, while pyrazine compounds were not affected. This changes in the volatile profile reduced the legume beany odor but increased the perception of toasted cereal-like notes generated by the texturization process.

Short-Term Changes in Aroma-Related Volatiles in Meat Model: Effect of Fat and D. hansenii Inoculation.

This study assessed the effect of replacing pork lard with coconut oil and Debaryomyces hansenii inoculation on the biotransformation of amino acids into volatile compounds in a meat model system. Yeast counts, solid-phase microextraction, and gas chromatography/mass spectrometry were used to assess yeast growth and volatile production, respectively. Yeast growth was confirmed until 28 d, although the volatile profile changed until 39 d. Forty-three volatiles were quantified, and their odor activity values (OAVs) were calculated. The presence of fat and yeasts contributed to differences in volatiles. In pork lard models, a delayed formation of lipid-derived aldehyde compounds was observed, whereas in coconut oil models, the generation of acid compounds and their respective esters was enhanced. Yeast activity affected amino acid degradation, which produced an increase in branched-chain aldehydes and alcohols. The aroma profile in the coconut models was influenced by hexanal, acid compounds, and their respective esters, whereas in pork lard models, aroma was affected by methional (musty, potato) and 3-methylbutanal (green, cocoa). The yeast inoculation contributed to the generation of 3-methylbutanoic acid (cheesy) and phenylethyl alcohol (floral). The type of fat and yeast inoculation produced a differential effect on the aroma.

Influence of soaking and solvent extraction for deodorization of texturized pea protein isolate on the formulation and properties of hybrid meat patties.

BACKGROUND: Hybrid batters constitute the base for the processing of cooked and dry meat analogues. The use of texturized plant proteins in their formulation is a key strategy to reduce the consumption of animal proteins, although off-flavors present in these plant proteins often cause sensory rejection. The aim was to study the effect of a deodorization process of pea protein, for their use in hybrid meat batters at different percentages of substitution. RESULTS: Hybrid patties with higher percentages of pea protein showed higher values of yellowness, pH, and water activity, whereas hardness was reduced. Soaking treatment with ethanol for deodorization of the texturized pea protein increased humidity and pH in all patties but reduced the textural properties (hardness, springiness, cohesiveness, and chewiness). The addition of oat flour improved the patty texture at higher percentages of pea protein, but in soaked deodorized patty formulations it affected volatile retention. Volatile compounds related to off-flavors (aldehydes, alcohols, acid compounds, ketones, and pyrazines) appeared significantly increased as the pea percentage increased, although these were efficiently removed by the soaking deodorizing process applied. CONCLUSION: Soaking of the texturized pea protein with ethanol is an effective strategy to reduce off-flavors in hybrid meat patties. However, it produces changes in the textural characteristics by the solubilization of the proteins of the texturized pea, reducing the availability to form a network and affecting volatile retention. The formulation of hybrid batter should be controlled in all sensory aspects for the processing of cooked and dry cured meat product analogues. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Understanding the impact of nitrogen and sulfur precursors on the aroma of dry fermented sausages.

The goal of this study was to confirm and acquire more information about the nitrogen and sulfur compounds existing in the volatile profile of dry fermented sausages from the addition of precursors (proline, ornithine and thiamine), and their role in sausage aroma. To this end, the precursors were added to the formulation of sausages, which were submitted to a fermentation and drying process. The sausage aroma was analyzed by olfactometry technique and Free Choice Profile sensory analysis. The results showed that the addition of precursors impacted the aroma, and reduced the level of oxidation in the final sausages while microbial differences were mainly observed in Orn-sausages. Among the aroma compounds detected only 2-methyl-3-(methylthio)furan verified the effect of thiamine supplementation and the impact on the cured and savoury odours detected in Thia-sausages by Free Choice profile sensory analysis, while no clear effect could be attributed to specific volatile compounds in the nitrogen supplemented sausages.

Selection of Debaryomyces hansenii isolates as starters in meat products based on phenotypic virulence factors, tolerance to abiotic stress conditions and aroma generation.

INTRODUCTION: Debaryomyces hansenii is a yeast widely used in meat fermentations as starter for the purpose of improving the aromatic quality of the final product. However, it has not been the subject of an extensive study regarding phenotypic characteristics important for starter selection, such as the capacity to grow at abiotic stress conditions occurring during fermentation, the ability to generate desirable aromas and the absence of virulence traits in yeasts. AIMS: The aim of this study was to screen 60 strains of D. hansenii isolated from assorted foods for their potential application as starters in dry-cured fermented sausages manufacture. METHODS: The abiotic stress factors tested were low aw and pH and high concentration of salt, acetic acid and lactic acid. The phenotypic virulence traits explored were growth at 37°C, pseudohyphal and biofilm generation, invasiveness and enzymatic activities present in virulent yeasts. The generation of desirable meat aromas was tested in models containing aroma precursors applying an olfactory analysis. A quantitative profiling of stress tolerance was used to test the potential performance of selected strains in meat fermentations. RESULTS: The results demonstrated that most strains displayed no virulence trait or were only positive for biofilm production. Moreover, the strains showed large heterogeneity regarding their tolerance to abiotic stress factors, although most of them could grow at intermediate to high levels of the traits. The sensory analysis was the criteria determining the selection of starter strains. CONCLUSIONS: The evaluation of the phenotypic traits demonstrates that D. hansenii is a safe yeast, it is able to tolerate the stress in meat fermentation and it is able to generate desirable aromas. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study confirm the adequacy of selected D. hansenii strains to be applied as starters in meat products.

Aroma enhancement in dry cured loins by the addition of nitrogen and sulfur precursors.

Dry cured loins containing nitrogen (proline and ornithine) and sulfur (thiamine) compounds as precursors of aroma compounds at two concentration levels were manufactured. The effect of precursor addition on the microbiology and chemical parameters of loins was studied together with the aroma study performed by olfactometry and Free Choice Profile sensory analyses. Addition of precursors did not affect the microbial and chemical parameters, while aroma was affected when precursors were added at the highest level. The dry loin aroma profile was mainly composed by compounds 3-methylbutanal, methional, ethyl 3-methylbutanoate, 3-methylbutanoic acid, 1-octen-3-ol, 2-acetyl-1-pyrroline and 2-acetylpyrrole that contribute to musty, cooked potatoes, fruity, cheesy, mushroom, roasted and meaty odor notes. Proline and ornithine supplementation modified the loins aroma profile producing toasted odors, while the effect of thiamine supplementation on the aroma was revealed by the presence of sulfur derived compounds (methional and 2-methyl-3-(methylthio)furan) that contribute to the "cured meat odor".

Microbiota and volatilome of dry-cured pork loins manufactured with paprika and reduced concentration of nitrite and nitrate.

Dry-cured pork loin is a very popular meat product in Mediterranean countries. Pork-loin is manufactured rubbing curing salts, nitrite and nitrate, and spices on the surface of the loin which is then dry-cured or smoked for several months. Although nitrite-derived compounds are crucial for the microbiological safety and development of a distinct flavour, there have been recent concerns about the adverse health effects of nitrite-derived compounds driving to the reduction of curing agents in meat products. In this study, we have evaluated the differences in microbiota and aroma of dry-cured pork loins manufactured with or without paprika and reduced ingoing amounts of nitrate and nitrite. Staphylococcus dominated the microbiota of pork loins without paprika, regardless of the nitrite and nitrate reduction. On the contrary, the reduction of nitrite and nitrate in loins with paprika had an important effect on the microbiota. In these loins a codominance of Staphylococcus and Bacillus together by Enterobacteriaceae occurred. Moreover, paprika addition and reduction of nitrite and nitrate seemed to promote proliferation of lactic acid bacteria. Occurrence of these genera was correlated with the generation of free amino acids and their derived volatile compounds setting clear differences in the aroma profile of dry-cured loins.

Meaty aroma notes from free amino acids and thiamine in nitrite-reduced, dry-fermented, yeast-inoculated sausages.

The contribution of free amino acids and thiamine to the production of potent meat aroma compounds in nitrite-reduced, dry-fermented sausages inoculated with a D. hansenii strain was the objective of this study. For this, three different sausage formulations were manufactured; a control and two formulations reduced by half in nitrate and nitrite and one of them inoculated with D. hansenii. Free amino acids, thiamine content and savoury volatile compounds were analysed. Eleven savoury volatile compounds were quantitated. Among them, the most potent compounds above their odour thresholds were 2-methyl-3-furanthiol, 2-acetyl-1-pyrroline, methional, dimethyl trisulfide and methyl-2-methyl-3-furyl disulfide. Their generation was affected by D. hansenii inoculation as shown by the decrease in methional and methyl 2-methyl-3-furyl disulfide content, and the increase of methionol. Nitrate and nitrite reduction did not significantly affect amino acid and thiamine contents.

Nitrite reduction in fermented meat products and its impact on aroma.

Fermented meat products are important not only for their sensory characteristics, nutrient content and cultural heritage, but also for their stability and convenience. The aroma of fermented meat products is unique and its formation mechanisms are not completely understood; however, the presence of nitrite and nitrate is essential for the development of cured aroma. The use of nitrite and nitrate as curing agents in meat products is based on its preservation activity. Even though their presence has been associated with several risks due to the formation of nitrosamines, their use is guarantee due to their antimicrobial action against Clostridium botulinum. Recent trends and recommendations by international associations are directed to use nitrite but at the minimum concentration necessary to provide the antimicrobial activity against Clostridium botulinum. This chapter discuss the actual limits of nitrite and nitrite content and their role as curing agents in meat products with special impact on dry fermented products. Regulatory considerations, antimicrobial mechanisms and actual trends regarding nitrite reduction and its effect on sensory and aroma properties are also considered.

The Maillard Reaction as Source of Meat Flavor Compounds in Dry Cured Meat Model Systems under Mild Temperature Conditions.

Flavor is amongst the major personal satisfaction indicators for meat products. The aroma of dry cured meat products is generated under specific conditions such as long ripening periods and mild temperatures. In these conditions, the contribution of Maillard reactions to the generation of the dry cured flavor is unknown. The main purpose of this study was to examine mild curing conditions such as temperature, pH and aw for the generation of volatile compounds responsible for the cured meat aroma in model systems simulating dry fermented sausages. The different conditions were tested in model systems resembling dry fermented sausages at different stages of production. Three conditions of model system, labeled initial (I), 1st drying (1D) and 2nd drying (2D) and containing different concentrations of amino acid and curing additives, as well as different pH and aw values, were incubated at different temperatures. Changes in the profile of the volatile compounds were investigated by solid phase microextraction and gas chromatography mass spectrometry (SPME-GS-MS) as well as the amino acid content. Seventeen volatile compounds were identified and quantified in the model systems. A significant production of branched chain volatile compounds, sulfur, furans, pyrazines and heterocyclic volatile compounds were detected in the model systems. At the drying stages, temperature was the main factor affecting volatile production, followed by amino acid concentration and aw. This research demonstrates that at the mild curing conditions used to produce dry cured meat product volatile compounds are generated via the Maillard reaction from free amino acids. Moreover, in these conditions aw plays an important role promoting formation of flavor compounds.

Contribution of autochthonous yeasts with probiotic potential to the aroma profile of fermented Guajillo pepper sauce.

BACKGROUND: Three yeast strains with probiotic potential, Hanseniaspora opuntiae, Pichia kudriavzevii, and Wickerhamomyces anomalus were inoculated in the fermentation of Guajillo chilli pepper (Capsicum annuum L.) sauce, and the different aroma profiles were investigated. Using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis and gas chromatography-olfactometry (GCO), flavour compound production was evaluated during the fermentation of the Guajillo chilli pepper sauces. RESULTS: A total of 78 volatile compounds were identified during the yeast fermentation of the sauce. Most aldehydes and terpenes detected were present at the beginning of the fermentation, indicating a Guajillo chilli pepper origin. Among the 34 active aroma compounds detected by GCO, propanoic acid (cheesy), 3-methylbutanoic acid (sharp, cheese), ethyl 2-methylbutanoate (fruity), and 6-methyl-5-hepten-2-one (strong, citrus) were identified as key aroma contributors produced by the inoculation of the yeasts. A different aroma profile was produced by probiotic yeast. Hanseniaspora opuntiae produced an aroma profile with herbal and green notes based on high production of aldehydes, ketones, and acetic acid. Pichia kudriavzevii and W. anomalus produced fruity, green-herbal, and cheesy notes based on ester compounds, alcohol and branched-chain acids production although, the production of propanoic acid by W. anomalus increased the cheesy character in the sauces. CONCLUSION: The aroma profile of fermented chilli pepper sauces depends not only on the chili pepper varieties used but also on the fermentation process as a source of aroma compounds. The use of probiotic yeast can be used to improve and diversify the aroma profile of fermented chilli pepper sauces. © 2020 Society of Chemical Industry.

Counteracting the effect of reducing nitrate/nitrite levels on dry fermented sausage aroma by Debaryomyces hansenii inoculation.

The reduction of ingoing amounts of nitrate and nitrite in dry fermented sausages was studied together with the impact of Debaryomyces hansenii inoculation on aroma generation. Three different formulations of sausages were manufactured: control (C), reduced in nitrate and nitrite ingoing amounts (R) and reduced R inoculated with D. hansenii (RY). Changes in physicochemical and microbiological parameters, volatile compounds and aroma were investigated at different drying times. Nitrite/nitrate reduction did not seem to affect microbial growth but affected their metabolic activity. Moreover, nitrite/nitrate reduction decreased lipid oxidation and generation of derived volatile compounds. Yeast inoculation limited lipid oxidation and prevented nitrite oxidation. Sausage aroma profile was positively affected by D. hansenii inoculation which contributed to the generation of potent aroma compounds like ethyl ester compounds and 3-methylbutanal. Long drying time impacted sausage aroma profile as well as yeast metabolism. Yeast inoculation counteracted the negative influence of nitrite/nitrate reduction due to its antioxidant capacity, aroma generation and hindered nitrite oxidation.

Wickerhamiella verensis f.a. sp. nov., a novel yeast species isolated from subsoil groundwater contaminated with hydrocarbons and from a human infection.

Yeast strains belonging to a novel anamorphic yeast species were isolated from subsoil groundwater contaminated with hydrocarbons in a metal working factory located in northern Spain, and from a human infection in the USA. Comparison of ITS sequences between the isolates revealed 0.2 % divergence between the Spanish isolates and 0.46 % divergence between those and the USA isolate. Phylogenetic analysis based on the D1/D2 domains of the LSU rRNA gene showed that these isolates belong to the Wickerhamiella clade with W. sorbophila and W. infanticola as their closest relatives. Sequence divergence between the new isolates and W. sorbophila and W. infanticola was 1.97 and 1.79 %, respectively. The isolates in the novel species are not fermentative and pseudohyphae were not produced. Sexual reproduction was not observed for individual isolates or in mixtures of isolates. Conjugation between the isolates in the novel species and close relatives W. sorbophila and W. infanticola was not observed. These data support the proposal of Wickerhamiella verensis as a novel species, with CECT 12028T as the holotype.

Debaryomyces hansenii Metabolism of Sulfur Amino Acids As Precursors of Volatile Sulfur Compounds of Interest in Meat Products.

The ability of Debaryomyces hansenii to produce volatile sulfur compounds from sulfur amino acids and the metabolic pathway involved have been studied in seven strains from different food origins. Our results proved that l-methionine is the main precursor for sulfur compound generation. Crucial differences in the sulfur compound profile and amino acid consumption among D. hansenii strains isolated from different food sources were observed. Strains isolated from dry pork sausages displayed the most complex sulfur compound profiles. Sulfur compound production, such as that of methional, could result from chemical reactions or yeast metabolism, while according to this study, thioester methyl thioacetate appeared to be generated by yeast metabolism. No relationship between sulfur compounds production by D. hansenii strains and the expression of genes involved in sulfur amino acid metabolism was found, except for the ATF2 gene in the L1 strain for production of methyl thioacetate. Our results suggest a complex scenario during sulfur compound production by D. hansenii.

Microbial changes and aroma profile of nitrate reduced dry sausages during vacuum storage.

Slow fermented sausages with reduced ingoing amounts of sodium nitrate (control, 15% and 25% reduction) were stored under vacuum up to three months. Changes in microbiology, chemical parameters and volatile compounds were studied. Residual nitrate was not affected by vacuum storage and its reduction resulted in a reduction of sausage redness. General microbial counts decreased during vacuum storage, though nitrate reduction increased the growth of total mesophilic bacteria and Gram positive cocci. Long storage time and 25% nitrate reduction affected microbial activity and sausage aroma profile. Short vacuum storage times and moderate nitrate reduction (15%) were related to compounds producing pleasant odours (3-hydroxy-2-butanone, ethyl octanoate, ethyl-3-methylbutanoate and 2,3-pentanedione) and cheesy/buttery odour (2,3-butanedione and ethyl-2-hydroxypropanoate). In contrast, 25% nitrate reduction increased compounds like heptanal (green, unpleasant odour) and those related to unpleasant odours, methanethiol (rotten odour) and methional (cooked potato).

Nitrate reduction in the fermentation process of salt reduced dry sausages: Impact on microbial and physicochemical parameters and aroma profile.

Slow fermented sausages with reduced ingoing amounts of sodium nitrate were manufactured: control (250 ppm), 15% (212.5 ppm) and 25% (187.5 ppm) reduction. The effect of nitrate reduction on microbiology and chemical parameters, volatile compounds and aroma production was studied. Parameters like, pH, aw and colour decreased during ripening, without being affected by nitrate reduction. Lipid oxidation increased during ripening and it was higher in control sausages due to fat content. Residual nitrite was below the detection limit during the whole process and residual nitrate decreased during ripening, with higher reduction in RN25 sausages. Lactic acid bacteria, total mesophilic bacteria and yeasts and moulds increased during ripening but Gram positive cocci decreased. Microbial counts from nitrate reduced sausages at the end of the manufacturing process were not statistically different from the control sausages with nitrate. Regarding volatile compounds formation, compounds derived from amino acid degradation were increased by nitrate reduction. Aroma compounds derived from amino acid degradation and responsible for strong odours, dimethyl disulphide (toasted, garlic) and methional (cooked potato) and, to a lesser extent, compounds derived from esterase activity producing fruity odours (ethyl acetate, ethyl butanoate, ethyl­2­hydroxypropanoate, ethyl­2­methylbutanoate and ethyl­3­methylbutanoate) and several compounds from carbohydrate fermentation acetic acid (vinegar odour) and 2-butanone (fruity) were related to the high nitrate reduction (25%). Despite nitrate reduction up to 25% produced minor effect on microbial growth, their metabolism is regulated by nitrate content and therefore by nitrite generation affecting the production of key aroma compounds that alter the sausage aroma profile.

Lipolysis and aroma generation as mechanisms involved in masking boar taint in sodium reduced fermented sausages inoculated with Debaryomyces hansenii yeast.

BACKGROUND: The use of boar back fat for processing of fermented sausages may cause the presence of abnormal odours. In dry-cured products, ripening time is essential to develop the sensory characteristics. Yeast has been proposed as an alternative to mask boar taint odour through its metabolic activity but it is necessary to elucidate which mechanisms are involved. The aim is to study the effect of Debaryomyces hansenii inoculation on the lipolysis process and generation of aroma compounds in fermented sausages manufactured with boar back fat at two different ripening times. RESULTS: D. hansenii inoculated sausages had a higher degree of lipolysis as demonstrated by higher content of free fatty acids, ester compounds and branched aldehydes which contribute the fruity odour. The increase in lipolysis produced by D. hansenii inoculation was not followed by an increase in oxidation during processing possibly due to the metabolic activity of yeast. The effect of back fat type was scarcely appreciated whereas ripening time had a stronger effect on sausage. Boar sausages were characterised by a lower polyunsaturated fatty acid profile and lesser lipolysis than gilt sausages. CONCLUSION: Yeast inoculation with D. hansenii and long ripening time were appropriate strategies to limit the perception of boar taint in dry fermented sausages. © 2017 Society of Chemical Industry.