From Waste to Taste-Efficient Production of the Butter Aroma Compound Acetoin from Low-Value Dairy Side Streams Using a Natural (Nonengineered) Lactococcus lactis Dairy Isolate

The Probiotic Enterococcus Lactis SF68 as a Potential Food Fermentation Microorganism for Safe Food Production

Due to the reports describing virulent and multidrug resistant enterococci, their use has become a topic of controversy despite most of them being safe and commonly used in traditionally fermented foods worldwide. We have characterized Enterococcus lactis SF68, a probiotic strain approved by the European Food Safety Authority (EFSA) for use in food and feed, and find that it has a remarkable potential in food fermentations. Genome analysis revealed the potential of SF68 to metabolize a multitude of carbohydrates, including lactose and sucrose, which was substantiated experimentally. Bacteriocin biosynthesis clusters were identified and SF68 was found to display a strong inhibitory effect against Listeria monocytogenes. Fermentation-wise, E. lactis SF68 was remarkably like Lactococcus lactis and displayed a clear mixed-acid shift on slowly fermented sugars. SF68 could produce the butter aroma compounds, acetoin and diacetyl, the production of which was enhanced under aerated conditions in a strain deficient in lactate dehydrogenase activity. Overall, E. lactis SF68 was found to be versatile, with a broad carbohydrate utilization capacity, a capacity for producing bacteriocins, and an ability to grow at elevated temperatures. This is key to eliminating pathogenic and spoilage microorganisms that are frequently associated with fermented foods.

Development and Evaluation of a Fermented Pistachio-Based Beverage Obtained by Colloidal Mill

The aim of the present study was to develop a fermented pistachio beverage as a plant-based alternative to milk-based drinks. For this purpose, a colloidal mill was used to finely grind and homogenize the pistachios to obtain a homogeneous consistency and prevent sedimentation. In addition, lactic acid bacteria fermentation was used to develop unique flavours and characteristics in the final product and to achieve microbiological stability for up to 30 days of storage a 4 °C. The formulated beverages were evaluated for chemical-physical characteristics (pH, organic acid production, and fructose, sucrose, and glucose content), nutritional profile (proximate composition, amino acid and GABA content), and volatile organic composition by HS-SPME-GC/MS analysis. The pistachio-based beverages were characterized by a good source of protein, fat, fiber, and minerals (mainly K and P). The colloidal mill contributed to creating a homogeneous texture and to making the nutrients readily available to the starter microorganisms, which reached concentrations above 108 ufc/mL in the final products. The beverages were characterized by pronounced acidity and some by the presence of acetoin and 2,3-butanedione, volatile components associated with a yogurt- or kefir-like aroma. This innovative approach provides an alternative to traditional milk-based beverages and highlights the role of LAB in the development of nutritious and attractive plant-based beverages.

The role of fermentation with lactic acid bacteria in quality and health effects of plant-based dairy analogues

The modern food industry is undergoing a rapid change with the trend of production of plant-based food products that are more sustainable and have less impact on nature. Plant-based dairy analogues have been increasingly popular due to their suitability for individuals with milk protein allergy or lactose intolerance and those preferring a plant-based diet. Nevertheless, plant-based products still have insufficient nutritional quality, undesirable structure, and earthy, green, and bean-like flavor compared to dairy products. In addition, most plant-based foods contain lesser amounts of essential nutrients, antinutrients limiting the bioavailability of some nutrients, and allergenic proteins. Novel processing technologies can be applied to have a homogeneous and stable structure. On the other hand, fermentation of plant-based matrix with lactic acid bacteria can provide a solution to most of these problems. Additional nutrients can be produced and antinutrients can be degraded by bacterial metabolism, thereby increasing nutritional value. Allergenic proteins can be hydrolyzed reducing their immunoreactivity. In addition, fermentation has been found to reduce undesired flavors and to enhance various bioactivities of plant foods. However, the main challenge in the production of fermented plant-based dairy analogues is to mimic familiar dairy-like flavors by producing the major flavor compounds other than organic acids, yielding a flavor profile similar to those of fermented dairy products. Further studies are required for the improvement of the flavor of fermented plant-based dairy analogues through the selection of special microbial cultures and formulations.

Thiamine-Starved Lactococcus lactis for Producing Food-Grade Pyruvate

Lactococcus lactis is a safe lactic acid bacterium widely used in dairy fermentations. Normally, its main fermentation product is lactic acid; however, L. lactis can be persuaded into producing other compounds, e.g., through genetic engineering. Here, we have explored the possibility of rewiring the metabolism of L. lactis into producing pyruvate without using genetic tools. Depriving the thiamine-auxotrophic and lactate dehydrogenase-deficient L. lactis strain RD1M5 of thiamine efficiently shut down two enzymes at the pyruvate branch, the thiamine pyrophosphate (TPP) dependent pyruvate dehydrogenase (PDHc) and α-acetolactate synthase (ALS). After eliminating the remaining enzyme acting on pyruvate, the highly oxygen-sensitive pyruvate formate lyase (PFL), by simple aeration, the outcome was pyruvate production. Pyruvate could be generated by nongrowing cells and cells growing in a substrate low in thiamine, e.g., Florisil-treated milk. Pyruvate is a precursor for the butter aroma compound diacetyl. Using an α-acetolactate decarboxylase deficient L. lactis strain, pyruvate could be converted to α-acetolactate and diacetyl. Summing up, by starving L. lactis for thiamine, secretion of pyruvate could be attained. The food-grade pyruvate produced has many applications, e.g., as an antioxidant or be used to make butter aroma.

Utilization of plant derived lactic acid bacteria for efficient bioconversion of brewers' spent grain into acetoin

Brewers' spent grain (BSG) is a major side-stream from the beer industry, with an annual estimated production of 39 million tons worldwide. Due to its high nutritional value, high abundance and low price, it has been proposed as an ingredient in human food. Here we investigated the ability of different lactic acid bacteria to produce the flavor molecule acetoin in liquid BSG extract, in order to broaden the possibilities of utilization of BSG in human food. All the investigated lactic acid bacteria (LAB) covering the Leuconostoc, Lactobacillus and Lactoccocus species were able to convert the fermentable sugars in liquid BSG into acetoin. Production levels varied significantly between the different LAB species, with Leuconostoc pseudomesenteroides species reaching the highest titers of acetoin with only acetate as the main byproduct, while also being the fastest consumer of the fermentable sugars present in liquid BSG. Surprisingly, the currently best investigated LAB for acetoin production, L. lactis, was unable to consume the maltose fraction of liquid BSG and was therefore deemed unfit for full conversion of the sugars in BSG into acetoin. The production of acetoin in Leu. pseudomesenteroides was pH dependent as previously observed in other LAB, and the conversion of BSG into acetoin was scalable from shake flasks to 1 L bioreactors. While all investigated LAB species produced acetoin under aerobic conditions, Leu. pseudomesenteroides was found to be an efficient and scalable organism for bioconversion of liquid BSG into a safe acetoin rich food additive.

Superior anodic electro-fermentation by enhancing capacity for extracellular electron transfer

Anodic electro-fermentation (AEF), where an anode replaces the terminal electron acceptor, shows great promise. Recently a Lactococcus lactis strain blocked in NAD+ regeneration was demonstrated to use ferricyanide as an alternative electron acceptor to support fast growth, but the need for high concentrations of this non-regenerated electron acceptor limits practical applications. To address this, growth of this L. lactis strain, and an adaptively evolved (ALE) mutant with enhanced ferricyanide respiration capacity were investigated using an anode as electron acceptor in a bioelectrochemical system (BES) setup. Both strains grew well, however, the ALE mutant significantly faster. The ALE mutant almost exclusively generated 2,3-butanediol, whereas its parent strain mainly produced acetoin. The ALE mutant interacted efficiently with the anode, achieving a record high current density of 0.81 ± 0.05 mA/cm2. It is surprising that a Lactic Acid Bacterium, with fermentative metabolism, interacts so well with an anode, which demonstrates the potential of AEF.

Transforming acid whey into a resource by selective removal of lactic acid and galactose using optimized food-grade microorganisms

The presence of lactic acid and galactose makes spray drying of acid whey (AW) a significant challenge for the dairy industry. In this study, a novel approach is explored to remove these compounds, utilizing food-grade microorganisms. For removing lactic acid, Corynebacterium glutamicum was selected, which has an inherent ability to metabolize lactic acid but does so slowly. To accelerate lactic acid metabolism, a mutant strain G6006 was isolated through adaptive laboratory evolution, which metabolized all lactic acid from AW two times faster than its parent strain. To eliminate galactose, a lactose-negative mutant of Lactococcus lactis that cannot produce lactate was generated. This strain was then co-cultured with G6006 to maximize the removal of both lactic acid and galactose. The microbially "filtered" AW could readily be spray dried into a stable lactose powder. This study highlights the potential of utilizing food-grade microorganisms to process AW, which currently constitutes a global challenge.

Efficient production of acetoin from lactate by engineered Escherichia coli whole-cell biocatalyst

Acetoin, an important and high-value added bio-based platform chemical, has been widely applied in fields of foods, cosmetics, chemical synthesis, and agriculture. Lactate is a significant intermediate short-chain carboxylate in the anaerobic breakdown of carbohydrates that comprise ~ 18% and ~ 70% in municipal wastewaters and some food processing wastewaters, respectively. In this work, a series of engineered Escherichia coli strains were constructed for efficient production of acetoin from cheaper and abundant lactate through heterogenous co-expression of fusion protein (α-acetolactate synthetase and α-acetolactate decarboxylase), lactate dehydrogenase and NADH oxidase, and blocking acetate synthesis pathways. After optimization of whole-cell bioconversion conditions, the engineered strain BL-11 produced 251.97 mM (22.20 g/L) acetoin with a yield of 0.434 mol/mol in shake flasks. Moreover, a titer of 648.97mM (57.18 g/L) acetoin was obtained in 30 h with a yield of 0.484 mol/mol lactic acid in a 1-L bioreactor. To the best of our knowledge, this is the first report on the production of acetoin from renewable lactate through whole-cell bioconversion with both high titer and yield, which demonstrates the economy and efficiency of acetoin production from lactate. Key Points • The lactate dehydrogenases from different organisms were expressed, purified, and assayed. • It is the first time that acetoin was produced from lactate by whole-cell biocatalysis. • The highest titer of 57.18 g/L acetoin was obtained with high theoretical yield in a 1-L bioreactor.

Improving acetoin production through construction of a genome-scale metabolic model

Acetoin was widely used in food, medicine, and other industries, because of its unique fragrance. Bacillus amyloliquefaciens was recognized as a safe strain and a promising acetoin producer in fermentation. However, due to the complexity of its metabolic network, it had not been fully utilized. Therefore, a genome-scale metabolic network model (iJYQ746) of B. amyloliquefaciens was constructed in this study, containing 746 genes, 1736 reactions, and 1611 metabolites. The results showed that Mg²⁺, Mn²⁺, and Fe²⁺ have inhibitory effects on acetoin. When the stirring speed was 400 rpm, the maximum titer was 49.8 g L^-1. Minimization of metabolic adjustments (MOMA) was used to identify potential metabolic modification targets 2-oxoglutarate aminotransferase (serC, EC 2.6.1.52) and glucose-6-phosphate isomerase (pgi, EC 5.3.1.9). These targets could effectively accumulate acetoin by increasing pyruvate content, and the acetoin synthesis rate was increased by 610% and 10%, respectively. This provides a theoretical basis for metabolic engineering to reasonably transform B. amyloliquefaciens and produce acetoin.

Utilization of delactosed whey permeate for the synthesis of ethyl acetate with Kluyveromyces marxianus

Ethyl acetate is an important organic solvent and currently produced from fossil carbon resources. Microbial synthesis of this ester from sugar-rich waste could be an interesting alternative. Therefore, synthesis of ethyl acetate by Kluyveromyces marxinanus DSM 5422 from delactosed whey permeate (DWP) was studied in an aerated stirred bioreactor at 40 °C. DWP is mainly composed of residual lactose and minerals. The minerals inhibited yeast growth, as witnessed by an increased lag period, a reduced growth rate, and an extended process duration. All experiments were therefore carried out with diluted DWP. In a series of batch experiments, the pH of iron-deficient DWP medium varied between 4.8 and 5.9. The pH of the cultivation medium significantly influenced cell growth and product syntheses, with the highest ethyl acetate yield of 0.347 g g^-1 and lowest by-product formation achieved at pH 5.1. It is likely that this effect is due to pH-dependent iron chelation, which affects the iron bioavailability and the intracellular iron content, thus affecting growth and metabolite synthesis. The viability of yeast cells was always high despite the harsh conditions in DWP medium, which enabled extended usage of the biomass in repeated-batch and fed-batch cultivations. These two culture techniques increased the volume of DWP processed per time by 32 and 84% for the repeated-batch and the fed-batch cultivation, respectively, without a drop of the ester yield. KEY POINTS: • Delactosed whey permeate was converted to ethyl acetate with a high rate and yield. • The formation of ethyl acetate in DWP medium at iron limitation is pH-dependent. • Highly active yeasts from batch processes enabled extension as fed and repeated batch.

Immunomodulatory action of Lactococcuslactis

Fermented foods are gaining popularity due to health-promoting properties with high levels of nutrients, phytochemicals, bioactive compounds, and probiotic microorganisms. Due to its unique fermentation process, Lactococcus lactis plays a key role in the food business, notably in the manufacturing of dairy products. The superior biological activities of L. lactis in these functional foods include anti-inflammatory and immunomodulatory capabilities. L. lactis boosted growth performance, controlled amino acid profiles, intestinal immunology, and microbiota. Besides that, the administration of L. lactis increased the rate of infection clearance. Innate and acquired immune responses would be upregulated in both local and systemic compartments, resulting in these consequences. L. lactis is often employed in the food sector and is currently being exploited as a delivery vehicle for biological research. These bacteria are being eyed as potential candidates for biotechnological applications. With this in mind, we reviewed the immunomodulatory effects of different L. lactis strains.

Fermented butter aroma for plant-based applications

Plant-based dairy alternatives are gaining increasing interest, e.g. alternatives to yoghurt, cheese, and butter. In all these products butter flavor (diacetyl + acetoin) plays an important role. We previously have reported efficient butter flavor formation from low value dairy side streams using a dairy isolate of Lactococcus lactis deficient in lactate dehydrogenase. Here, we have tested the ability of this strain, RD1M5, to form butter flavor in plant milks based on oat and soy. We found that oat milk, with its high sugar content, supported more efficient production of butter aroma, when compared to soy milk. When supplemented with glucose, efficient butter aroma production was achieved in soy milk as well. We also carried out an extended adaptive laboratory evolution of the dairy strain in oat milk. After two months of adaptation, we obtained a strain with enhanced capacity for producing butter aroma. Despite of its high sugar content, RD1M5 and its adapted version only metabolized approximately 10% of the fermentable sugars available in the oat milk, which we found was due to amino acid starvation and partly starvation for vitamins. The study demonstrates that dairy cultures have great potential for use in plant-based fermentations.

Consolidated Bioprocessing in a Dairy Setting─Concurrent Yoghurt Fermentation and Lactose Hydrolysis without Using Lactase Enzymes

Streptococcus thermophilus is a fast-growing lactic acid bacterium (LAB) used in yoghurt and cheese manufacturing. Recently, we reported how this bacterium could serve as a cell catalyst for hydrolyzing lactose when permeabilized by nisin A. To enhance the lactose hydrolyzing activity of S. thermophilus, we mutated a dairy strain and screened for variants with elevated β-galactosidase activity. Two isolates, ST30-8 and ST95, had 2.4-fold higher activity. Surprisingly, both strains were able to hydrolyze lactose when used as whole-cell lactase catalysts without permeabilization, and ST30-8 hydrolyzed 30 g/L lactose in 6 h at 50 °C using 0.18 g/L cells. Moreover, both strains hydrolyzed lactose while growing in milk. Genome sequencing revealed a mutation in l-lactate dehydrogenase, which we believe hampers growth and increases the capacity of S. thermophilus to hydrolyze lactose. Our findings will allow production of sweet lactose-reduced yoghurt without the use of costly purified lactase enzymes.

Isolation and Identification of Lactococcus lactis and Weissella cibaria Strains from Fermented Beetroot and an Investigation of Their Properties as Potential Starter Cultures and Probiotics

The presence of certain microorganisms in dairy products or silage is highly desirable. Among them are probiotic strains of lactic acid bacteria (LAB), which show many beneficial features, including antimicrobial properties that support the development of beneficial microflora; in addition, owing to their biochemical activity, they influence the nutritional, dietary, and organoleptic properties of food products. Before being placed on the market, each strain requires separate testing to determine its probiotic properties and effectiveness. The aim of this study was to isolate LAB strains from a pickled beetroot sample that could be used in the dairy industry and with the potential to be considered as a probiotic in the future. Two strains identified using the MALDI technique were selected—Lactococcus lactis and Weissella cibaria. The optimal growth conditions of the strains were determined, and their proteolytic properties were assessed with the use of the o-PA reagent and spectrophotometry. The lipid profile was analyzed using the SALDI (surface-assisted laser desorption/ionization) technique and silver nanoparticles. High-performance liquid chromatography was used to assess the ability of the strains to synthesize beneficial metabolites, such as B vitamins (B2, B3, and B9) or lactic acid, and gas chromatography was used to analyze the substances responsible for organoleptic properties. Moreover, the ability to inhibit the growth of pathogenic strains was also tested in the selected strains. Both tested strains demonstrated the desired properties of starter cultures for future use in functional food production, showing that fermented plant products can serve as valuable potential probiotic sources.

Harnessing cross-resistance - Sustainable nisin production from low-value food side streams using a Lactococcus lactis mutant with higher nisin-resistance obtained after prolonged chlorhexidine exposure

Nisin has a tendency to associate with the cell wall of the producing strain, which inhibits growth and lowers the ceiling for nisin production. With the premise that resistance to the cationic chlorhexidine could reduce nisin binding, variants with higher tolerance to this compound were isolated. One of the resistant isolates, AT0606, had doubled its resistance to nisin, and produced three times more free nisin, when cultured in shake flasks. Characterization revealed that AT0606 had an overall less negatively charged and thicker cell wall, and these changes appeared to be linked to a defect high-affinity phosphate uptake system, and a mutation inactivating the oleate hydratase. Subsequently, the potential of using AT0606 for cost efficient production of nisin was explored, and it was possible to attain a high titer of 13181 IU/mL using a fermentation substrate based on molasses and a by-product from whey protein hydrolysate production.

Advances in biological production of acetoin: a comprehensive overview

Acetoin, a high-value-added bio-based platform chemical, is widely used in foods, cosmetics, agriculture, and the chemical industry. It is an important precursor for the synthesis of: 2,3-butanediol, liquid hydrocarbon fuels and heterocyclic compounds. Since the fossil resources are becoming increasingly scarce, biological production of acetoin has received increasing attention as an alternative to chemical synthesis. Although there are excellent reviews on the: application, catabolism and fermentative production of acetoin, little attention has been paid to acetoin production via: electrode-assisted fermentation, whole-cell biocatalysis, and in vitro/cell-free biocatalysis. In this review, acetoin biosynthesis pathways and relevant key enzymes are firstly reviewed. In addition, various strategies for biological acetoin production are summarized including: cell-free biocatalysis, whole-cell biocatalysis, microbial fermentation, and electrode-assisted fermentation. The advantages and disadvantages of the different approaches are discussed and weighed, illustrating the increasing progress toward economical, green and efficient production of acetoin. Additionally, recent advances in acetoin extraction and recovery in downstream processing are also briefly reviewed. Moreover, the current issues and future prospects of diverse strategies for biological acetoin production are discussed, with the hope of realizing the promises of industrial acetoin biomanufacturing in the near future.

Food grade microbial synthesis of the butter aroma compound butanedione using engineered and non-engineered Lactococcus lactis

The design-build-test-learn (DBTL) cycle has been implemented in metabolic engineering processes for optimizing the production of valuable compounds, including food ingredients. However, the use of recombinant microorganisms for producing food ingredients is associated with different challenges, e.g., in the EU, a content of more than 0.9% of such ingredients requires to be labeled. Therefore, we propose to expand the DBTL cycle and use the "learn" module to guide the development of non-engineered strains for clean label production. Here, we demonstrate how this approach can be used to generate engineered and natural cell factories able to produce the valuable food flavor compound - butanedione (diacetyl). Through comprehensive rerouting of the metabolism of Lactococcus lactis MG1363 and re-installment of the capacity to metabolize lactose and dairy protein, we managed to achieve a high titer of diacetyl (6.7 g/L) in pure dairy waste. Based on learnings from the engineering efforts, we successfully achieved the production of diacetyl without using recombinant DNA technology. We accomplish the latter by process optimization and by relying on high-throughput screening using a microfluidic system. Our results demonstrate the great potential that lies in combining metabolic engineering and natural approaches for achieving efficient production of food ingredients.

Fine-Tuning of Process Parameters Modulates Specific Metabolic Bacterial Activities and Aroma Compound Production in Semi-Hard Cheese

The formation of cheese flavor mainly results from the production of volatile compounds by microorganisms. We investigated how fine-tuning cheese-making process parameters changed the cheese volatilome in a semi-hard cheese inoculated with Lactococcus (L.) lactis, Lactiplantibacillus (L.) plantarum, and Propionibacterium (P.) freudenreichii. A standard (Std) cheese was compared with three variants of technological itineraries: a shorter salting time (7 h vs 10 h, Salt7h), a shorter stirring time (15 min vs 30 min, Stir15min), or a higher ripening temperature (16 °C vs 13 °C, Rip16°C). Bacterial counts were similar in the four cheese types, except for a 1.4 log₁₀ reduction of L. lactis counts in Rip16°C cheeses after 7 weeks of ripening. Compared to Std, Stir15min and Rip16°C increased propionibacterial activity, causing higher concentrations of acetic, succinic, and propanoic acids and lower levels of lactic acid. Rip16°C accelerated secondary proteolysis and volatile production. We thus demonstrated that fine-tuning process parameters could modulate the cheese volatilome by influencing specific bacterial metabolisms.

Purified lactases versus whole-cell lactases-the winner takes it all

Lactose-free dairy products are in great demand worldwide due to the high prevalence of lactose intolerance. To make lactose-free dairy products, commercially available β-galactosidase enzymes, also termed lactases, are used to break down lactose to its constituent monosaccharides, glucose and galactose. In this mini-review, the characteristics of lactase enzymes, their origin, and ways of use are discussed in light of their potential for hydrolyzing lactose. We also discuss whole-cell lactase catalysts, which appear to have great potential in terms of cost reduction and convenience, and which are more natural alternatives to purified enzymes. Lactic acid bacteria (LAB) already used in food fermentations seem to be optimal candidates for whole-cell lactases. However, they have not been industrially exploited yet due to technical hurdles. For whole-cell lactases to be efficient, the lactase enzymes inside the cells must be made available for lactose hydrolysis, and thus, cells need to be permeabilized or disrupted prior to use. Here we review state-of-the-art approaches for disrupting or permeabilizing microorganisms. Lastly, based on recent scientific achievements, we propose a novel, resource-efficient, and low-cost scenario for achieving lactose hydrolysis at a dairy plant using a LAB whole-cell lactase.Key points• Lactases (β-galactosidase) are essential for producing lactose-free dairy products• Novel permeabilization techniques facilitate the use of LAB lactases• Whole-cell lactase catalysts have great potential for reducing costs and resources Graphical abstract.

Efficient Production of Nisin A from Low-Value Dairy Side Streams Using a Nonengineered Dairy Lactococcus lactis Strain with Low Lactate Dehydrogenase Activity

Nisin is commonly used as a biopreservative in foods. For industrial production, nisin-producing Lactococcus lactis strains are usually grown to high cell densities to achieve the highest possible nisin titer. However, accumulation of lactic acid eventually halts production, even in pH-controlled fermentations. Here, we describe a nisin-producing L. lactis strain Ge001, which was obtained after transferring the nisin gene cluster from L. lactis ATCC 11454, by conjugation, into the natural mutant L. lactis RD1M5, with low lactate dehydrogenase activity. The ability of Ge001 to produce nisin was tested using dairy waste as the fermentation substrate. To accommodate redox cofactor regeneration, respiration conditions were used, and to alleviate oxidative stress and to reduce adsorption of nisin onto the producing cells, we found it to be beneficial to add 1 mM Mn²⁺ and 100 mM Ca²⁺, respectively. A high titer of 12 084 IU/mL nisin could be reached, which is comparable to the highest titers reported using expensive, rich media. Summing up, we here present a 100% natural, robust, and sustainable approach for producing food-grade nisin and acetoin from readily available dairy waste.

O’Sullivan M, Kerry JP, Kilcawley KN. A Cross-Cultural Evaluation of Liking and Perception of Salted Butter Produced from Different Feed Systems

Perception and liking among Irish, German and USA consumers of salted butter produced from different feed systems-outdoor grass (FS-GRSS), grass/clover (FS-CLVR), and indoor concentrate (FS-TMR)-was investigated. A consumer study was conducted in all three countries. Irish and German assessors participated in ranking descriptive analysis (RDA), whereas descriptive analysis (DA) was carried out by a trained panel in the USA. Volatile analysis was conducted to identify differences in aroma compounds related to cow diet. Overall, there was no significant difference in overall liking of the butters, among USA, German and Irish consumers, although cross-cultural preferences were evident. Sensory attribute differences based on cow diet were evident across the three countries, as identified by German and Irish assessors and trained USA panelists, which are likely influenced by familiarity. The abundance of specific volatile aromatic compounds, especially some aldehydes and ketones, were significantly impacted by the feed system and may also contribute to some of the perceived sensory attribute differences in these butters.