Non-protein Nitrogen Compounds Research Articles

Biochemical influence of <i>Annona muricata</i> on the basal renal profile of healthy adult Wistar rats

Numerous ethnopharmacological benefits have been attributed to Annona muricata, including, wound healing, anti-arthritic, hypolipidemic, anti-inflammatory, anti-nociceptive, anti-hypertensive, hepatoprotective and antineoplastic effects. This study is a baseline investigation of the influence of A. muricata on renal profile of healthy adult Wistar rats. A total of 144 adult male Wistar rats of average weight (100 - 150 g) were randomly divided into six groups (1-6): Group 1 served as control (0 mg/kg), Groups 2, 3, 4, 5 and 6 were orally treated doses of methanol extracts of the leaf, stem-bark, fruit-pulp or root-bark of A. muricata (each) at 100, 200, 400, 600 and 800 mg/kg body weight respectively, for a total of twenty-eight days consecutively. At the end of the experimental period, biochemical assays were done, including, plasma electrolytes and plasma urea/creatinine. The results of rats treated with different parts of A. muricata exhibited various changes. The changes observed in plasma electrolytes and non-protein nitrogen compounds did not give information of any significant deleterious effects for the rats treated with leaf and fruit-pulp extracts, as there were relative decreases in plasma urea and creatinine levels at the highest administered dose (800 mg/kg) following an initial increase (600 mg/kg). Conversely, the plasma urea and creatinine levels of rats treated with stem-bark and root-bark extracts significantly increased at 800 mg/kg, when compared with control. The fruit-pulp caused a significantly increased plasma urea/creatinine, while the root-bark extract led to a decrease, both at 800 mg/kg. The study indicates that A. Muricata possess relatively safe toxicity influence on renal functions.

Unprecedented 3D K-MOF to probe sensing of non-protein nitrogen (NPN) compounds and hazardous anions

The fluorescence of a unique potassium-based metal-organic framework [K(H3PMIDA)]n(1), PMIDA [N-(phosphonomethyl)iminodiacetic acid hydrate] has been prepared and used as a fluorescent sensor for sensitive and selective recognition of Non-Protein Nitrogen (NPN) compounds (creatinine, creatine, uric acid) and anions (Brˉ, Clˉ, CO32ˉ and Fˉ). During NPN detection, (1) displays fluorescence enhancement towards creatinine, and creatine. The detection limits for creatinine, creatine, uric acid and Brˉ, Clˉ, CO32ˉ, Fˉ ions are calculated to be 0.93, 0.45, 0.72 and 0.61, 0.72, 0.16, 0.03 ppm.

Metabolizam i iskorištenje neproteinskih dušićnih spojeva u preživača

Unique stomach physiology allows ruminants to utilise any form of dietary nitrogen (N) as a protein source. Ruminant N requirements can be divided into N requirements for microbial fermentation and host requirements for amino acids. Ruminant diets often contain non-protein nitrogen (NPN) compounds, a group of components that are not proteins but can be converted to proteins by rumen microbes. Therefore, NPN compounds in ruminant diets serve as alternative sources of ammoniacal nitrogen (NH3-N), which is necessary for the synthesis of microbial protein (MCP) in the rumen. MCP is an important component of metabolizable protein for ruminants and, under certain production conditions, may be the only amino acid source for synthesis of tissues and products. In this manner, ruminants utilise NPN compounds without having enzymes for their degradation. The use of NPN compounds in ruminant nutrition allows for an increase in feed consumption and utilisation, as well as the substitution of protein supplements, which in turn leads to more cost-effective production. However, abrupt supplementation or excessive consumption of NPN could negatively affect MCP synthesis, feed digestion, and animal production. On the other hand, it may lead to animal poisoning and the release of large amounts of N into the environment. Knowledge of N metabolism in the rumen, as well as optimization of its utilisation, sets the conditions for the presumed beneficial effects of NPN compounds in ruminant diets, without adverse effects on animal health and the environment. Therefore, the aim of this study was to summarize the recent literature data on the metabolism and utilisation of NPN compounds in ruminants.

Extraction of plant protein from green leaves: Biomass composition and processing considerations

There is an increasing need to explore alternative sources of proteins for food applications. Green leaves contain high levels of the enzyme RuBisCO, representing a source of protein with good functional and nutritional properties. However, the optimal conditions for extraction and purification of RuBisCO at a large scale have not yet been defined. This review discusses the main factors affecting the extraction of proteins from green leaves, from plant composition in terms of protein content and other compounds that affect the yield and quality of extractable protein, to the essential steps and challenges faced during extraction and purification, including considerations for achieving food-grade ingredient status. There are some key factors to consider when developing a protein concentrate for human consumption. The first step is the selection of an optimal raw material; plant tissues are complex matrices that require thorough characterization, including non-protein nitrogen and other undesirable compounds. The effect of the extraction and purification process on functionality, oxidation and proteolytic stability should also be considered. Moreover, the appropriate removal of undesired compounds must be considered to obtain plant protein concentrates suitable for food products. • Green leaves are an alternative source of proteins for human consumption. • Green leaves vary in their composition, which determines protein extractability. • Producing plant protein for food applications requires a scalable process. • Complete exploitation of plant biomass is key for a sustainable process. • New technologies such as aeroponics offer enhanced control over growing conditions.

Screening of non-protein nitrogen compounds in lactose refining streams from industrial whey permeate processing

The NPN compounds from dairy processing side-streams are a promising source for new products. In this study, the NPN profile of lactose production samples was screened using GC–MS and 1H NMR spectroscopy. These analytical platforms allowed the identification of 35 NPN compounds including, amino acids and derivatives, amino alcohols, organic acids, and other classes. Quantification of the NPN compounds revealed their attenuation by unit operations during a trial lactose production. Urea, ammonia, glycerophosphocholine, creatine, creatinine, orotic acid and choline were the most dominant compounds. Mother liquor concentrate had the highest concentration of NPN, whereas lactose powder had substantial relative amounts of N-acetylglucosamine, phosphocholine and orotic acid. The NPN compounds added up to 57–99% of the total nitrogen, depending on the sample type. The highest nitrogen recovery was found for the reverse osmosis retentate, mother liquid concentrate, wash water and reverse osmosis permeate, whereas the lowest was found for lactose powder.

Prediction of fresh and ripened cheese yield using detailed milk composition and udder health indicators from individual Brown Swiss cows.

The composition of raw milk is of major importance for dairy products, especially fat, protein, and casein (CN) contents, which are used worldwide in breeding programs for dairy species because of their role in human nutrition and in determining cheese yield (%CY). The aim of the study was to develop formulas based on detailed milk composition to disentangle the role of each milk component on %CY traits. To this end, 1,271 individual milk samples (1.5 L/cow) from Brown Swiss cows were processed according to a laboratory model cheese-making procedure. Fresh %CY (%CYCURD), total solids and water retained in the fresh cheese (%CYSOLIDS and %CYWATER), and 60-days ripened cheese (%CYRIPENED) were the reference traits and were used as response variables. Training-testing linear regression modeling was performed: 80% of observations were randomly assigned to the training set, 20% to the validation set, and the procedure was repeated 10 times. Four groups of predictive equations were identified, in which different combinations of predictors were tested separately to predict %CY traits: (i) basic composition, i.e., fat, protein, and CN, tested individually and in combination; (ii) udder health indicators (UHI), i.e., fat + protein or CN + lactose and/or somatic cell score (SCS); (iii) detailed protein profile, i.e., fat + protein fractions [CN fractions, whey proteins, and nonprotein nitrogen (NPN) compounds]; (iv) detailed protein profile + UHI, i.e., fat + protein fractions + NPN compounds and/or UHI. Aside from the positive effect of fat, protein, and total casein on %CY, our results allowed us to disentangle the role of each casein fraction and whey protein, confirming the central role of β-CN and κ-CN, but also showing α-lactalbumin (α-LA) to have a favorable effect, and β-lactoglobulin (β-LG) a negative effect. Replacing protein or casein with individual milk protein and NPN fractions in the statistical models appreciably increased the validation accuracy of the equations. The cheese industry would benefit from an improvement, through genetic selection, of traits related to cheese yield and this study offers new insights into the quantification of the influence of milk components in composite selection indices with the aim of directly enhancing cheese production.

Review of the Current Research on Fetal Bovine Serum and the Development of Cultured Meat.

The purpose of this review is to summarize studies that investigate blood and the main components of fetal bovine serum (FBS) in vertebrates, including major livestock, and review the current research on commercializing cultured meat. Detailed research on FBS is still lacking; however, some studies have shown that FBS consists of proteins, carbohydrates, growth factors, cytokines, fats, vitamins, minerals, hormones, non-protein nitrogen, and inorganic compounds. However, there are few studies on how the composition of FBS differs from blood or serum composition in adult animals, which is probably one of the main reasons for not successfully replacing FBS. Moreover, recent studies on the development of FBS replacers and serum-free media have shown that it is difficult to conclude whether FBS has been completely replaced or serum-free media have been developed successfully. Our review of the industrialization of cultured meat reveals that many basic studies on the development of cultured meat have been conducted, but it is assumed that the study to reduce or replace ingredients derived from fetuses such as FBS has not yet been actively developed. Therefore, developing inexpensive and edible media is necessary for the successful industrialization of cultured meat.

Changes in Protein and Non-Protein Nitrogen Compounds during Fishmeal Processing—Identification of Unoptimized Processing Steps

Quality changes of protein and non-protein nitrogen compounds during industrial fishmeal processing of fatty pelagic species (mackerel/herring rest material blend, MHB) and lean fish (whole blue whiting, BW) were studied to identify processing steps that require optimization to allow production of products for human consumption. Samples from protein-rich processing streams throughout the fishmeal production were analyzed for proximate composition, salt soluble protein content (SSP), biogenic amines (BA), total volatile basic nitrogen (TVB-N), trimethylamine (TMA), and dimethylamine (DMA). Mass flows throughout processing were balanced based on the total mass and proximate composition data. The quality of the final fishmeal products was highly dependent on the fish species being processed, indicating that the processes require optimization towards each raw material. The chemical composition changed in each processing step, resulting in different properties in each stream. Most of the non-protein nitrogen compounds (including BA, TVB-N, TMA, and DMA) followed the liquid streams. However, the concentrate contributed less than 20% to the produced fishmeal quantity. Mixing of this stream into the fishmeal processing again, as currently carried out, should thus be avoided. Furthermore, the cooking, separating, and drying steps should be optimized to improve the water and lipid separation and avoid the formation of undesired nitrogen compounds to produce higher-value products intended for human consumption.

ИЗМЕНЕНИЕ БЕЛКОВОГО СОСТАВА МОЛОКА КОРОВ ПРИ СУБКЛИНИЧЕСКОМ МАСТИТЕ

The nutritional value of milk and raw milk is determined by protein, so we paid special attention to determining the protein composition of raw milk. Were made measurements: the mass fraction of total nitrogen, the mass fraction of non-protein nitrogenous compounds, the content of urea, essential and non-essential amino acids. Biochemical studies of the protein composition of milk obtained from cows with suspected mastitis indicate that the content of total protein, casein, albumin and globulins in milk significantly changed with the growth of pathological processes in the mammary gland. Lactic cows underwent an express increase in the state of health, udder using Somatest manufactured and based on the result obtained, three groups of animals of 10 goals were formed. in everyone. 1st group detainees questionable test for Somatest express method; animals 2nd – weakly positive; the 3rd group included blood with a negative reaction to the tests. The difference in protein content was 5.71% (P < 0.05) and 3.27%; casein content – 13.27% (P < 0.001) and 11.98% (P < 0.05). According to the content of serum proteins, the opposite picture was observed, with the increase in udder pathology, the amount of albumins increased by 13.12% in the first group compared to the control; and by 26.39% – in the second group. In terms of the content of globulins, an increase was also noted in comparison with the control in the first group by 25.00% (P < 0.001) and 34.34% (P < 0.001). In milk samples of three test groups of animals, we identified 15 amino acids, of which 11 were essential and 4 non-essential. The test results indicate slight changes in the content of essential amino acids in cows with an increase in the inflammatory reaction in the udder. Diseases of the udder of cows are reflected in the quantitative ratio between the constituent parts of the protein fractions of milk, in particular, this is manifested in a decrease in casein, as well as in an increase in the content of whey proteins. Thus, the amount of casein needed to make cheese is reduced and whey protein is increased, making the milk unsuitable for cheese making.

Screening of Non-Protein Nitrogen Compounds in Lactose Refining Streams from Industrial Whey Permeate Processing

Screening of Non-Protein Nitrogen Compounds in Lactose Refining Streams from Industrial Whey Permeate Processing

Nonlinear modeling to describe the pattern of 15 milk protein and nonprotein compounds over lactation in dairy cows

The protein profile of milk includes several caseins, whey proteins, and nonprotein nitrogen compounds, which influence milk's value for human nutrition and its cheesemaking properties for the dairy industry. To fill in the gap in current knowledge of the patterns of these individual nitrogenous compounds throughout lactation, we tested the ability of a parametric nonlinear lactation model to describe the pattern of each N compound expressed qualitatively (as % of total milk N), quantitatively (in g/L milk), and as daily yield (in g/d). The lactation model was tested on a data set of detailed milk nitrogenous compound profiles (15 fractions-12 protein traits and 3 nonproteins-for each expression mode: 45 traits) obtained from 1,342 cows reared in 41 multibreed herds. Our model was a modified version of Wilmink's model, often used for describing milk yield during lactation because of its reliability and ease of parameter interpretation from a biological point of view. We allowed the sign of the persistency coefficient (parameter c) that explained the variation in the long-term milk component (parameter a) to be positive or negative. We also allowed the short-term milk component (parameter b) to be positive or negative, and we estimated a specific speed of adaptation parameter (parameter k) for each trait rather than assumed a value a priori, as in the original model (k = 0.05). These 4 parameters were included in a nonlinear mixed model with cow breed and parity order as fixed effects, and herd-date as random. Combinations of the positive and negative signs of the b and c parameters allowed us to identify 4 differently shaped lactation curves, all found among the patterns exhibited by the nitrogenous fractions as follows: the "zenith" curve (with a maximum peak; for milk yield and 10 other N traits), the "nadir" curve (with a minimum point; for 20 traits, including almost all those expressed in g/L of milk), the "downward" curve (continuously decreasing; for 14 traits, including almost all those in g/d), and the "upward" curve (continuously increasing; only for κ-casein, in % N). Direct estimation of the k parameters specific to each trait showed the large variability in the adaptation speed of fresh cows and greatly increased the model's flexibility. The results indicated that nonlinear parametric mathematical models can effectively describe the different and complex patterns exhibited by individual nitrogenous fractions during lactation; therefore, they could be useful tools for interpreting milk composition variations during lactation.

Studying the effect of pH, different concentrations of glutamic acid and salt on non-protein nitrogen compounds, survival and overall acceptance of low-fat probiotic cheese

Today, the demand for low-fat dairy products such as cheese has increased. Reducing fat in cheese reduces the sensory properties of cheese. The use of probiotic bacteria, fat alternatives and changes in production methods can improve the sensory properties of low-fat cheeses. The aim of this research is to investigate the effect of three independent variables including pH (4.7, 4.9 and 5.1), glutamic acid (1, 2, 3 mgg-1) and salt (2, 2.5 and 3%) on the amount of non-protein nitrogen compounds to total nitrogen, survival and overall acceptance of low-fat probiotic cheese during for 30 days’ storage. According to the results, the amount of non-protein nitrogen compounds to total nitrogen is increased during the ripening period in all samples, but this increase in the sample containing 2 mgg-1 glutamic acid, 2% salt and at pH 4.7 is significantly higher than other tested samples. The results are shown that with increasing the amount of glutamic acid and decreasing the amount of salt, the sensory properties and survival of probiotic bacteria is significantly increased. Probiotic bacteria are survived in all tested samples up to 30 days, but this survival is significantly more than other samples in the treatment containing 3 mgg-1 glutamic acid, 2% salt and at pH 4.9. The highest general acceptance score is belonged to the treatment containing 3 mgg-1 glutamic acid, 2% salt and pH 4.9, which was selected as the best treatment in terms of sensory and nutritional characteristics.

Use of Corn-Steep Water Effluent as a Promising Substrate for Lactic Acid Production by Enterococcus faecium Strain WH51-1

Various challenges facing the industrial production of bio-based lactic acid (LA) such as cost of raw materials and nitrogen sources, as well as contamination risk by mesophilic and neutrophilic producers, should be overcome for the commercial production. This study aimed to investigate the feasibility of corn steep water (CSW) as a raw material for LA production using a newly thermo-alkali-tolerant lactic acid bacterium. The physicochemical characteristics of CSW were investigated. The high carbohydrates, proteins, amino acids, vitamins, essential elements, minerals, and non-protein nitrogenous compounds content confirmed that the CSW is a promising substrate for LA production. Out of 67 bacterial isolates, Enterococcus faecium WH51-1 was selected based on its tolerance to high temperatures and inhibitory compounds (sodium metabisulfate, sodium chloride, sodium acetate, and formic acid). Fermentation factors including sugar concentration, temperature, inoculum size, and neutralizing agents were optimized for LA production. Lactic acid concentration of about 44.6 g/L with a high yield (0.89 ± 0.02 g/g) was obtained using 60 g/L of CSW sugar, inoculum size 10% (v/v), 45 °C, and sodium hydroxide or calcium carbonate as a neutralizing agent. These results demonstrated the potential of strain WH51-1 for LA production using CSW effluent as raw material.

Rehydration before Application Improves Functional Properties of Lyophilized Lactiplantibacillus plantarum HAC03.

Preservation of probiotics by lyophilization is considered a method of choice for developing stable products. However, both direct consumption and reconstitution of dehydrated probiotic preparations before application “compromise” the survival and functional characteristics of the microorganisms under the stress of the upper gastro-intestinal tract. We evaluated the impact of different food additives on the viability, mucin adhesion, and zeta potential of a freeze-dried putative probiotic, Lactiplantibacillus (Lp.) plantarum HAC03. HAC03-compatible ingredients for the formulation of ten rehydration mixtures could be selected. Elevated efficacy was achieved by the B-active formulation, a mixture of non-protein nitrogen compounds, sugars, and salts. The survival of Lp. plantarum HAC03 increased by 36.36% compared rehydration with distilled water (4.92%) after passing simulated gastro-intestinal stress conditions. Cell viability determined by plate counting was confirmed by flow cytometry. B-active formulation also influenced Lp. plantarum HAC03 functionality by increasing its adherence to a Caco-2 cell-line and by changing the bacterial surface charge, measured as zeta potential.Hydrophobicity, mucin adhesion and immunomodulatory properties of Lp. plantarum HAC03 were not affected by the B-active formulation. The rehydration medium also effectively protected Lp. plantarum ATCC14917, Lp. plantarum 299v, Latilactobacillus sakei (Lt.) HAC11, Lacticaseibacillus (Lc.) paracasei 532, Enterococcus faecium 200, and Lc. rhamnosus BFE5263.

Physicochemical properties and nutritional compositions of nipa palm (Nypa fruticans Wurmb) syrup

Nipa palm (Nypa fruticans Wurmb.) syrups from three geographical plantation sites in Nakhon Si Thammarat, Southern Thailand were characterized for their physicochemical properties and nutritional values. Variations in color, clarity, viscosity, pH, total soluble solid, total acidity, salinity, water activity, browning intensity and 5-hydroxymethylfurfural content of the syrups were observed among the plantation areas. The nutritional compositions of the syrups also varied depending on their harvested locations. Sugar was the main dry matter presented in all the nipa palm syrups, followed by protein and ash. The energy values of the syrups were in the range of 376–413 kcal/100 g, dw. Sucrose was found as a major sugar in all syrup whereas glucose and fructose were found as minor sugars. Low amounts of natural fructan, fructo-oligosaccharide, and kestose were found only in one plantation area. The total phenolic acid and total flavonoid contents were determined in all syrup with varying concentrations. Potassium and sodium were found as major elements. Phosphorus, magnesium, silica, calcium, iron, copper, iodine, manganese, zinc, and chromium were also found at varying contents. Sugar derivatives, non-protein nitrogenous compounds, polyphenols, organic acids, and some flavor substances were identified in the nipa palm syrups by liquid chromatography-mass spectrometry. Results highlighted the variations in physicochemical properties and nutritional compositions of nipa palm syrup. Overall, the nipa palm syrup can be regarded as an alternative sweetener for application in the functional food formulations.

Recent Developments in Seafood Packaging Technologies.

Seafood products are highly perishable, owing to their high water activity, close to neutral pH, and high content of unsaturated lipids and non-protein nitrogenous compounds. Thus, such products require immediate processing and/or packaging to retain their safety and quality. At the same time, consumers prefer fresh, minimally processed seafood products that maintain their initial quality properties. The present article aims to review the literature over the past decade on: (i) innovative, individual packaging technologies applied to extend the shelf life of fish and fishery products, (ii) the most common combinations of the above technologies applied as multiple hurdles to maximize the shelf life of seafood products, and (iii) the respective food packaging legislation. Packaging technologies covered include: Modified atmosphere packaging; vacuum packaging; vacuum skin packaging; active food packaging, including oxygen scavengers; carbon dioxide emitters; moisture regulators; antioxidant and antimicrobial packaging; intelligent packaging, including freshness indicators; time–temperature indicators and leakage indicators; retort pouch processing and edible films; coatings/biodegradable packaging, used individually or in combination for maximum preservation potential.

Analytical performance of Raman spectroscopy in assaying biochemical components in human serum.

Chronic non-infectious diseases are important to research as they are the main causes of death in Brazil and worldwide. One very important chronic non-infectious disease is cardiovascular disease, whose risk factors (diabetes, dyslipidemia, and renal failure) can be detected through assessments of serum biochemical components. The objective of this study was to evaluate the analytical performance of Raman spectroscopy for analysis of lipid profile (total cholesterol, triglycerides, and HDL cholesterol), non-protein nitrogenous compounds (urea and creatinine), and glucose in 242 human serum samples. Models to discriminate and quantify the samples were developed using the predicted concentration by quantitative regression model based on partial least squares (PLS). The analytical error for the "leave-one-out" cross-validation based on the predicted PLS concentration was 10.5 mg/dL for total cholesterol, 21.4 mg/dL for triglyceride, 13.0 mg/dL for HDL cholesterol, 4.9 mg/dL for urea, 0.21 mg/dL for creatinine, and 15.4 mg/dL for glucose. The Kappa coefficient indicate very good agreement for cholesterol (0.83), good for triglyceride (0.77), urea (0.70) and creatinine (0.66), and fair for HDL cholesterol (0.38) and glucose (0.30). The results of the analytical performance demonstrated that Raman spectroscopy can be considered an important methodology to screen the population, especially for serum triglycerides and cholesterol.

Powdered edible locust enhances nitrogen excretion and presents a low-energy value in growing rats

Abstract Edible insects are increasingly recommended as novel sustainable protein sources, but the nutritional properties of edible insects have not been well studied. We investigated whether locust powder can be used as a nutritionally functional food resource with a low energy value using a rat model. Twenty-five male Wistar rats (4-week-old) were fed a basal diet (12 g daily) to which a fixed amount of locust powder (0, 0.5, 1.0, or 2.0 g) was added for 20 days (L0, L0.5, L1.0, and L2.0 groups, respectively). In the sucrose standard group, rats received 12 g of the basal diet daily and 2.0 g of sucrose daily for 20 days (S2.0 group). Body-weight gain and the nutritional composition of the carcasses and feces were determined to estimate the available energy value of locust powder. The L0.5 group had the lowest carcass fat content and energy accumulation, but these values were increased by locust powder in a dose-dependent manner. The net energy value of locust powder was estimated to be 2.78 kcal/g, which was expected to be lower than the calculated theoretical value (4.25 kcal/g) and that of sucrose (3.94 kcal/g). Fecal nitrogen excretion was increased by dietary locust powder in a dose-dependent manner (correlation coefficient, R = 0.98), and the carcass nitrogen percentage was not changed, regardless of the dietary content of the locust powder, indicating an increased excretion of proteins or other non-protein nitrogen compounds derived from the locust powder. These findings suggest that locust powder can be used as a novel food material with a low energy value for humans.

Белковые и небелковые азотистые соединения молока. Методы контроля

Белковые и небелковые азотистые соединения молока. Методы контроля

A comparison of analytical methods for the determination of urea in yeast-based food and feed ingredients

ABSTRACTUrea is a non-protein nitrogen compound, authorised in the EU as a nutritional source of nitrogen in animal feed intended for ruminants with a functional rumen. The Rapid Alert System for Food and Feed (RASFF) is the EU online platform through which food and feed safety risks are reported. During 2017, several rapid alerts were raised in the EU by individual member states regarding the presence of unlabelled urea in feed-grade yeast. The presence of urea in animal feed is analysed with a spectro-colorimetric method, which is the EU official control method. Other urea analytical methods include enzymatic and LC-MS methods, which are also investigated in this study. The main objectives of this study were to analyse yeast feed-grade and food-grade products with independent laboratories using the EU official control method, as well as enzymatic and LC-MS methods. Comparison of results from the spectro-colorimetric, enzymatic and LC-MS methods for reliability, consistency and accuracy determined the most reliable method for the quantification of urea in animal feed. Yeast food and feed samples were tested using four independent laboratories. Results demonstrated a lack of consistency both within the same laboratory and between separate laboratories for urea quantification using the EU official control method. Urea quantification results for the AOAC 941.04 enzymatic method were found to be much higher than anticipated. The LC-MS method yielded the most consistent and reliable results. In conclusion, urea quantification by LC-MS analysis has the potential to be a viable method for urea analysis of yeast samples.