Influence of fermentation parameters on phytochemical profile and volatile properties of mulberry (Morus nigra) wine

In the present study Box–Behnken Design was employed to analyse the effects of fermentation parameters such as temperature (T _F), pH, inoculum size (I _S) and °Brix (B_X) on total phenolic concentration (TPC), total flavonoid concentration (TFC), total anthocyanin concentration (TAC), ethanol concentration (ETHC), total higher alcohol concentration (THAC) and total ester concentration (TESC) for the development of a phytochemical‐rich wine using mulberry as a substrate. The results demonstrated that fermentation parameters significantly alter the wine characteristics. Hence, a wine with excellent consumer preference (overall acceptability of 8.51) and high concentration of phytochemicals (TPC = 6014.03 ± 27.80 mg L⁻¹, TFC = 4791.35 ± 21.22 mg L⁻¹, TAC = 1480.72 ± 5.33 mg L⁻¹) as well as good aromatic properties (ETCH =82.85 ± 0.87 g L⁻¹, THAC =249.91 ± 0.31 mg L⁻¹ and TESC =52.55 ± 0.17 mg L⁻¹) with high antioxidant activity (DPPH =220.18 mmol·l⁻¹) was obtained at optimized fermentation conditions of T _F = 25°C, pH = 4.00, I _S = 10% (v /v) and B_X = 26. The results from the present study might contribute to strengthening the development of wine containing high concentrations of phytochemical compounds with attractive olfactory attributes. Copyright © 2017 The Institute of Brewing & Distilling     

INTERACTIVE EFFECTS OF SELECTED NUTRIENTS AND FERMENTATION TEMPERATURE ON H2S PRODUCTION BY WINE STRAINS OF SACCHAROMYCES

ABSTRACT

Metabolic interactions between yeast assimilable nitrogen (YAN), biotin, pantothenic acid, and fermentation temperature that affect H₂S production by wine yeast during alcoholic fermentation were examined. Strains of Saccharomyces cerevisiae (UCD 522 and EC1118) were inoculated into a synthetic grape juice medium with H₂S evolution monitored under fermentative conditions. While a number of interactions affected the evolution of H₂S, YAN as a factor by itself was found to be not significant (P > 0.05) for both yeasts examined. Maximal cumulative H₂S production for strain UCD 522 occurred in media fermented at 30C with 60 mg/L YAN, 10 µg/L biotin, and 50 µg/L pantothenic acid while minimum production was observed with 250 mg/L YAN and 250 µg/L pantothenate. Similarly, strain EC1118 produced the most H₂S at 30C, but with 250 mg/L YAN, 0.5 µg/L biotin, and 50 µg/L pantothenic acid and the least in media that contained 250 mg/L YAN and 250 µg/L pantothenic acid.

PRACTICAL APPLICATIONS

“Reduced” off‐odors of wines, primarily associated with sulfur‐containing molecules such as H₂S, continue to be a difficulty facing winemakers worldwide. One strategy for wineries to limit these problems is to add yeast nutrients prior to fermentation, most commonly, nitrogen‐containing compounds such as diammonium phosphate. However, nitrogen deficiency is not always the sole cause for these problems. Rather, the current research suggests the need to consider factors other than nitrogen including availability of biotin and pantothenic acid as well as fermentation temperature in order to minimize these off‐odors.     

The effect of nitrogen source on yeast metabolism and H2S formation

The impacts of aspartic acid and glutamine used as nitrogen supplements for alcoholic fermentations conducted by Saccharomyces were studied. Synthetic grape juice media and commercially prepared grape juices were supplemented with diammonium phosphate, aspartic acid, or glutamine to increase yeast-assimilable nitrogen concentrations to 250 mg N/L prior to fermentation. Two yeast strains, UCD522 and EC1118, were inoculated at 10⁵ CFU/mL and fermentations were monitored for soluble solids, hydrogen sulfide (H₂S), and residual amino acids. In general, unsupplemented media/juices fermented slower than supplemented ones, produced more H₂S, and contained lower concentrations of amino acids after fermentation. Among the supplemented treatments, fermentation rates, H₂S production, and amino acid utilization varied depending on the nitrogen source and yeast strain. Those fermentations supplemented with aspartic acid were generally slower and sometimes did not achieve dryness. In contrast, glutamine additions yielded fermentation rates and H₂S production equivalent or better than other supplemented treatments. Based on these results, the use of glutamine appears promising as an alternative nitrogen supplement for wine production.     

Effect of added sulphur dioxide levels on the fermentation characteristics of strawberry wine

The aim of this study to evaluate the effects of sulphur dioxide (SO₂) on strawberry wine fermentation and on the quality of the final wine product. Major aroma compounds, reducing sugars, ethanol, titratable acid and microflora were analyzed during the fermentation of strawberry wine supplemented with 0–100 mg/L SO₂. As the amount of added SO₂ increased, the consumption of reducing sugars and soluble solids and ethanol production decreased during early fermentation, but increased during late fermentation. During the fermentation process, the concentrations of 2‐phenethanol, isobutanol and isopentanol significantly increased and those of n‐propanol, isoamyl acetate and ethyl lactate decreased with increasing amount of added SO₂. The production of n‐butanol, ethyl acetate and ethyl butyrate was slightly dependent on the amount of added SO₂. Yeast cells were the dominant microbe in the fermenting strawberry pulp, and indigenous bacteria and fungi populations decreased rapidly or disappeared because of their sensitivity to SO₂. It was concluded that 60–80 mg/L SO₂ should be added during strawberry wine fermentations to improve wine quality. Copyright © 2016 The Institute of Brewing & Distilling     

Wine lees valorization: Biorefinery development including production of a generic fermentation feedstock employed for poly(3-hydroxybutyrate) synthesis

This study demonstrates the development of a novel wine lees (WL) based integrated biorefinery for the production of several added-value products. WL were initially fractionated for the production of antioxidants, tartrate and ethanol and the remaining stream was converted into a fermentation nutrient supplement for poly(3-hydroxybutyrate) (PHB) production using the strain Cupriavidus necator DSM 7237. Hydrolysis of pretreated WL was carried out using crude enzyme consortia produced via solid state fermentation of Aspergillus oryzae. Optimization of hydrolysis was based on the enhancement of total Kjeldahl nitrogen to free amino nitrogen (FAN) conversion yield by evaluating the effect of the initial pH value, temperature, initial proteolytic activity and initial WL concentration. WL hydrolysates and crude glycerol were used as nutrient and carbon sources, respectively, in batch and fed-batch fermentations for the production of PHB. Bacterial growth and PHB production were influenced significantly by the FAN content of the WL derived hydrolysates and by the addition of trace elements. Using an initial FAN concentration of 700 mg L^− 1 and supplementation with trace elements led to the production of 30.1 g L^− 1 of PHB concentration with an intracellular content of 71.3% (w w^-1) and a productivity of 0.56 g L^− 1 h^− 1 during fed-batch fermentation.     

The application of near‐infrared spectroscopy in beer fermentation for online monitoring of critical process parameters and their integration into a novel feedforward control strategy

Traditional methods used in the analysis of fermentation media suffer from a number of limitations. The search for more rapid and efficient methods has led to the development and application of near‐infrared spectroscopy. Near‐infrared spectroscopy has been applied successfully in a variety of industrial processes: agricultural, food, chemical and pharmaceutical, generally in the areas of raw material quality control but also including intermediate and finished product testing. The present research explores its potential for online fermentation monitoring of total cell count (TCC), specific gravity (SG), free amino nitrogen (FAN) and percentage alcohol by volume (% v v⁻¹) in a 300 L pilot‐scale validation batch. Models that were generated from three calibration batches for each of these constituents exhibited overall favourable standard error of cross validation (SECV) and fit of predicted vs actual cross validated results (SECV, R ²): SG (0.00072, 0.995), ethanol (0.17% v v⁻¹, 0.990), FAN (16.5 mg L⁻¹, 0.886) and TCC (1.24 × 10⁶ cells mL⁻¹, 0.640). The data that was most relevant to cell metabolism was determined to be sugar consumption rate, ethanol production rate, yield of ethanol and fermentation lag time. These ‘critical performance parameters’ were incorporated into a novel feed‐forward control strategy where yeast pitching rate was modified based on values of the critical performance parameters from the previous batch. Use of this feed‐forward strategy demonstrated how brewers can utilize near‐infrared monitoring for quality assurance through early detection of shifts in fermentation performance. Copyright © 2017 The Institute of Brewing & Distilling     

Development of low-alcohol isotonic beer by interrupted fermentation

Alcohol-free beer with isotonic properties is getting more popular and its production can be carried out by different production strategies; however, interrupted fermentation is still a challenge. Therefore, the objective of this study was to develop a low-alcohol isotonic beer (<0.5% v/v) by interrupted fermentation. Moreover, the major objective is to compare the developed product to commercial beverages (sports drinks, ‘Pilsen' regular beer, alcohol-free beers and low-alcohol isotonic beer). The beverages were evaluated based on pH, alcohol content (% v/v), total titratable acidity (mEq L⁻¹), osmolality (mOsmol kg⁻¹), bitterness International Bitterness Units, colour European Brewery Convention, total phenolic compounds (mg L⁻¹ gallic acid), reducing and total sugars (%) and Na and K contents (mg L⁻¹). The developed low-alcohol isotonic beer presented characteristics similar to sports drinks, with the advantage of being richer in phenolic compounds and suitable osmolality. Despite salts were added in its formulation, the grades attributed to all beers employed in the sensory evaluation, as well as the purchase intention did not present significant differences.     

Effects of nutrient supplementation on fermentation kinetics, H2S evolution, and aroma profile in Verdicchio DOC wine production

Different yeast nutrient additions were studied for the 2008 and 2009 vintages of Verdicchio grape juice fermentation. Addition of yeast derivatives at the beginning of fermentation and/or different amounts of diammonium phosphate at various times within the first half of fermentation were examined, with initial yeast assimilable nitrogen concentrations set at 200 and 250 mg l^?1. Supplementation with glutathione in combination with this nitrogen addition was also evaluated. Fermentation rates were monitored throughout these fermentations carried out under different nutrient conditions. H₂S production during fermentation and synthesis of volatile compounds in the finished wines were quantified; the wines also underwent sensory evaluation. The fermentation kinetics were almost exclusively influenced by the inorganic nitrogen supplementation with diammonium phosphate. H₂S evolution was more affected by assimilable nitrogen than glutathione. Diammonium phosphate significantly reduced H₂S production, with a further reduction in the presence of yeast derivative. This nitrogen supplementation yielded higher concentrations of acetate esters, and in particular of isoamyl acetate (fruity aromas), which positively influences the analytical and aroma profile of wines and results in a general reduction in 2-phenylethanol production (floral aromas). Overall results (two harvesting times and vintages) indicate that the management with diammonium phosphate and yeast derivative supplementation improves the kinetics of fermentation and provides a good tool to reduce H₂S formation and increase the analytical and sensory quality of Verdicchio wine.     

Effect of sulphur dioxide concentration added at different processing stages on volatile composition of ciders

This study evaluated the effect of sulphur dioxide (SO₂) added at different steps in the process on the volatile composition contributing to the fruity aroma of cider. Potassium metabisulphite was added (150 and 300 mg/L) at three processing steps (a) crushed apple, (b) apple must and (c) final product. The SO₂ added to the crushed apple either maintained or increased the fermentation rate, whereas the addition to the apple must slowed the fermentation rate. The addition of 300 mg/L of potassium metabisulphite to Golden Delicious apple must inhibited fermentation. The losses of volatile compounds varied from 23 to 46% and from 33 to 97% in all of the treatments with 150 and 300 mg/L of potassium metabisulphite, respectively. 3‐Methyl‐1‐butanol, acetaldehyde and ethyl ethanoate corresponded to >85% of the volatile compounds in the cider; 3‐methyl‐1‐butanol was not affected by the sulphur dioxide. Acetaldehyde showed the greatest reduction (>80%) with the addition of sulphur dioxide and ethyl ethanoate was reduced when the compound was added to the crushed apple and apple must. All of the interactions between the apple variety, the stage of SO₂ addition and the concentration of SO₂ showed significant negative impact on volatile compounds. © 2018 The Institute of Brewing & Distilling     

Optimization of Trace Metals Concentration on Citric Acid Production by Aspergillus niger NRRL 2001

Citric acid is nowadays produced by submerged fermentation of Aspergillus niger. The process yield depends on the composition of the medium, as well as on the microorganism strain. In this work, the effect of Fe⁺³, Zn⁺², and Mn⁺² on citric acid production by A. niger NRRL 2001 is presented. The culture medium composition was glucose (120 g/L) KH₂PO₄ (1.0 g/L); K₂HPO₄ (1.0 g/L), MgSO₄.7H₂O (0.5 g/L), (NH₄)₂SO₄ (3.0 g/L). The ions Fe⁺³, Zn⁺², and Mn⁺² had their concentrations changed according to an experimental design. The experiments were carried out in an orbital shaker at 200 rpm and 30°C. The strain produced an extracellular polysaccharide that was also quantified. The optimum experimental condition was found using 7.0 mg/L of Fe⁺³ and 6.5 mg/L of Zn⁺² in absence of Mn⁺². No oxalic acid formation was observed using this experimental condition. Metal contents were not significant for the production of the polysaccharide. The highest production rate (2.95 g L⁻¹ day⁻¹) was reached after 10 days of fermentation. After this period, the productivity decreased slightly. In 20 days, the citric acid production rate (2.44 g L⁻¹ day⁻¹) was 82% of the highest productivity. The conversion into citric acid increased continuously, yielding 45.8% in 20 days of fermentation.     

Multifactorial analysis of acetaldehyde kinetics during alcoholic fermentation by Saccharomyces cerevisiae

Acetaldehyde is the terminal electron acceptor in the alcoholic fermentation by Saccharomyces cerevisiae. Quantitatively the most important carbonyl by-product, it has relevance for ethanol production yields as well as product stabilization and toxicology. The aim of this study was to investigate the effect of various enological parameters on acetaldehyde kinetics during alcoholic fermentations. Two commercial yeast strains were tested in two grape musts and the pH, temperature, SO₂ and nutrient addition were varied. All incubations had uniform kinetics where acetaldehyde reached an initial peak value followed by partial reutilization. Peak acetaldehyde concentrations and residual concentrations after 15 days of fermentations ranged from 62 to 119 mg l^− 1 and 22 to 49 mg l^− 1, respectively. A positive linear relationship was found between peak and final acetaldehyde levels in Gewürztraminer, but not Sauvignon Blanc fermentations, where sluggish fermentations were observed. Several factors had a significant effect on peak and/or final acetaldehyde levels. SO₂ addition, grape cultivar and fermentation nutrition were important regulators of peak acetaldehyde production, while final acetaldehyde concentrations were correlated with SO₂ addition, grape cultivar and temperature. The results allowed to estimate the acetaldehyde increase caused by SO₂ addition to 366 ??g of acetaldehyde per mg of SO₂ added to the must. The course of the final fermentation phase was shown to determine acetaldehyde residues. Comparison of acetaldehyde and hexose kinetics revealed a possible relationship between the time of occurrence of peak acetaldehyde concentrations and the divergence of glucose and fructose degradation rates.     

Acid hydrolysis and fermentation of brewer's spent grain to produce xylitol

The hemicellulosic fraction of brewer's spent grain (BSG) was hydrolysed with diluted acid under different conditions of liquid/solid ratio (8–12 g g⁻¹), sulfuric acid concentration (100–140 mg g⁻¹ dry matter) and reaction time (17–37 min) in order to produce a liquor with a large amount of xylose and good fermentability to produce xylitol. Results showed that all the evaluated reaction conditions were able to hydrolyse xylan and arabinan with efficiencies higher than 85.8 and 95.7% respectively, and even under the mildest reaction condition a considerable amount (92.7%) of the hemicellulosic fraction could be extracted. The hydrolysates presented different fermentabilities when used as fermentation media for xylitol production by Candida guilliermondii yeast, owing to the differences in their composition. Based on statistical analysis, the best condition for BSG acid hydrolysis was the use of a liquid/solid ratio of 8 g g⁻¹, 100 mg H₂SO₄ g⁻¹ dry matter and a reaction time of 17 min. Under this condition a high extraction efficiency of hemicellulosic sugars (92.7%) and good fermentation results (Y_P/S = 0.70 g g⁻¹ and Q_P = 0.45 g dm⁻³ h⁻¹) were attained. Copyright © 2005 Society of Chemical Industry     

Saccharomyces cerevisiae associated with the spontaneous fermentation of tequila agave juice

Saccharomyces cerevisiae dominates the spontaneous fermentation of blue agave juice. Because of the batch heterogeneity, the aim of this work was to determine the strain diversity of S. cerevisiae among fermentations. During January and February 2015, agave juice was sampled in triplicate from four sampling points at a tequila distillery. The heterogeneity of yeast strains and the production of carbon dioxide were assessed during fermentation, whereas the amount of ethanol produced was measured at the end of the process. The fermentation cycle times varied widely (9 to 25 days), as did fermentation efficiency (2.5–45.5%). Yeast isolates were identified at the species level by ITS‐5.8S rRNA restriction fragment length polymorphism and differentiated at the strain level by random amplified polymorphic DNA. A total of 199 isolates were obtained and identified as S. cerevisiae, showing 69 different random amplified polymorphic DNA profiles. There was no clear dominance of any strain during fermentation. However, two strains (P1 and P2) were detected in all fermentation samples, suggesting their residency in the distillery, despite the deep‐cleaning applied to the tanks after each fermentation batch. According to the RAPD profiles, the number of strains isolated from fermentation samples increased from 17 in January to 25 in February. © 2018 The Institute of Brewing & Distilling     

Yeast population dynamics in five spontaneous fermentations of Malvasia must

The dynamics of the wine yeast strains presented in five spontaneous Malvasia wine fermentations have been studied. Samples were analysed for their microbiological characteristics and chemical substances. All 937 isolates were characterized using electrophoretic karyotyping and tested for their killer activity. The non- Saccharomyces population was identified using a combination of PCR-RFLP analysis of the rDNA spacer region and physiological testing. The total yeast population level in the must after sedimentation was 10⁵cfu ml⁻¹and included the following genera:Candida, Metschnikowia, Hanseniaspora, Rhodotorula, Issatchenkia and Debaryomyces. However, Saccharomyces sp. was not detected in fresh must samples plated on YEPD medium. Based on the chromosome length polymorphism among 649 isolates from the subsequent phases of fermentation, 46 different electrophoretic patterns of Saccharomyces cerevisiae were distinguished. The most abundant karyotypes were L₁, L₄, L₁₂, P₆. A sequential substitution of S. cerevisiae strains occurred during the different phases of fermentation. At the slow fermentation rate, karyotype L₄was most abundant in almost all fermenters. At the beginning of the tumultuous fermentation phase, the most frequent karyotype became L₁followed by karyotype L₄. Finally, during the fermentation process, pattern L₄was clearly replaced by karyotype L₁followed by pattern L₁₂. Despite the same fermentation source (grape must), differences among five spontaneous fermentations were observed. The population dynamics of S. cerevisiae yeasts, especially the dynamics of the major S. cerevisiae strains (L₁, L₄, and L₁₂) were quite similar in all five fermenters in opposite to the minor strains of S. cerevisiae.     

Use of spent brewer's yeast in L‐(+) lactic acid fermentation

The application of by‐products from the brewing industry in lactic acid (LA) production was investigated in order to replace expensive nitrogen sources (such as yeast extract) with cheaper and renewable nitrogenous materials such as brewer's yeast (BY). In this study, brewer's spent grain (BSG) hydrolysate was used for L‐(+)‐LA fermentation by Lactobacillus rhamnosus ATCC 7469. The effect of pH control during the fermentation and the addition of various BY contents (5–50 g/L) in BSG hydrolysate on fermentation parameters was evaluated. BY addition significantly increased free amino nitrogen (FAN) concentration (by 25.2% at 5 g/L to 616% at 50 g/L). A strong positive correlation between FAN concentration in the hydrolysate and concentration of L‐(+)‐LA produced was observed (correlation coefficient of 0.913). A high cell viability of L. rhamnosus ATCC 7469 (1.95–3.32 × 10⁹ CFU/mL at the end of fermentation) was achieved in all fermentations with the addition of brewer's yeast. The addition of BY increased L‐(+)‐lactic acid yield and volumetric productivity up to 8.4% (5 g/L) and 48.3% (50 g/L). The highest L‐(+)‐LA yield (89%) and volumetric productivity (0.89 g/L h^?1) were achieved in fermentation of BSG hydrolysate with 50 g/L of BY. © 2019 The Institute of Brewing & Distilling     

Comparison of the effect of pulsed electric field or high voltage electrical discharge for the control of sweet white must fermentation process with the conventional addition of sulfur dioxide

The present work discusses the efficiency of pulsed electrical treatments for the inactivation of yeasts. The application of pulsed electric fields (PEFs) and high voltage electrical discharges (HVEDs) as alternatives to sulfites, which are used as anti-microbial to stop the fermentation of sweet white wine, was investigated. The influence of sulfite concentration (from 0 mg·L^− 1 to 500 mg·L^− 1), PEF (from 4 kV·cm^− 1 to 20 kV·cm^− 1; from 0.25 ms to 6 ms) and HVED (40 kV/cm; 1 ms or 4 ms) treatments on the inactivation of total yeasts and non-Saccharomyces yeasts was determined. The addition of SO₂ (250 mg·L^− 1) resulted in 8 log total yeast reduction. The maximum yeast inactivation obtained with PEF and HVED was respectively 3 and 4 logs. The use of SO₂, HVED and PEF allows decreasing the non-Saccharomyces yeast level by 7, 5 and 4 logs respectively. However, the wine browning was less pronounced for the samples treated by PEF in comparison with HVED and SO₂ treatments. PEF seems to be the most suitable alternative technique to sulfite addition.     

Electrochemical sensing of total sulphites in beer using non‐modified screen‐printed carbon electrodes

An analytical method that combines gas‐diffusion microextraction with square‐wave voltammetric detection using commercial non‐modified screen‐printed carbon electrodes was employed in the determination of total sulphites in beer. The developed methodology showed low limits of detection (0.050 mg L⁻¹) and quantification (0.17 mg L⁻¹) and an intraday precision of 4.8%. The proposed method was also compared with a reference methodology used in the beer industry (EBC method 9.25.3) showing no significant differences in the obtained results. This is a simple, cheap and notably portable alternative for brewers that wish to quantify sulphites in their products. Copyright © 2017 The Institute of Brewing & Distilling     

Effects of sugar concentration on mango wine composition fermented by Saccharomyces cerevisiae MERIT.ferm

This study investigated the effect of initial sugar concentrations (^°Brix of 17, 23 and 30) on mango wine composition fermented by Saccharomyces cerevisiae MERIT.ferm. It was found that growth rate and maximum cell population were inversely correlated with initial sugar levels with the fastest growth rate and largest cell population in the low sugar fermentation. However, the cell population in the low and medium sugar fermentation declined significantly (from 8.7 and 8.2 log to 2 and 2.8 log, respectively) relative to the high sugar fermentation in which cell populations remained stable upon reaching the stationary phase (7.7 log). Glycerol production increased with increasing sugar content in low (13.4 g L^?1), medium (14.5 g L^?1) and high (15.9 g L^?1) sugar fermentation. In addition, high sugar fermentation had a negative impact on volatile production with significantly lower amounts of acetate esters (1.5 mg L^?1) but more acetic acid (0.54 g L^?1) compared to the low (5.0 mg L^?1 and 0.44 g L^?1, respectively) and medium (3.7 mg L^?1 and 0.49 g L^?1, respectively) sugar fermentations. Furthermore, volatiles especially terpene hydrocarbons (α‐caryophyllene was released) present in mango juice were significantly metabolised after fermentation, while numerous new volatile compounds (such as isobutyl alcohol, isoamyl alcohol, ethyl and acetate esters) were produced. Some terpene alcohols were released and converted into corresponding acetyl esters. This may indicate that the mango wines fermented with different levels of sugars would have different flavour aromas.     

The influence of vitamin E supplementation on yeast fermentation

Ethanol is a well‐known toxic metabolite of yeast, affecting cell growth, and it is a major factor responsible for reduced ethanol production. Therefore, yeast strains that can withstand high ethanol concentrations are highly desirable. The effects of vitamin E supplementation and enhanced cell membrane fluidity in ethanol fermentations were studied. The results showed that ethanol tolerance was significantly improved by vitamin E supplementation, which correlated with the increased level of polyunsaturated fatty acids. The data showed that, after 0.1 g L^?1 vitamin E was added to the highest ethanol concentration, one could attain 118.7 g L^?1, in contrast to 106.4 g L^?1. The experimental results indicated that the increase in vitamin E suppressed unsaturated fatty acid oxidation, resulting in enhanced ethanol tolerance and increased production yield. Copyright © 2016 The Institute of Brewing & Distilling     

Effect of debittering and solid-state fermentation processes on the nutritional content of lupine (Lupinus mutabilis Sweet)

There is a growing interest in vegetable-based sources of proteins. Despite its high nutrient content, lupine has been rarely exploited as a protein source due to the presence of high levels of non-nutritive compounds such as alkaloids, which impart a bitter taste. Here, we evaluated the effect of debittering and solid-state fermentation on the nutritional contents of three lupine varieties (Lupinus mutabilis Sweet). These processes induced significant changes (P < 0.05) in the nutritional composition of the three lupine varieties (INIAP-450, INIAP-451 and Criollo) and increased the protein levels to 644.55 g kg⁻¹ (Criollo variety) and the levels of several constituent amino acids such as valine (54.62 g kg⁻¹), methionine (42.47 g kg⁻¹), isoleucine (59.27 g kg⁻¹) and leucine (76.32 g kg⁻¹). The ether extract of INIAP-450 showed increased levels (up to 244.03 g kg⁻¹); especially, monounsaturated fatty acids (559.78 g kg⁻¹) and polyunsaturated fatty acids (293.17 g kg⁻¹) were observed. The omega-6/omega-3 ratio in the debittered grain oil reached the minimum requirement established for good-quality oils (5/1). However, the levels of other components decreased, showing levels up to 13.04 g kg⁻¹ (total starch) in the Criollo variety, 22.62 g kg⁻¹ (resistant starch) in INIAP-450, 6.53 g kg⁻¹ (potassium) in INIAP-451, 46 g kg⁻¹ (iron) in INIAP-451 and 29.75 g kg⁻¹ (zinc) in INIAP-450.