Free Amino Nitrogen Research Articles

Evaluation of different validation strategies and long term effects in NIR calibration models

Stable and reliable NIR calibration models for the barley malt quality assessment were developed and exhaustively evaluated. The measured parameters are: fine extract, fermentability, pH, soluble nitrogen, viscosity, friability and free-amino nitrogen. The reliability of the developed calibration models was evaluated comparing the classic leave-one-out internal validation with a more challenging one exploiting re-sampling scheme.The long-term effects, intended as possible alterations of the NIR method predictive power, due to the variation between samples collected in different years, were evaluated through an external validation which demonstrated the stability of the developed calibration models.Finally, the accuracy and the precision of the developed calibration models were evaluated in comparison with the reference methods.This exhaustive evaluation offers a realistic idea of the developed NIR methods predictive power for future unknown samples and their application in the beer industry.

Influence of lactic acid bacteria on redox status and on proteolytic activity of buckwheat (Fagopyrum esculentum Moench) sourdoughs

Redox potential and proteolysis determine protein networks in doughs and thus dough rheology as well as the structure of baked goods. Namely, gluten-free bakery products needs structural improvements but little is known about these parameters in gluten free dough systems. In this work the influence of lactic acid bacteria (LAB) on redox status and proteolysis of buckwheat sourdoughs was investigated. An increase of free thiol groups was detected as redox potential was decreasing during fermentation. Thiol content at 8h was higher in doughs fermented with strains with high reductive activity, such as Weissella (W.) cibaria in comparison to Pediococcus (P.) pentosaceus, which exhibited a lower reducing activity. At 24h each fermentation showed a similar content of free thiol groups. Endogenous buckwheat proteases were characterized using various protease inhibitors in buckwheat doughs. Until pH3.1 a proteolysis increase was monitored in doughs. Employed LAB didn't show any detectable extracellular proteolytic activity. Flour proteases are thus responsible for protein breakdown, and this was demonstrated comparing free amino nitrogen (FAN) values and protein electrophoretic patterns of sourdough fermentations with chemical acidified (CA) doughs. FAN content at 24h using P. pentosaceus, proteolytic comparative strain of Enterococcus faecalis, W. cibaria, mixed culture (containing P. pentosaceus and W. cibaria), CA and CA doughs containing glutathione (GSH) reached 45.9±1.3, 42.4±1.3, 40±1, 31±2, 29±2 and 17.8±3.9mmolkg−1 flour, respectively. Proteolysis was mainly influenced by pH and incubation time. The addition of GSH showed a decrease of proteolysis and of free amino acids. CA doughs showed a higher total free amino acids content than sourdough fermented with LAB indicating their metabolization. Fermentations with high FAN values exhibited lower band intensity (analyzed under reducing condition) in electrophoretic patterns. These results show that dough proteases are responsible for proteolysis in buckwheat sourdoughs and this activity is influenced from LAB metabolism. Moreover, oxidation–reduction potential (ORP) changes do not show improvements of proteolytic activity in buckwheat sourdoughs.

The World's Most Popular Assay? A Review of the Ninhydrin-Based Free Amino Nitrogen Reaction (FAN Assay) Emphasizing the Development of Newer Methods and Conditions for Testing Alcoholic Beverages

This review covers what is, arguably, the world's most widely used food industry-related assay, the ninhydrin reaction, for the determination of the free amino nitrogen content of biological materials, including beverages and foods. This assay, for application to beer and wine samples, was adapted for use in a multi-well format and demonstrated the potential to scale down and run more multi-well tests in brewing quality control testing laboratories. Scaling down brewery laboratory tests reduces demands for expensive reagents, limits waste, and makes for simpler, less expensive disposal, while also giving a faster turnaround of results for many assays. In redefining the ninhydrin free amino nitrogen assay for use with modern instruments, we rediscovered the most efficient reagents and optimal conditions for application of this test in the contemporary brewing laboratory. Six critical parameters for ninhydrin reactions (buffer composition, incubation time, temperature, pH, assay volume, and reducing agent) have been reassessed with a new microwell assay combining all of them, now providing high precision and sensitivity. Finally, new reduced volume and microwell-based FAN assay formats should prove useful to many brewing, enology, distilling, and food laboratories for the routine determination of free or total useable nitrogen, and for further refinement and optimization of this important assay.

Food waste as nutrient source in heterotrophic microalgae cultivation

Glucose, free amino nitrogen (FAN), and phosphate were recovered from food waste by fungal hydrolysis using Aspergillus awamori and Aspergillus oryzae. Using 100g food waste (dry weight), 31.9 g glucose, 0.28 g FAN, and 0.38 g phosphate were recovered after 24h of hydrolysis. The pure hydrolysate has then been used as culture medium and nutrient source for the two heterotrophic microalgae Schizochytrium mangrovei and Chlorella pyrenoidosa, S. mangrovei and C. pyrenoidosa grew well on the complex food waste hydrolysate by utilizing the nutrients recovered. At the end of fermentation 10-20 g biomass were produced rich in carbohydrates, lipids, proteins, and saturated and polyunsaturated fatty acids. Results of this study revealed the potential of food waste hydrolysate as culture medium and nutrient source in microalgae cultivation.

Hardness Changes and Endosperm Modification During Sorghum Malting in Grains of Varying Hardness and Malt Quality

ABSTRACTThis study examined the interaction between sorghum grain hardness and sorghum malt quality in terms of diastatic power and free amino nitrogen with endosperm modification during malting. The changes in kernel hardness during malting of four commercial sorghum cultivars of differing quality in terms of endosperm texture and potential malt quality were measured using tests for hardness and density, and endosperm modification was followed by scanning electron microscopy. The general pattern of modification during sorghum malting was confirmed to start at the endosperm–scutellum interface and then continue into the floury endosperm toward the kernel distal end. Significantly, a cultivar of intermediate hardness and low malting quality remained harder and modified more slowly than a harder cultivar of high malting quality. It appeared that intrinsic grain hardness and malt amylase and protease activity both affected malt hardness and endosperm modification, but amylase and protease activity had a greater effect because of their degradation of endosperm starch and protein. Of the hardness and density tests studied, the tangential abrasive dehulling device (TADD) gave the best measure of hardness throughout malting; maximum range was 24–100% kernel removed over five days of malting. Also, the data agreed with the observed malt modification rates. Thus, the TADD may have application as a simple and rapid test for estimating sorghum malt quality.

Utilisation of By-Products from Sunflower-Based Biodiesel Production Processes for the Production of Fermentation Feedstock

By-products streams from a sunflower-based biodiesel plant were utilised for the production of fermentation media that can be used for the production of polyhydroxyalkanoates (PHA). Sunflower meal was utilised as substrate for the production of crude enzyme consortia through solid state fermentation (SSF) with the fungal strain Aspergillus oryzae. Fermented solids were subsequently mixed with unprocessed sunflower meal aiming at the production of a nutrient-rich fermentation feedstock. The highest free amino nitrogen (FAN) and inorganic phosphorus concentrations achieved were 1.5 g L−1 and 246 mg L−1, respectively, when an initial proteolytic activity of 6.4 U mL−1 was used. The FAN concentration was increased to 2.3 g L−1 when the initial proteolytic activity was increased to 16 U mL−1. Sunflower meal hydrolysates were mixed with crude glycerol to provide fermentation media that were evaluated for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) using Cupriavidus necator DSM 545. The P(3HB-co-3HV) (9.9 g l−1) produced contained 3HB and 3HV units with 97 and 3 mol %, respectively. Integrating PHA production in existing 1st generation biodiesel production plants through valorisation of by-product streams could improve their sustainability.

Effect of Carbon Dioxide Injection on Physiochemical Properties and Saccharification of Extruded Corn Starch for Fermentation Substrate Preparation

The objective of this research was to investigate the effect of carbon dioxide injection during extrusion process at different melt temperatures 95, 115 and 135°C on physiochemical properties and enzymatic saccharification of extruded corn starch for fermentation substrate preparation. Carbon dioxide gas was injected during extrusion at the flow rate of 500 ml/min and pressure of 3 MPa. For enzymatic saccharification, 0.8% α-amylase enzyme was used at different saccharification periods. After extrusion, physiochemical properties and reducing sugar content were measured. Carbon dioxide injection had positive effects on breaking strength, elastic modulus, expansion ratio, specific length, piece density, water absorption index, water solubility index, free amino nitrogen and reducing sugar content (after saccharification) at melt temperatures 115 and 135°C. However, significant decrease (p<0.05) in specific mechanical energy input was obtained at only 135°C. The data clearly showed that carbon dioxide injection gave significantly increased (p<0.05) reducing sugar content at melt temperatures 115 and 135°C for fermentation substrate preparation.

The Influence of Glumes on Malting and Brewing of Hulled Wheats

The composition and malting behaviors of different malts and worts of the hulled wheat varieties Rossorubino (Triticum dicoccum) and Monlis (T. monococcum) malted with and without glumes were studied. During malting, acrospires were removed together with the rootlets after kilning from the dehulled samples, whereas only the rootlets were removed from the hulled samples. The malt analysis revealed that the hulled malts exhibit lower soluble protein content with higher free amino nitrogen and total free amino acid values. The amount of the dimethyl sulfide precursors was lower in the dehulled malts than in the hulled ones. Based on its positive malt parameters, Rossorubino was chosen to produce three beers: a 100% hulled Emmer malt beer and, mixed with barley malt, a 40% hulled Emmer malt beer and a 40% dehulled Emmer malt beer. The technological parameters of the relative beers were in the standard range. The 100% hulled Emmer malt beer showed a lower polyphenol content than the barley malt beers and had good foam stability. The descriptive sensory analysis showed that all descriptors were present in the 100% Rossorubino beer with medium-low scores. All panelists observed a refreshing character with notes of honey and a floral, citric aroma of the beer.

Production of Brewing Worts from Different Types of Sorghum Malts and Adjuncts Supplemented with β-Amylase or Amyloglucosidase

Sorghum has been used in beer production despite its lower diastatic activity. However, it is viewed as an excellent choice for the production of gluten-free beers. In this research, worts produced with white or red sorghum malts and waxy or regular sorghum adjuncts, supplemented with β-amylase or amyloglucosidase, were evaluated using barley malt as control. Soaking and germination times to optimize sorghum diastatic activity were determined, and characterization of raw materials was assessed. Worts were obtained by a double-mashing procedure following combinations of malts, adjuncts, and extrinsic enzymes. Between sorghums, the red sorghum malt had the highest total amylolytic activity and yielded higher amounts of fermentable carbohydrates in worts compared with the white sorghum malt counterparts, especially when mashed with refined waxy sorghum adjuncts. Barley malt yielded up to 24% more wort adjusted to 12°P and similar free amino nitrogen and pH values compared with their counterparts produced with sorghum malts. As expected, the addition of β-amylase increased the amount of fermentable sugars in the sorghum malt worts. When amyloglucosidase was added, the total sugar content augmented 20%, the glucose content was five times higher compared with worts without exogenous enzymes, and treatments were comparable regardless of the malt type.

톳 발효 추출물을 이용한 고추장의 영양학적 특성

톳 발효 추출물을 첨가하여 개량식 방법으로 고추장을 제조하고 이에 따른 성분분석을 측정하였다. 일반성분 분석에서 톳 발효 추출물 첨가 고추장 및 일반 고추장을 비교하였을 때 조단백, 조지방 및 탄수화물등은 비슷한 함량을 나타내었다. 아미노산 분석 결과 총 아미노산 함량은 톳 발효 추출물 첨가 고추장이 15,929.5 ng/mg이며 일반 고추장이 14,965.6 ng/mg으로 톳 발효 추출물 첨가 고추장이 일반 고추장에 비해 더 높았다. 아미노태질소분석시 일반 고추장의 경우 1044.80 mg%로 나타난 반면에 톳 발효 추출물 첨가 고추장의 경우 1715.88 mg%로 매우 높은 함량을 나타내었다. 일반 고추장과 톳 발효 추출물 첨가 고추장의 식염은 각각 15.97%, 6.12%로 나타났으며 무기질은 톳 발효 추출물 첨가 고추장이 칼슘이 더 많았으며, 나트륨 함량은 일반 고추장에 비해 현저하게 낮았다. The nutritional properties of the Kochujang were investigated with Fermented Extract of Hizikia fusiforme. No big differences in proximate compositions(moisture, Crude protein, Crude fat, and Crude ash, Carbohyrate) were observed between Two kinds of kochujangs tested in this study, general kochujang purchased from a market(GK), kochujang added with Fermented Extract of Hizikia fusiforme(FGK). However, FGK showed higher level of Total free amino acid(15,929.5 ng/mg), amino nitrogen(1715.88 mg%) and mineral contens than GK. the analysis of volatile compounds using GC/MS revealde than the fermentation dramatically removed off-flavors such as Acetaldehyde, Silane rimethyl(2-methylphenyl)-, 1H-Indole 2-phenyl-1-(trimethylsilyl) in Fermented Extract of Hizikia fusiforme(FGK).

Valorisation of bakery waste for succinic acid production

In this paper, bakery waste, including cakes and pastries from Starbucks Hong Kong, was evaluated for the potential of succinic acid (SA) production. Through simultaneous hydrolysis and fungal autolysis, both cake and pastry hydrolysates were found to be rich in glucose (35.6 and 54.2 g L−1) and free amino nitrogen (685.5 and 758.5 g L−1), whereas the protein hydrolysis yields were 23.2 and 22.5%, respectively. These cake and pastry hydrolysates, together with magnesium carbonate (10 g L−1) were subsequently used as feedstock in Actinobacillus succinogenes fermentation, and the resultant SA concentrations were 24.8 and 31.7 g L−1, respectively. A cation-exchange resin-based process (via vacuum distillation and crystallisation) was subsequently used to recover the SA crystals from fermentation broth, and a high SA crystal purity (96–97.7%) was obtained. Results of the present work successfully demonstrated the novel use of bakery waste as the generic feedstock for the sustainable production of SA as a platform chemical in food waste biorefinery.

Evaluation of by-products from the biodiesel industry as fermentation feedstock for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production by Cupriavidus necator

Utilization of by-products from oilseed-based biodiesel production (crude glycerol, rapeseed meal hydrolysates) for microbial polyhydroxyalkanoate (PHA) production could lead to the replacement of expensive carbon sources, nutrient supplements and precursors for co-polymer production. Batch fermentations in shake flasks with varying amounts of free amino nitrogen led to the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) with a 2.8–8% 3HV content. Fed-batch fermentations in shake flasks led to the production of 10.9g/L P(3HB-co-3HV) and a 55.6% P(3HB-co-3HV) content. NaCl concentrations between 2 and 6g/L gradually became inhibitory to bacterial growth and PHA formation, whereas in the case of K2SO4, the inhibitory effect was observed only at concentrations higher than 20g/L. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and nuclear magnetic resonance (13C NMR) demonstrated that the incorporation of 3HV into the obtained P(3HB-co-3HV) lowered glass transition temperature, crystallinity and melting point as compared to polyhydroxybutyrate. Integrating PHA production in existing oilseed-based biodiesel plants could enhance the viability and sustainability of this first generation biorefinery.

Effect of Germination Temperatures on Proteolysis of the Gluten-Free Grains Rice and Buckwheat during Malting and Mashing

This study examined the performance of rice and buckwheat when malted under various temperature conditions and for different lengths of time. The mashed malts produced from both rice and buckwheat contained a wide spectra of sugars and amino acids that are required for yeast fermentation, regardless of malting temperature. At the germination temperatures of 20, 25, and 30 °C used, production of reducing sugars and free amino nitrogen (FAN) followed similar patterns. This implies that temperature variations, experienced in different countries, will not have an adverse effect on the production and release of amino acids and sugars, required by yeast during fermentation, from these grains. Such consistency in the availability of yeast substrates is likely to reduce differences in processing when these malts are used for brewing. This study revealed that, while rice malt consistently produced more maltose than glucose, buckwheat malt gave several times more glucose than maltose, across all germination temperatures. Buckwheat malt also produced more soluble and free amino nitrogen than rice malt. Unlike sorghum, which has gained wide application in the brewing industry for the production of gluten-free beer, the use of rice and buckwheat is minimal. This study provides novel information regarding the potential of rice and buckwheat for brewing. Both followed similar patterns to sorghum, suggesting that they could play a similar role to sorghum in the brewing industry. Inclusion of rice and buckwheat as brewing raw materials will increase the availability of suitable materials for use in the production of gluten-free beer, potentially making it more sustainable, cheaper, and more widely available.

Fate of free amino nitrogen during liquefaction and yeast fermentation of maize and sorghums differing in endosperm texture

Biofuels demands have motivated the increasing research in production technology as well as effective raw material utilization. Fusel alcohol production had been related with the free amino nitrogen (FAN) content produced during hydrolyses stages and also as a stress response of Saccharomyces cerevisiae. This paper analyses the effect of grain type and endosperm texture on FAN production during starch liquefaction and yeast fermentation of maize, white and red sorghums bioconverted into ethanol. The white sorghum had a harder endosperm texture and upon milling produced a coarser granulation compared to the red counterpart. Therefore, the red sorghum produced higher amounts of FAN during liquefaction and the kinetics of these nitrogenous compounds were metabolized faster during the first hours of yeast fermentation. The white and red sorghums yielded 13.6% and 2.7% lower ethanol compared to the maize counterpart. The white sorghum yielded the lowest amount of ethanol likely to its relatively harder endosperm texture that was less susceptible to biocatalysis and yeast fermentation.

Solid-State Fermentation of Wheat Pieces by Aspergillus oryzae: Effects of Microwave Pretreatment on Enzyme Production in a Biorefinery

Production of hydrolytic enzymes is crucial to operate successful cereal-based biorefineries, where macromolecules in cereals (such as starch, protein, and phosphorus), are converted into their monomers (glucose, free amino nitrogen, and free phosphorous, respectively) for the production of different value-added products. In this study, effects of microwave pretreatment on enzyme production during solid-state fermentations of wheat pieces by Aspergillus oryzae were studied. Results showed that microwave pretreatment for a duration of 30 seconds increased glucoamylase and protease activities from 20 and 143 U/g (db, dry basis), in the control experiment, to 32 and 179 U/g (db), respectively.

Physicochemical characterization of starches from some Nigerian and Chinese roots and tubers

Chemical changes during germination and malting characteristics of six Nepalese finger millet varieties (GPU 0025, GE 5016, Dalle, Okhle, Kabre and Juwain) were studied. Millets were steeped in water at room temperature overnight, germinated for 48 h at 28±1°C, kilned at 50±2°C for 24 h and then, chemical characteristics of unmalted and malted millets were analyzed. Germination increased (p<0.05) total reducing sugar and glucose contents in all millet varieties. Starch, amylose and amylopectin contents in unmalted millets were between 71.32 to 79.86, 20.39 to 24.13, and 49.11 to 55.72% dry basis (db) respectively; whereas, those of malted millets were 63.74 to 67.12, 16.62 to 19.27 and 44.47 to 50.18% (db) respectively. Similarly, total phenolics (as gallic acid), total flavonoids (as rutin) and tannin (as tannic acid) contents in unmalted millets ranged from 60.9 to 229.2, 35.2 to 141.7 and 169.9 to 566.0 mg% (db) respectively; whereas, the values in malted millets were 123.1 to 247.8, 50.1 to 236.3 and 173.7 to 301.8 mg% (db) respectively. Except in GE 5016 and Juwainmillets, malting decreased (p<0.05) antioxidant activity in other varieties. Malt extract analysis revealed that all malt extracts possessed aromatic odor and showed negative starch-iodine test. Filtration rate of Juwain malt extract was slow but it was normal in other extracts. The color (EBC unit), free amino nitrogen (FAN) (mg% as glycine) and total reducing sugar (% m/v as maltose) contents in extracts were 2.77 to 5.78, 2.6 to 9.0 and 4.50 to 6.93, respectively. Glucose (%, m/v) and extract yield of malt (%, db) ranged from 1.22 to 2.51 and 80.20 to 88.83, respectively. Total soluble solids (TSS) (o Bx), pH, extract (%, m/m), FAN (mg% m/v) and total reducing sugar (% m/m as maltose) in worts derived from Dalle, Kabre and Juwain millet malts were in the range of 12.43 to 13.07, 5.44 to 5.66, 12.0 to 12.7, 19.5 to 20.3 and 7.64 to 10.45, respectively. Key words: Millet malt, amylose, polyphenols, free amino nitrogen (FAN), antioxidant activity, malt extract, wort.

Impact of Various Levels of Unmalted Oats (Avena Sativa L.) on the Quality and Processability of Mashes, Worts, and Beers

The brewing industry is facing an ever increasing challenge to become more cost-effective, while at the same time maintaining or improving product quality. Brewing with unmalted oats (Avena sativa L.) has the potential to reduce the costs of raw materials. However, the replacement of malted barley with unmalted oats can also adversely affect the quality and processability of mashes, worts, and beers. In this study, brewing with unmalted oats (0–40%) and malted barley was carried out in a 60-L pilot plant. The impact of various levels of oats on mashing, lautering, and fermentation performance was monitored in detail and the quality of the final beers was evaluated using Lab-on-a-Chip capillary electrophoresis as well as standard methods specified by Mitteleuropäische Brautechnische Analysenkommission (MEBAK), European Brewery Convention (EBC), or the American Society of Brewing Chemists (ASBC). It has been found that the β-glucan content and viscosity of mashes and worts increased significantly with increasing amounts of oats. In addition, the use of 20% or more oat adjunct resulted in a clearly increased lautering time. The replacement of barley malt with unmalted oats also had adverse effects on total soluble nitrogen (TSN), free amino nitrogen (FAN), and extract levels in worts. The foam stability of the final beers decreased significantly using 20% oats or more. However, their sensory quality improved with increasing levels of oat adjunct.

The Importance of Wort Composition for Yeast Metabolism during Accelerated Brewery Fermentations

The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e., higher inoculum level). Next to this, high-gravity brewing has become a standard strategy for brewers to increase their productivity. However, both technologies can have a significant effect on yeast metabolism. In this study, high-gravity and high-cell-density fermentations were combined, and their impact on yeast physiology and flavor compound production was evaluated. Additionally, an attempt was made to decrease the production of total diacetyl during accelerated fermentation systems by optimization of the free amino nitrogen content of the wort. Higher wort density resulted in decreased yeast viability, which correlated to increased expression levels of stress-related genes and higher levels of trehalose. More than wort density, the relative amounts of different assimilable sugars have a drastic effect on both yeast fermentation performance and flavor compound production. Worts with high amounts of sucrose had a stimulating effect on the uptake of amino acids, yeast growth, glycogen formation, recycling of trehalose, ethyl ester synthesis, and the turnover rate of total diacetyl. Yeast exposed to high levels of sucrose experienced more osmotic stress and stress related to stationary phase than other high-gravity worts. Although sucrose, compared with maltose, had a stimulating effect on ATF1 expression, a remarkable decrease in acetate esters was observed. Considering the adverse effects of sucrose on the yeast performance, it is advisable to avoid high concentrations of these fast-food sugars and to use a combination of sucrose and maltose syrups as a way to increase the wort density.

The influence of unmalted barley on the oxidative stability of wort and beer

The aim of this study was to investigate the influences of unmalted barley on the brewing process and the quality of the resulting beer-like beverages, with the main focus on the oxidative stability, using traditional beer analyses, GC-MS for the determination of aging compounds and electron paramagnetic resonance spectroscopy to determine free radical activity. For the investigation, brews with different barley proportions and 75% barley brews with a colour malt addition, to compensate for a lower colour using barley, were produced. In general, it can be said that beers with a proportion of up to 50% barley achieved a comparable or higher extract yield and final attenuation owing to the combined effectiveness of the malt and microbial enzymes. Although all analytical values were within the normal range according to Methodensammlung der Mitteleuropaischen Brautechnischen Analysenkommission (MEBAK), a slight decrease in total polyphenols and free amino nitrogen content was observed. Also in response to higher barley portions, an increase of higher molecular weight proteins and β-glucan was detected. Barley is not exposed to heat and oxidative stress in the malting plant, which explains the lower values of the thiobarbituric acid index and colour as an indicator of Maillard reaction products in the resulting wort and beer. Additionally, the results demonstrate a slower increase of aging compounds during beer storage with increasing barley proportions. Furthermore, it was observed that higher barley proportions led to a better oxidative stability indicated by a lower radical generation (T450-value) in wort and an increasing beverage antioxidant index/endogenous antioxidative potential (BAX/EAP value) in the final beverage. The case of ‘barley beers’ showed that the positive effect of barley on the oxidative beer stability was greater than the negative effect of the addition of colour malt, to adjust the colour of a 100% malt beer. In sensory comparison with beer produced with 100% malt, the beers brewed with a barley proportion up to 50% showed a slight flavour preference and up to a 75% equivalent evaluation. Copyright © 2012 The Institute of Brewing & Distilling

Potential for improvement in yeast nutrition in raw whole grain sorghum and maize lager brewing and bioethanol production through grain genetic modification and phytase treatment

Brewing and bioethanol production with raw grain and exogenous enzymes produces wort with satisfactory hot water extract (HWE). However, the free amino nitrogen (FAN) and mineral content can be too low, owing to low protein digestibility (PD) and phytate–mineral chelation, respectively. This study evaluated the potential for improvement in yeast nutrition in raw whole sorghum and maize brewing and bioethanol production by genetic modification (GM) of sorghum to improve PD and reduce phytate content, and by treatment with exogenous phytase. While phytase addition decreased sorghum spent grain phytate content (88%) and content of minerals (17 to 59%; i.e. increased wort mineral content), it did not affect maize phytate spent grain mineral content or HWE significantly. However, phytase addition did increase maize wort FAN (20%), sorghum HWE (2.8 percentage points) and wort FAN (23%). GM sorghum gave reduced spent grain mineral contents (11–38%), increased HWE (5.5 percentage points) and wort FAN (71%). Hence, genetic modification of sorghum to improve PD and reduce phytate content has considerable potential in raw grain brewing and bioethanol production to improve yeast nutrition. Copyright © 2012 The Institute of Brewing & Distilling