Characterisation of protein‐rich isolates and antioxidative phenolic extracts from pale and black brewers' spent grain

Protein‐enriched isolates and co‐product fractions were obtained from sheared, pale and black brewers' spent grain (BSG) using sequential aqueous and alkaline (110 mm NaOH) extraction, followed by isoelectric precipitation at pH 3.8. A recovery of 59% of the original pale BSG protein and 15% of the black BSG protein was obtained for the final isolates. Gel permeation HPLC (GP‐HPLC) revealed that 59% of the extracted pale BSG protein and only 6% of black BSG protein had a molecular mass >10 kDa. Glutamine/glutamate and proline were the most abundant amino acids present in both isolates. Analysis of four co‐product fractions obtained during fractionation from both pale and black BSG revealed the presence of phenolics, with higher concentrations in the black BSG extracts. These fractions possessed antioxidant and free radical scavenging activity when tested using the ferric reducing ability of plasma (0.16 ± 0.01 to 4.33 ± 0.11 mg Trolox equivalents g^?1 BSG dry weight) and diphenylpicrylhydrazyl (12.85 ± 1.16% to 59.50 ± 3.47% DPPH?_sc) assays, respectively. The protein‐enriched isolates and the phenolic‐rich extracts may find use as value‐added ingredients for incorporation into conventional and functional foods.     

Nonprotein nitrogen content of defatted jojoba meals

Extraction of defatted jojoba meals with 0–5 M triehloroacetic acid solutions revealed a minimum solubility of nitrogenous compounds in the range of 0.5–2 M . This minimum was assumed to correspond to the nonprotein nitrogen (NPN) fraction. Trichloroacetic acid concentrations of 0.8–1.0 M were found to be optimal for NPN determination. NPN values for laboratory-prepared meals ranged from 21 to 29% of the total nitrogen for undecorticated (with seed coat) meals and from 21 to 30% for decorticated (without seed coat) meals. Commercial presscakes and presscake fines ranged from 15 to 20% of total nitrogen as NPN. These lower values apparently reflect heat treatments received by the presscakes during commercial expelling of the jojoba liquid wax esters, In aqueous dispersions of unheated jojoba meals, nitrogenous compounds exhibited a minimum solubility of 23–45% of total nitrogen at pH 3–4, the apparent isoelectric region of the storage proteins. In some meals NPN comprised up to 100% of the nitrogen soluble at this minimum; thus, low yields of recoverable meal nitrogen in the form of protein isolates are predicted. The NPN fraction was characterized by amino acid analysis and gel electrophoresis and found to contain free amino adds, peptides, and polypeptides of 6–10 kDa. Simmondsin and its derivatives are estimated to make up about one-third of the NPN.     

THE RELATIVE CONTRIBUTIONS TO WORT NITROGEN OF NITROGENOUS SUBSTANCES SOLUBILIZED DURING MALTING AND MASHING

Treatment of ground malt with boiling ethanol fails to inactivate proteolytic and amylolytic enzymes completely, whereas boiling aqueous ethanol (80% v/v) is effective. Proteolytic activity during infusion mashing of all-malt grists is responsible for the production of nearly half of the nitrogenous compounds and amino nitrogen of wort. The percentage of the nitrogen solubilized during malting and mashing which consists of amino nitrogen is almost identical in the two processes.     

Development of an Aqueous Polyethylene Glycol-Based Extraction and Recovery Method for Almond (<Emphasis Type="Italic">Prunus armeniaca L</Emphasis>.) Protein

A novel method for protein extraction from sweet almonds with aqueous polyethylene glycol (PEG) as solvent and recovery from the extraction solution was developed. The extraction yields of different solvents, such as sodium hydroxide, sodium chloride, PEG 200, PEG 400, and PEG 600 aqueous solutions, were investigated and PEG 200 showed the highest extraction efficiency. The PEG-based microwave-assisted extraction (MAE) parameters were then optimized using response surface methodology. Under optimum condition, PEG 200 concentration of 25 % (w/w), liquid to solid ratio of 22 mL g^?1, microwave power of 120 W, extraction temperature of 45 °C, and extraction time of 4 min, the average extraction yield was 93.75?±?3.15 %. Subsequently, the almond protein was recovered from the extraction solution containing PEG with an isoelectric point-ethanol synergy precipitation protocol. The combined technique integrated the speed of isoelectric point precipitation with the completeness of alcohol precipitation. The recovery of almond protein was 98.81 % with a time of 3–5 min. The proposed PEG-based MAE and synergy precipitation protocol provide a rapid and effective method for almond protein extraction and recovery and have the potential to be used for other plant proteins.     

Extraction of protein from expeller- and solvent-extracted coconut meal by dilute acid,alkali, and salt solutions

The extractability of protein (nitrogen) from poonac (the press-cake left after extraction of oil from dried coconut kernel) with dilute aqueous hydrochloric acid, sodium hydroxide, and salt solutions has been investigated. Experiments were carried out on both expeller poonac and solvent-extracted poonac, the protein of the former being more soluble. Approximately 40% and 55% of the poonac protein nitrogen was extractable with 0.15% aqueous acid and alkali, respectively, under optimum conditions. Dilute salt solutions were found to have a comparatively poor solubilising effect under the conditions employed. Increasing the fat content of expeller poonac to 10% increased the nitrogen extracted by acid but not by alkali solutions.     

Techniques for Extraction of Brewer’s Spent Grain Polyphenols: a Review

Million tons of brewer’s spent grain (BSG) are annually produced worldwide as brewing industry by-products. BSG represents a valuable source of phenolic compounds, which have attracted much attention due to their diverse health benefits. Relevant strategies have been developed for their efficient extraction, in order to commercially exploit these resources. This review focuses on the current extraction methods used to obtain phenolic compounds from BSG, ranging from more traditional to advanced techniques. The commonly used methods are the conventional solid–liquid extractions, employing organic solvents, alkaline, and enzymatic reactions. However, the inherent difficulties in screening and obtaining these compounds have led to the development of advanced extraction techniques. Pressurized fluid extraction, supercritical extractions, and microwave-assisted and ultrasound-assisted extractions are some of the novel extraction techniques that have been recently explored. These techniques have been mostly applied for phenolic recovery from barley and malt, as well as other types of cereals. In this review, it is shown that these novel techniques may provide an innovative approach to extract phenolics from BSG or related products, following an in-depth discussion on the major strengths and weaknesses identified in each technique.     

Kinetics and equilibria of tea infusion: Part 8—the effects of salts and of pH on the rate of extraction of theaflavins from black tea leaf

The rates of extraction of theaflavins from sieved Kapchorua Pekoe Fannings (600–710 μm) and from a Ceylon Broken Orange Pekoe Fine Leaf Blend have been measured at 80°C with a set of aqueous salt and buffer solutions spanning the pH range 3·1 to 8·1. There was little effect on adding 1:1 electrolytes but considerable decreases in rate occurred in the presence of calcium chloride. The rate constants in acid buffers were the same as in a normal unbuffered infusion but in alkaline buffers of pH 8 they were over 50% larger. This phenomenon was quantitatively accounted for by the partial dissociation of theaflavins at higher pH and the greater diffusion coefficient of the resulting ionic salt. The relevance of these findings to tea brewing and to industrial theaflavins extraction is discussed.     

Endogenous amino acid flow at the terminal ileum of the rat determined under conditions of peptide alimentation

The study aimed to determine endogenous ileal amino acid excretion in the growing rat fed an enzymically hydrolysed casein (EHC) based diet with subsequent treatment of the digesta using ultrafiltration technology. Comparison was made with endogenous excretions obtained from rats fed an EHC-based or a protein-free diet and without any treatment of the ileal digesta. Preliminary investigations were made to determine the filtration efficiency of the ultrafiltration devices and to examine three alternative prefiltration treatments, trichloroacetic acid (TCA) and perchloric acid (PCA) precipitation, and centrifugation (SPIN). In the preliminary work, 15 purified protein, peptide and amino acid solutions were ultrafiltered using a molecular weight (MW) exclusion limit of 10000 Da, and the recovery of nitrogen indicated an effective filtration (generally >90% separation) on nominal molecular weight. Further, fresh rat ileal digesta samples were treated with either TCA, PCA or SPIN. The resulting supernates were ultrafiltered and the fractions were analysed for nitrogen and amino acids. The precipitates contained 23, 57 and 41% of the total nitrogenous material for the TCA, PCA and SPIN treatments, respectively, indicating that PCA was the most effective precipitant. In the main study, twelve 100-g male rats were fed either an EHC-based diet or a protein-free diet, and samples of ileal digesta were collected after slaughter. The digesta from the six EHC-fed rats were ultrafiltered after centrifugation, and the high molecular weight fraction was added to the precipitate. Endogenous ileal amino acid flows were determined for the total digesta and for the digesta following the centrifugation plus ultrafiltration treatment. The endogenous amino acid flows were generally higher for the total digesta than for the digesta following centrifugation plus ultrafiltration and significantly so (P<0.05) for lysine, glutamin acid and proline. The protein-free fed rats had significantly P<0·05) lower amino acid flows than those rats fed the EHC-based diedt (ultrafiltration treatment), the greatest differences occurring for isoleucine, serine, glutamic acid, valine, leucine, alanine and threonine.     

双酶法制备富含多酚的荞麦浓缩蛋白及体外消化研究

开发一种双酶结合膜分离的方法制备富含多酚的荞麦浓缩蛋白,系统比较了双酶法与传统碱溶酸沉法、盐提法在蛋白质及多酚的含量和回收率、溶解性等方面的差异;并结合SDS-PAGE、氮释放量、胶束多酚释放量等,考察了荞麦浓缩蛋白的模拟体外消化。结果表明:相对于碱溶酸沉法和盐提法,双酶法制备荞麦蛋白不仅具有较高的蛋白质质量分数(49.07%)和最高的蛋白回收率(57.93%),而且多酚质量分数(11.35%)显著高于碱溶酸沉法(3.65%)和盐提法(2.67%),回收率更高达70.89%,多酚多以结合态与蛋白共存;体外消化试验后,3种残渣蛋白SDS-PAGE分析结果相似,分子质量大于14.4 ku的组分全部裂解;此外,双酶法制备的荞麦蛋白氮释放量相对较低(43.30%),而胶束的多酚释放量高达2.05%,是良好的抗消化蛋白。     

Alkaline Extraction of Protein from Spent Honey Bees

Adult honey bees killed after honey harvest were analyzed and evaluated as a raw material for protein extraction. Bees collected were 49.8% crude protein, 7.54% total lipid, and 27.1% reducing sugar (moisture-free basis). Whole bees were homogenized, body proteins solubilized in alkali, chitin removed by filtration, and protein recovered by acid precipitation. Amount of protein solubilized by NaOH addition varied from negligible without alkali (pH 6.1) to 93% of body crude protein with severest treatment at pH 11.2. With alkali extraction at pH 10.5 and acid precipitation at pH 5.5, 59% of total solids were found in the precipitate and 41% remained in the supernatant. The precipitate was 66.3% crude protein, 9.4% total lipid and 7.9% ash. Heads, thoraces and abdomens were separated and each separately extracted (pH 10.5) and precipitated (pH 5.5). Amino acid analyses of heads (70.1% protein), thoraces (54.9% protein) and abdomens (36.6% protein) permitted evaluation of protein quality. Thorax protein was most homogeneous for amino acids analyzed, and all were nutritionally limited by sulfur containing amino acids.     

Herstellung und Charakterisierung von eiweißarmem zellstrukturiertem Material

Materials with cellular structure and a low protein content but a high pectin content have been prepared from apple parenchyma by simple procedures with only a few steps using small amounts of solvents. Materials with cellular structure from apple and a protein content less than 4% and a water-binding capacity higher than 80 g/g were obtained from the pressing residues of apple parenchyma by extraction at pH 8,4 to 9,1 and temperatures from 30 to 40° C, blanching in an aqueous environment, dehydration by ethanol and careful final thermal drying. Futhermore, additonal steps of alkaline deesterification and washing with acid were carried out for the preparation of samples with a low degree of esterification of the pectin component and a small content of ash. Such materials have a high content of free carboxyl groups (more than 1 mmol/g), but a reduced water-binding capacity.     

Biovalorization of brewers’ spent grain for the production of laccase and polyphenols

Brewers’ spent grain (BSG) is the main solid by‐product of the brewing process and is typically disposed of as cattle feed. In this study, BSG was evaluated as a substrate for the production of polyphenols and the lignin‐degrading enzyme laccase using fungal solid‐state fermentation by Trametes versicolor. Laccases are finding increasing applications in the food industry and polyphenols have benefits for human health. After 14 days of fermentation with T. versicolor, there was a 3.4‐fold increase in the extraction of total polyphenols compared with untreated BSG. Using BSG as the sole source of carbon and nitrogen, maximum laccase activity was achieved after seven days of treatment with an activity of 560 U/L. Based on these results, BSG is suggested to be a good lignocellulose waste material to produce value‐added products such as the enzyme laccase and polyphenols. Copyright © 2018 The Institute of Brewing & Distilling     

Investigation of Faba Bean Protein Recovery and Application to Pilot Scale Processing

Extraction and precipitation conditions were assessed for recovery of protein from dehulled faba bean flour on a laboratory scale. 10°C versus 20°C extraction did not affect solubility of nitrogenous components. However, more were extracted at pH 9 or 10 than at pH 7. Tap water extracted slightly more nitrogenous materials than 0.3M sodium chloride. Study of pH 4.0 to 5.3 for protein precipitation showed a higher yield of protein was obtained at lower pH. However, apparently simultaneous precipitation of nonproteinaceous material caused overall lower protein composition of the isolates from lower pH. Pilot scale processing of dehulled faba bean flour produced an isolate which was 92.5% protein, and represented a yield of 48% of the original protein.     

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 Six Sample Preparation Methods for Analysis of Food Additives in Milk Powder

Milk powder matrix is highly complex with significant amounts of lipids and proteins; thus, the determination of trace residues and contaminants in it often requires extensive sample extraction and preparation prior to instrumental analysis. An ideal preparation method is simple, less time consuming, and relatively inexpensive. It enhances the recovery and involves low consumption of toxic organic solvents. In this study, six sample preparation methods for milk powder were established and compared, including liquid–liquid extraction, organic precipitation, heavy precipitation, and three different solid-phase extraction (SPE) methods. The extraction recovery was evaluated by determination of six preservatives and sweeteners (benzoic acid, sorbic acid, natamycin, lysozyme, saccharin sodium, and aspartame) by HPLC-DAD in whole and skimmed milk powder samples. The results showed that the reproducibility of liquid–liquid extraction was not as high as the SPE method although the recovery was beyond 80 %; the organic precipitation and heavy precipitation gave poor recovery (below 20 %) of lysozyme; the highest recovery (>85 %) was achieved using the HLB cartridge compared to C18 and MAX cartridges. Therefore, the HLB cartridge was selected as the most appropriate sample preparation material for the determination of the six preservatives and sweeteners in milk powder samples by HPLC-DAD.     

Identification of kafirin film casting solvents

The sorghum prolamin protein, kafirin can be used for making edible films. Several food compatible solvents were examined to identify novel kafirin film casting solvents to replace aqueous ethanol, commonly used for prolamin film casting. Glacial acetic acid and lactic acid were identified as the best primary solvents and 55% (w/w) aqueous isopropanol as a good binary solvent. However, the low volatility of the latter two prevents their use as casting solvents. Films could be cast from glacial acetic acid at 25 °C, a much lower temperature than the 70 °C required with aqueous ethanol. The sensory, tensile, and water barrier properties of the films cast from glacial acetic acid at 25 °C and aqueous ethanol at 70 °C were almost the same. However, the use of glacial acetic acid at 25 °C for casting kafirin films is advantageous as it gave films of more consistent quality.     

Protein and gossypol extractability from cottonseed flour

The extractability of protein and free-gossypol from fully gossypolised cottonseed flour was investigated. The various parameters studied include (i) effect of pH (ii) effect of salts and (iii) the combined effect of pH and salts. The results indicated that it is possible to obtain a protein isolate free from free-gossypol by alkaline extraction at pH values of 9 and 10. Highest protein extraction (57%), highest protein recovery (96%) and highest protein content of the precipitate (75%) occurred at pH 10. In general, dilute aqueous electrolytes did not accomplish significantly higher extracta-bilities although they resulted in comparatively lower free-gossypol contents in the protein precipitate. However, with 1.0m CaCl2 protein extraction was 75% but both protein recovery (61%) and the protein content of the precipitate (61%) was comparatively low. Extraction in the presence of salts and alkali did not improve protein extractability and gave a protein isolate high in free-gossypol content.     

The extraction of beef bones with water, dilute sodium hydroxide and dilute potassium chloride

To investigate the recovery of waste meat on bones, crushed beef bones were extracted under various conditions within a temperature range of 50 to 125 ºC and a pH range of 6.3 to 11.6. The extracts were analysed for total solids, collagen, non-collagen protein, non-protein nitrogen, creatinine and ash. The water extraction of collagen increased and of non-collagen protein decreased with increases in temperature up to 100 ºC and the total yield of protein markedly increased with alkaline pH.     

Recovery of proteins from beef bone and the functionality of these proteins in sausage batters

Four solutions [4% sodium chloride (control), 4% sodium chloride with 0.3% sodium tripolyphosphate (STP), 0.3% tetrasodium pyrophosphate (TTP) or 0.05 M sodium hydroxide (NaOH)] were used to extract proteins from beef bones. Three bone solution ratios (1:1, 1:4 or 1:10), three bone types [vertebra (lumbar), rib (4-7) and leg (femur)] and two methods of protein recovery from the extraction slurries [dialysis against 0.03 M potassium phosphate buffer (pH 5.3) and acid precipitation] were evaluated. Solutions containing phosphates or NaOH were more effective in extracting protein than sodium chloride alone. Total protein recovery was highest from vertebra bones while extraction of proteins from leg bones resulted in the lowest recovery. A solution to bone ratio of 1 to 10 recovered more total protein from vertebra or rib bones than leg bones. Dialysis recovered more total protein from extraction solutions when the protein concentration was low. Acid precipitation, however, worked best if the protein concentration in the extraction solution was high. Extraction procedures resulted in some myosin degradation. Proteins extracted from beef bone materials and recovered by dialysis, performed equally as well as other commercially available proteins when added to a finely comminuted sausage product.     

Impact of pulsed electric field pre-treatment on nutritional and polyphenolic contents and bioactivities of light and dark brewer's spent grains

Pulsed electric field (PEF) pre-treatment, at 2.8 kV/cm with 3000 pulses of 20 μs pulse-width, was applied on brewer's spent grains (BSG) followed by aqueous extraction at 55 °C, 220 rpm for 16 h. PEF pre-treatment showed significantly increased yields (p < 0.05) of carbohydrate, protein, starch and reducing sugar in extracts from dark BSG compared to untreated samples. Light BSG extracts had significantly higher (p < 0.05) levels of free d-glucose and total free amino acids (18.5–33.3 and 21–25 mg/g dry weight extract (Dwe)), compared to dark extracts (5 and 1.2 mg/g Dwe respectively). Dark BSG extracts showed significantly higher (p < 0.05) total phenolics (3.97–4.88 mg GAE/g Dwe) compared to light BSG extracts (0.83–1.40 mg GAE/g Dwe). Furthermore, PEF treated light BSG showed higher antimicrobial activity with minimum inhibition concentration (MIC) of 50 and 25 mg/mL against Salmonella typhimurium and Listeria monocytogenes, respectively compared to the untreated extracts (>50 mg/mL) with lowest MIC value of 1.56 mg/mL against Staphylococcus aureus. All the BSG extracts induced the release of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and chemokines (IL-8, MCP-1 and MIP-1α) confirming immunomodulatory activity.