Soluble Hydrolysate Research Articles

Subcritical water hydrolysis of chia seed proteins and their functional characteristics

Deoiled chia flour is an important protein-rich by-product of the chia oil industry. This work used green process subcritical water hydrolysis to hydrolyse chia seed protein from deoiled chia flour and compared it with alkali hydrolysis. The yields of total protein, total amino acids, and reducing sugars in the soluble hydrolysate products were examined in relation to the effects of the extraction conditions (reaction time and temperature). Hydrolysates generated at 225 °C after 30 min of hydrolysis exhibited the highest protein content (213.76 ± 0.44 mg/g of chia protein concentrate) and total free amino acid content (44.26 ± 0.79 mg/g of chia protein concentrate), while the highest extent of extraction (62.72 ± 1%), and degree of hydrolysis (13.85 ± 0.50%) was observed at 200 °C after 30 min of hydrolysis. Alkali hydrolysis exhibited significantly (p < 0.05) lower protein hydrolysis (10.66 ± 0.51%) and total free amino acids (22.66 ± 0.53 mg/g of CPC) than subcritical water hydrolysis. SEM, elemental analysis and XRD conferred the degradation of CPC and provided strong evidence in supporting subcritical water hydrolysis for chia seeds. Subcritical water hydrolysates can be envisioned to develop functional foods from chia seeds.

Steering the formation of cellobiose and oligosaccharides during enzymatic hydrolysis of asparagus fibre

The enzymatic conversion of cellulosic-rich waste streams of white asparagus into cellobiose and cello-oligosaccharides (COS) is proposed for producing a natural carrier agent. The enzyme cocktail ‘Celluclast’ was used to steer towards maximum conversion and minimum formation of monosaccharides to obtain an enzymatic hydrolysate with a high glass transition temperature (Tg). Different enzyme loadings and hydrolysis times were tested in combination with a sodium hydroxide pre-treatment of the asparagus fibre. A loading of 700 nkat/g substrate and 7 h of hydrolysis time resulted in the best yield/purity combination, namely a conversion of 36 g/100 g cellulose with 81% celllobiose/COS. The same hydrolysis conditions were tested in a larger bench-scale experiment (conversion of 45 g/100 g cellulose) and the soluble hydrolysates were concentrated and spray-dried. The high Tg (108 °C) of the spray-dried hydrolysates of asparagus fibre proves its potential usage as a carrier agent for spray drying.

Bioprospecting microwave-alkaline hydrolysate cocktail of defatted soybean meal and jackfruit peel biomass as carrier additive of molasses-alginate-bead biofertilizer

The extraction of soluble hydrolysate protein and sugar from a biomass cocktail of defatted soybean meal (DSM) and jackfruit peel (JP) was examined using microwave-alkaline hydrolysis by varying the NaOH concentrations (0.04–0.11 M) and residence times (2–11 min). Based on the central composite design, the optimized parameters were achieved at 0.084 M NaOH concentration (100 mL), for 8.7 min at 300 W microwave power level to obtain the highest protein (5.31 mg/mL) and sugar concentrations (8.07 mg/mL) with > 75% recovery. Both raw and detoxified hydrolysate (using activated carbon) were correspondingly biocompatible with Enterobacter hormaechei strain 40a (P > 0.05) resulting in maximal cell counts of > 10 log CFU/mL. The optimized hydrolysate was prepared as an additive in molasses-alginate bead encapsulation of strain 40a. Further evaluation on phosphate and potassium solubilization performance of the encapsulated strain 40a exhibited comparable results with those of free cell counterpart (P > 0.05). The DSM-JP hydrolysate cocktail holds potential as a carrier additive of encapsulated-cell bead biofertilizers in order to sustain bacterial cell quality and consequently improve crop growth and productivity.

A Rational Approach for the Production of Highly Soluble and Functional Sunflower Protein Hydrolysates.

Exploitation of plant proteins as an alternative to animal proteins currently presents an important challenge for food industries. In this contribution, total sunflower protein isolate from cold press meal was used as a starting material for the generation of highly soluble and functional hydrolysates that could be used in various food formulations. To do this, a rational and complete approach of controlled hydrolysis was implemented using the individual Alcalase and Prolyve enzymes. The method of stopping the hydrolysis reaction was also evaluated. The influence of operating conditions on hydrolysis kinetics and enzymatic mechanism was studied to identify the appropriate hydrolysis conditions. The gain of the solubility was then analyzed and compared to that of the initial proteins. Finally, the emulsifying and foaming properties (capacities and stabilities) of the resulting hydrolysates were also assessed. As a result, controlled enzymatic proteolysis significantly improved the sunflower protein solubility at neutral pH (twofold increase) and generated highly soluble hydrolysates. The limited proteolysis also maintained the good foam capacities and allowed an improvement in the initial foam stabilities and emulsifying capacities and stabilities of sunflower proteins. This contribution can greatly increase the value of sunflower meal and help in the development of sunflower protein products in the future.

Anaerobic enrichment of &lt;i&gt;Bacillus&lt;/i&gt; alkylbenzene remedial consortia from waste biomass melanoid sources

&lt;abstract&gt; &lt;p&gt;Bioremediation of alkylbenzenes, including toluene, ethylbenzene and xylenes, was performed using fermentable aromatic sources and electron mediators by &lt;italic&gt;Bacillus cereus&lt;/italic&gt; 301 in a limited oxygen state. The fermentation of small fermentable aromatic melanoids from cow manure as soluble humus hydrolysates or sugarcane molasses as saccharine, glucose and limited basal medium was compared. Thus, an evaluation model of exponential decline against a control was incorporated for interpretation of remedial data. The significance of the present strategy for constructing multivariant effects of electron donors could be objectively judged by pattern comparison with the short-term data analyzed. Thus, grafted aromatics as methyl- or ethylbenzene require much more microbial reaction time, even with mixed aromatic donors or stronger electron donors such as methanol in the original reduced medium, as indicated in the scatter chart. However, completion of the remedial time was needed by the kinetic simulation, and even low, smooth data were expressed. Among the exponential decay curves indicated, the carbon sources in the mix were favorably expressed. The smooth pattern indicated that fermentations with glucose and molasses showed lower remedial activity than melanoids or the indole series. The vigor increase was better for melanoid carbon in the initial fermentation of 24 h, while molasses increased later at 72 h and was more quenched by amending indole acetic acid (IAA) or indole expression. The molecular interaction of the electron mediator indole acetic acid in most trials indicated a quenched effect on toluene and ethylbenzene degradation, even when mixed with the original reducing medium, but expressed better with molasses in both kinetic simulations and growth effects. Thus, combining electron mediators such as IAA for &lt;italic&gt;Bacillus&lt;/italic&gt; may offer a new degradation route for the metabolite alkylbenzene, which is worth further exploration for environmental aromatic waste remediation and combined restoration strategies.&lt;/p&gt; &lt;/abstract&gt;

Plant response to biowaste soluble hydrolysates in hibiscus grown under limiting nutrient availability

ABSTRACTBiostimulants are substances promoting plant growth, quality and stress resistance. The present work aimed to investigate whether soluble hydrolysates from biowaste performed as biostimulants. Hibiscus (Hibiscus moscheutos L. subsp. palustris) plants were subjected to four treatments: standard fertilization, low fertilization (LF), and LF with added soluble digestate or soluble compost. Plant performance indicators were biomass accumulation, biometric parameters, leaf gaseous exchanges and elemental composition, and nitrogen (N)-use efficiency. LF negatively affected most of the investigated parameters. However, plants treated with biowaste-derived products performed better than untreated low-fertilized plants (+21 to 145% for biomass accumulation and biometric parameters, and carbon assimilation rate) and for many parameters reached values comparable to those showed by standard-fertilized plants or even higher, as in the case of Potassium (K), Silicon (Si), and Molybdenum (Mo) leaf content, and N use efficiency. Therefore, the tested soluble hydrolysates demonstrated to have biostimulant properties in hibiscus grown under nutritional stress.

Fração solúvel de hidrolisado proteico de sardinha na alimentação do jundiá

O objetivo deste trabalho foi avaliar o efeito da inclusão da fração solúvel do hidrolisado proteico de sardinha sobre a estabilidade das dietas e a excreção de amônia de juvenis de jundiá. Foram elaboradas sete dietas experimentais com as frações solúveis dos hidrolisados de músculo e ví­­sceras de sardinha. A determinação da estabilidade do pellet na água foi medida em intervalos de tempo diferentes (5 min, 10 min, 20 min, 30 min, 1 h e 1,5 h). A determinação de amônia total foi realizada a cada cinco horas. Como resultado do teste de estabilidade foi detectado diferença significativa somente no perí­­odo de 5 minutos, onde a dieta contendo 20% de hidrolisado solúvel de musculo teve maior taxa de lixiviação em comparação com a dieta controle. A partir de 10 horas de observação, a concentração de amônia foi maior no controle em relação aos outros tratamentos. O hidrolisado proteico de resí­­duo de sardinha tem grande potencial para ser utilizado nas rações do jundiá, melhorando a eficiência ambiental das dietas. A inclusão de até 10% da fração solúvel de hidrolisados de músculo e de ví­­sceras de sardinha não afeta a estabilidade das dietas, além de diminuir a excreção de amônia.

Novel angiotensin-converting enzyme inhibitory peptides from caseins and whey proteins of goat milk

Angiotensin-converting enzyme (ACE) plays a central role in blood pressure regulation by producing the vasoconstrictor angiotensin II. The inhibition of ACE with natural inhibitors, as alternatives to avoid the side effect of synthetic drugs, is a major target in the prevention of hypertension. In this study, we examined the separated caseins and whey proteins of goat milk for the presence of ACE inhibitory peptides. Digestion of isolated whey proteins and caseins of goat milk by gastric pepsin generated soluble hydrolysates exhibiting significant inhibition of ACE compared to weak inhibition by undigested proteins. The hydrolysates were fractionated by size exclusion chromatography, Sephacryl S-100 column, into four fractions (F1–F4). The late-eluting fraction (F4) of either whey or caseins exhibited greater ACE inhibition. Peptides in both F4 fractions, isolated by RP-HPLC, exhibited variable ACE inhibitory activities with the hydrophobic peptide peaks being the most potent ACE inhibitors. MALDI-TOF MS/MS resulted in identification of three potent ACE inhibitory peptides: PEQSLACQCL from β-lactoglobulin (residues 113–122), QSLVYPFTGPI from β-casein (residues 56–66), and ARHPHPHLSFM from κ-casein (residues 96–106). The peptides from whey and caseins exert significant ACE inhibitory activities comparable to that of captopril, an antihypertensive drug, exhibiting IC50 values of 4.45μM and 4.27μM, respectively. The results introduce, for the first time, new potent ACE-inhibitory peptides that can be released by gastric pepsin of goat milk whey and caseins and thus may pave the way for their candidacy as anti-hypertensive bioactive peptides and prevention of associated disorders.

Effect of diets containing different types of sardine waste (Sardinella sp.) protein hydrolysate on the performance and intestinal morphometry of silver catfish juveniles (Rhamdia quelen)

In this study two fractions of muscle hydrolysate were tested, soluble and insoluble (FSM and FIM), they were assessed individually and combined with each other (FSM+FIM). Also, two fractions of hydrolyzed viscera: soluble of natural and industrialized viscera (FSVN and FSVI) were tested on the performance and on the intestinal morphology of juvenile catfish ( Rhamdia quelen ). The experimental design was completely randomized with five treatments and five replicates. Juveniles were kept in aquariums with density of eight fish per tank and were cultured for 56 days. The results were analyzed using parametric variance analysis (ANOVA) and subjected to the Duncan test (5% significance level). The best results on final weight, weight gain, feed conversion rate, and protein efficiency ratio were obtained with the diet containing FSM+FIM, and the diet containing the FSVI. The latter was also the most consumed by the animals. The diet containing FIM was the one that provided the worst consumption results. The worst feed conversion rate was obtained for the diet containing FSM. Survival and body composition did not differ between treatments. The separation of the soluble and insoluble fractions is not necessary or even recommended when the goal is to use the muscle hydrolysate as the ingredient in feed for silver catfish juveniles. The best performance results obtained were with the combination of soluble and insoluble fractions of muscle hydrolysate, and with the industrial viscera soluble hydrolysate. The degree of hydrolysis has a direct effect on feed consumption.

Application of municipal biowaste derived products in Hibiscus cultivation: Effect on leaf gaseous exchange activity, and plant biomass accumulation and quality

Two urban biowaste materials, fermented under anaerobic and aerobic conditions, their soluble and insoluble alkaline hydrolysates, and a commercial biostimulant product, were compared for their capacity to boost Hibiscus crop production and quality. Plants were grown in 4‐litre pots, containing peat and pumice as substrate, under optimal growing conditions. A randomized-block experimental design was adopted. Two types (main factors of variability) of treatments were applied, i.e. by blending the above products with the substrate at transplant, and by fertigation using the soluble hydrolysates only. Plant biomass characteristics and ecophysiological parameters were measured. Mean effect of factors and their interactions were assessed by two‐way ANOVA. Principal component analysis was performed by using the different dependent variables to summarize the most relevant differences among treatments. Compared with the control (untreated plants), the applied treatments enhanced most of the investigated parameters. The most valuable effects were observed for total biomass accumulation (+25%), plant height (+10%), leaf chlorophyll SPAD index (+15%) and net photosynthesis (+24%). The hydrolysates performed better than the pristine materials. The former ones were comparable to the commercial biostimulant. The results confirmed the hypothesis that biowaste derived products induce biostimulant activity on Hibiscus; their application can improve cultivation sustainability.

Production and characterisation of alcohol-insoluble dietary fibre as a potential sourcefor functional carbohydrates produced by enzymatic depolymerisation of buckwheat hulls

We examined the potential use of buckwheat hulls as a raw material for producing soluble dietary fibre. The insoluble fibre fraction obtained from buckwheat hulls was hydrolysed by two commercial enzymes (Celluclast 1.5L for the cellulose fraction and Viscozyme L for the hemicellulose fraction) to obtain soluble fibre hydrolysates. Alcohol-insoluble dietary fibre (AIF) was separated from the freeze-dried soluble hydrolysate by treatment with 85% ethanol. The water-holding, oil-binding, and swelling capacities of AIF were increased by enzymatic hydrolysis. AIF had significantly (P&amp;nbsp;&amp;lt; 0.05) higher functional properties than the control. AIF from the hemicellulose fraction effectively hindered the diffusion of glucose and bile acid from dialysis membranes, and had a significantly (P &amp;lt; 0.05) greater bile acid inhibitory effect than carboxymethylcellulose or pectin. It can be concluded that AIF from buckwheat hulls by enzymatic hydrolysis can used as dietary supplement and additive in the food industry.

Characterisation of hydrolysates prepared from engraved catfish (Nemapteryx caelata) roe by serial hydrolysis.

Protein hydrolysates were prepared from defatted engraved catfish roe using alcalase enzyme by a two-stage serial hydrolysis process. The soluble hydrolysate formed after first stage of hydrolysis was removed (RH-1) and fresh enzyme was added at the same concentration to achieve further hydrolysis (RH-2). Further, compositional, surface-active and antioxidant properties of both hydrolysates were compared. The SDS-PAGE profile showed two distinct bands for RH-1, whereas no bands were visible for RH-2. On the other hand, gel filtration chromatography of the hydrolysates indicated 3-4 distinct fractions. Both the hydrolysates showed similar foam forming abilities, however, RH-1 exhibited poor foam stability. Emulsion properties of RH-1 were superior to that of RH-2. The major fractions eluted through gel filtration column were screened for antioxidant properties. Higher DPPH radical scavenging and metal chelating properties were observed for RH-1second fragment, whereas FRAP and Fe(2+) reducing power was highest for second fragment of RH-2.

Influence of Different Hydrolysis Processes by Trypsin on the Physicochemical, Antioxidant, and Functional Properties of Collagen Hydrolysates from Sphyrna lewini, Dasyatis akjei, and Raja porosa

ABSTRACTAcid soluble collagen hydrolysates from the cartilages of Sphyrna lewini, Dasyatis akjei, and Raja porosa on different hydrolysis conditions by trypsin were prepared and named as S, D, and R, respectively. The hydrolysates (S1, D1, and R1) obtained from hydrolysis in pH 2.5, 3 h, 37°C presented wonderful foaming and emulsifying capacities, caused by their high average molecular weights (AMWs), high degree of Pro and Lys hydroxylation, and imino acid contents (17.1, 15.3, and 14.1%). At the concentration of 0.1% (w/v), the foaming capacities of S1, D1, and R1 were 104.75 ± 2.57, 63.87 ± 2.73, and 76.87 ± 2.02%; and the emulsifying activity indexes of them were 116.07 ± 1.89, 91.04 ± 1.79, and 123.85 ± 2.14 m2/g, respectively. Conversely, hydrolysates (S2, D2, and R2) obtained from hydrolysis in pH 7.8, 3 min, 37°C exhibited strong scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (EC50 0.568, 0.680, and 1.634 mg/mL), hydroxyl radical (EC50 0.253, 0.376, and 0.438 mg/mL), and moderate reducing power (0.0465–0.4702 at the concentration of 5 mg/mL), due to their low AMWs. The results indicated that S1, D1, and R1 could be used as emulsifiers and foaming agents, and S2, D2, and R2 could be used as natural antioxidants in food systems.

Fertilization of bean plants with tomato plants hydrolysates. Effect on biomass production, chlorophyll content and N assimilation

Humic-like substances obtained by alkaline hydrolysis of composted organic wastes are known to improve plant productivity. Little is known concerning the effect on plant growth of hydrolysates obtained by alkaline treatment of non-composted vegetal residues.The aim of this study was to prepare, characterize, and apply in horticulture the soluble and the insoluble fractions obtained by alkaline hydrolysis of exhausted tomato plants. The hydrolysates were prepared in a pilot plant from the tomato plants residue in powder form and characterized by solid state 13C NMR spectrometry, elemental analysis and potentiometric titration. The characterization of the soluble hydrolysate gave evidence of lignin and hemicellulose moieties, together with protein, peptide or amino acids while most of the cellulose was found in the insoluble fraction. Plant beans were grown on a peat and sand substrate fertilized with low application rate of the tomato plant powder and of the corresponding hydrolysates. The effect on bean plants was assessed by determination of plant growth, chlorophyll content, nitrate reductase, glutamine synthetase, glutamate synthase activities and soluble proteins.The tomato plant powder had no effect on all parameters measured on the grown bean plants. On the contrary, the insoluble and soluble substances sourced by alkaline hydrolysis of the tomato plant powder exhibit strong effects, mainly the increase of nitrogen assimilation typical of biostimulants.The results suggest that residual plant biomasses are source of efficient biostimolant and propose the hydrolysis of residual biomass as a viable profitable process to contribute important improvements also for waste management practices.

Functional and Antioxidant Properties of Angelwing Clam (Phplas orientalis) Hydrolysate Produced using Alcalase

In this study, Hydrolysate from angelwing clam (Pholas orientalis) was produced at 0, 1, 2 and 3 hrs and E/S ratio of0.5 and 3%using alcalase where the pH and temperature were kept constant at pH 8.5 and 60°C, respectively. The hydrolysates were analysed for antioxidant and functional properties such as solubility, emulsifying properties and water and oil holding capacity. Degree of hydrolysis (DH), yield, functional and antioxidant properties were influenced by the hydrolysis time and E/S ratio. Higher enzyme concentration (E/S 3%) and longer hydrolysis time increased the DH. Yield was higher at E/S 3% but reduced with hydrolysis time. Longer hydrolysis time produced more soluble hydrolysate and higher metal chelating activity but lower in emulsifying properties and DPPH activity. Higher enzyme concentration resulted in increase only in solubility and metal chelating activity. This study revealed that enzymatic hydrolysis using alcalase should be performed at shorter hydrolysis time using intermediate concentration of enzyme (E/S between 0.5 to 3%) in order to produce angelwing clam hydrolysate with collectively good functional and antioxidant properties.

Functional and Antioxidant Properties of Angelwing Clam (Pholas orientalis) Hydrolysate Produced using Alcalase

In this study, hydrolysate from angelwing clam (Pholas orientalis) was produced at 0, 1, 2 and 3 hrs and E/S ratio of 0.5 and 3% using alcalase where the pH and temperature were kept constant at pH 8.5 and 60°C, respectively. The hydrolysates were analysed for antioxidant and functional properties such as solubility, emulsifying properties and water and oil holding capacity. Degree of hydrolysis (DH), yield, functional and antioxidant properties were influenced by the hydrolysis time and E/S ratio. Higher enzyme concentration (E/S 3%) and longer hydrolysis time increased the DH. Yield was higher at E/S 3% but reduced with hydrolysis time. Longer hydrolysis time produced more soluble hydrolysate and higher metal chelating activity but lower in emulsifying properties and DPPH activity. Higher enzyme concentration resulted in increase only in solubility and metal chelating activity. This study revealed that enzymatic hydrolysis using alcalase should be performed at shorter hydrolysis time using intermediate concentration of enzyme (E/S between 0.5 to 3%) in order to produce angelwing clam hydrolysate with collectively good functional and antioxidant properties.

Optimization of micro-aeration intensity in acidogenic reactor of a two-phase anaerobic digester treating food waste

Micro-aeration is known to promote the activities of hydrolytic exo-enzymes and used as a strategy to improve the hydrolysis of particulate substrate. The effect of different micro-aeration rates, 0, 129, 258, and 387L-air/kg TS/d (denoted as LBR-AN, LBR-6h, LBR-3h and LBR-2h, respectively) on the solubilization of food waste was evaluated at 35°C in four leach bed reactors (LBR) coupled with methanogenic upflow anaerobic sludge blanket (UASB) reactor. Results indicate that the intensity of micro-aeration influenced the hydrolysis and methane yield. Adequate micro-aeration intensity in LBR-3h and LBR-2h significantly enhanced the carbohydrate and protein hydrolysis by 21–27% and 38–64% respectively. Due to the accelerated acidogenesis, more than 3-fold of acetic acid and butyric acid were produced in LBR-3h as compared to the anaerobic treatment LBR-AN resulting in the maximum methane yield of 0.27L CH4/g VSadded in the UASB. The performance of LBR-6h with inadequate aeration was similar to that of LBR-AN with a comparable hydrolysis degree. Nevertheless, higher aeration intensity in LBR-2h was also unfavorable for methane yield due to significant biomass generation and CO2 respiration of up to 18.5% and 32.8% of the total soluble hydrolysate, respectively. To conclude, appropriate micro-aeration rate can promote the hydrolysis of solid organic waste and methane yield without undesirable carbon loss and an aeration intensity of 258L-air/kg TS/d is recommended for acidogenic LBR treating food waste.

Hydrolysed Cellulose Material as Sulfate Reduction Electron Donor to Treat Metal- and Sulfate Containing Waste Water

The amenability of hydrolysed cellulose material to low cost sulfate reduction electron donor was examined with fluidized bed reactor (FBR) treating synthetic mine waste water. The studied cellulose material was dried Phalaris arundinacea reed, which was acid hydrolysed (1.5 w/w % H2SO4, 7 w/w % solids) at 120oC to hydrolyse polymeric materials to biodegradable monomers. The FBR was operated at 35oC, and ethanol has previously been used as the electron donor. FBR was fed with synthetic waste water (pH 4.5) containing soluble fraction of Phalaris arundinacea hydrolysate, metals (Fe and Zn) and sulfate. The switch of the electron donor from ethanol to hydrolysate was successful. The acidic influent was neutralized in the FBR by the alkalinity produced in the oxidation of Phalaris arundinacea hydrolysate. The main oxidation product of the soluble hydrolysate was acetate, which accumulated in the FBR during overloading. The percent sulfate reduction remained in the range of 40-95 %. The highest obtained hydrogen sulfide production was 0.91 g L-1d-1 at a hydraulic retention time (HRT) of 9 h, while highest sulfate reduction was 8.4 g L-1d-1 (HRT 8 h). Iron and zinc precipitated in the FBR, and highest metal precipitation rates were 1.14 g Fe L-1 d-1 and 30 mg Zn L-1d-1 (HRT 8 h). The electron donor load was measured as soluble chemical oxygen demand (CODs), and highest CODs removal rate was 2.13 g L-1d-1 (HRT 9 h) and CODs percent oxidation 92 % (HRT 10 h). Soluble Phalaris arundinacea hydrolysate was found to be a suitable electron donor for sulfate reducing FBR and mine waste water treatment. The soluble fraction of Phalaris arundinacea hydrolysate was used very efficiently by sulfate-reducing bacteria (SRB). Additionally, batch bottle assays showed that SRB-enrichment also used solid, dried Phalaris arundinacea as electron donor for sulfate reduction (total sulfide yield 340 mg L-1 in 14 days). The results of sulfate reduction and iron precipitation are shown in figures 1 A-B.

Solubilisation of cattle hide collagen by thermo-mechanical treatment

Widely insoluble collagen of skin was transformed into soluble hydrolysates by thermo-mechanical treatment in an internal mixer. During this treatment the fibrous structure of collagen disappeared. The degree of solubility depended on the duration of the treatment. Warm aqueous solutions of the hydrolysates were able to form stiff gels when cooled. However, the molecular weight distribution was totally different from that of gelatine. The increase of solubility showed that molecular weight decreases and that covalent bonds were cleaved. There were no hints that specific peptide bonds were cleaved more easily than others because the SEC showed no specific peaks. In contrast to gelatine manufacture, the thermo-mechanical treatment did not lead to a topochemical hydrolysis. This is one of the most important differences between gelatines and the samples which were produced by thermo-mechanical treatment. A second difference is the high content of very high molecular material in the samples.

Foaming and Emulsifying Properties of Fractions of Gluten Peptides Obtained by Limited Enzymatic Hydrolysis and Ultrafiltration

Gluten hydrolysates were prepared by limited enzymatic hydrolysis with a protease having a chymotryptic activity in the presence or in the absence of cysteine during the dispersion phase of the process. The hydrolysates were fractionated by ultrafiltration, using two inorganic membranes with different molecular weight cut-off (MWCO), 50 kg/mol and 150 kg/mol. The retentates were enriched in hydrophobic peptides and the permeates were enriched in hydrophilic peptides. The foaming and emulsifying properties of hydrolysates, retentates and permeates were analysed at two pHs (4 and 6·5) and two salt concentrations (0·2 and 2% NaCl). Hydrolysates displayed a foaming capacity, but the foams were not stable. Permeates generated foams at pH 6·5 only, and these foams had a very short life-time. Permeates displayed no emulsifying properties. Retentates yielded foams with a good stability and were more efficient than whole hydrolysates to stabilise emulsions. They provided a strong resistance to coalescence. The functional properties of retentates were only sightly influenced by pH and ionic strength. Neither cysteine addition, which helps gluten dispersion and increases the yield of soluble hydrolysate, nor the MWCO of the ultrafiltration membranes influenced the functionality of the hydrolysate fractions.