| The rapid increases in global population warrants the need for alternative sources of protein.Insects have,thus,been listed as potential resource;and one specie that could be beneficial in this regard is H.illucens(due to its rich protein content with extra benefits to the environment).The need to increase consumption globally is imperative as there is high demand on the already scarce protein sources available worldwide.Extracting the constituent protein/preparing protein hydrolysates from edible insects for novel/food applications is a promising approach to upsurge global consumption in the next 2-3 decades where humans are likely to rely on insect protein.The success of scale-up processing in this regards depend on process-limits or conditions for better yields,functionality and/or improved biological activity.Thus the functionality of such novel protein isolates need to be examined to ascertain their potential usage in food formulations.To obtain the protein isolates/hydrolysates,however,both conventional and novel(extraction and hydrolysis)technologies may be applied.The utilization of such technologies could impact the resultants(isolates,and hydrolysates)differently,which may consequently influence their functionality,biological activity and use in food formulations.Conventional(extraction and hydrolysis)processes,have been widely applied or found very useful in industry for many years.Novel technologies/processes such as ultrasonication(sonochemical action),however,has recently been documented as potentially useful in increasing product activity and extraction yield;while reducing enzyme consumption,production cost,and at same time ensuring end product quality.There are also,however,reports to suggest that ultrasonication may impair some functional traits of proteins.To this regards,this study focused on examining the impact of both conventional and ultrasonic processes on the extraction(alkaline-aided),functionality,and biological(in-vitro antioxidative)potential of protein preparations and hydrolysates from H.illucens larvae.The key contents and findings of the study are as follows:(1)Extraction of protein from larvae of H.illucens(HIL)for food applications was studied.Optimized procedure for conventional extraction of protein from HIL was investigated,and amino acid(AA)component,and physicochemical/functional properties(PFPs)of protein isolates were determine and compared.After,the influence of ultrasonication parameters on extraction yield was examined/screened.Box-Behnken's design with Box-Wilson methodology were applied in the optimization process.Following single-factor investigations,relational analysis indicated polynomial model could be used to illustrate influence of extraction parameters on protein yield.Response-surface plots showed extraction variables influenced(p<0.05)protein yield of HIL.The optimal extraction(optimal protocol–OP)conditions with highest yield(64.44%)were time-59.43 min,alkaline solution to sample ratio-24.85:1.00,and temperature-52.23°C.The protein extract obtained using the OP,compared to a modified protocol-MP(with conditions:60 min,15:1 alkaline solution to sample ratio,and 40°C)showed content of 80.42±0.90%and 76.91±0.91%respectively(p<0.05).The AA-scores were above that recommended by FAO.Variations existed between OP and MP extracts regarding PFPs,consistent with intrinsic fluorescence/AA-values.Influence of ultrasonication parameters on protein yield showed that,using sonication pretreatment conditions40±2 kHz,30 min,109 W/L,25:1(solvent to sample ratio),50°C,500ms,and pulse 15s on and 5s off could increase extraction yield by 20.31%.(2)The impact of ultrasonic(sonochemical)action and the reaction of edible insect protein(HILMP)as regards enzymolysis under varied enzyme concentration and temperature to explain the mechanism and effect of sonication on the reaction efficacy,molecular conformation,limits of kinetics and free-Gibbs energy,and antioxidative capacity were investigated.Control treatment was compared.The results showed that sonochemical-treatment enhanced HILMP-enzymolysis efficiency at various enzyme volume,and temperature.Enzymolysis-kinetics revealed sonochemical-treatment increased the rate constant(p<0.05)by 17.21,25.06,26.91,and 41.38%at 323,313,303,and 293 K respectively.On free-Gibbs,sonochemical-treatment reduced the reactants-reactivity energy,enthalpy,and entropy by 30.53,35.05 and 10.71%respectively(p<0.05).Changes in spectra of UV and fluorescence,and micrographic-imaging indicated alterations of HILMP by sonochemical-treatment.Antioxidative activity of sonochemically-treated HILMP increased,likened to control.(3)Hermetia illucens(edible insect)larvae protein,and hydrolysates were prepared using three pretreatment modes(conventional,fixed-frequency ultrasonic,and sweep-frequency).And the amino acid(AA)scores,antioxidative activity,and techno-functional property of the respective isolates and hydrolysates were investigated.Alkaline protease hydrolysis significantly enhanced protein solubility,but impaired the emulsifying property and foaming stability.Isolates and hydrolysates treated by ultrasound exhibited highest antioxidative effect,and showed excellent solubility and foam expansion over wide(2-12)pH,likened the conventional.Ultrasonic,particularly sweep-frequency,treated hydrolysates overall showed superior solubility,foam,and antioxidative(ABTS,Superoxide scavenging,and Ferric-reducing)capacity than the remaining modes and isolates(p<0.05).Treatment type influenced functional attributes and antioxidative capacity of hydrolysates and isolates.(4)The impact of conventional(control)and mixt-frequency ultrasound treatments on the structural,physical and functional traits of comestible insect(H.illucens/soldier fly)larvae protein preparations and hydrolysates were examined.Enzymolysis(especially sonication-aided)caused no significant decrease in lightness of samples compared to control(p>0.05).Sonic-treated(particularly sweep-type)isolates and hydrolysates showed significant(p<0.05)increases in thiol value,reconstitutability function(pH 2-10),and surface charge;and significant decreases in turbidity,and particle size,relative to controls.Protein isolates were characterized by higher molecular weight(Mw)using SDS-PAGE,whereas hydrolysates were lower(with no observable variances).By numerical estimation,hydrolysates(especially the sweep-treated)showed significantly lower Mw(<1000 Da).Deconvoluted FTIR spectra(?-helix,?–sheet/turn,random coil fractions),and UV spectra analyses showed differences in samples.Treatment type(sweep/fixed frequency ultrasound)could be used to alter protein structure,modify functionality,and thereby usage of H.illucens protein/hydrolysate preparations.(5)The effect of sonication conditions on antioxidant activity of Hermetia illucens larvae-meal protein hydrolysates were investigated.Three-factor-three-level:pH(7–9),time(10–30 min),and temperature(25–55°C)were optimized.Box-Behnken's design was applied to optimize sonication treatment.Ferrous-ion-chelating activity(ICA),DPPH-radical scavenging capacity(DPPHRSA),Hydroxyl-radical scavenging activity(HRSA),and cupric-ion chelating capacity(CCA)were considered as responses.Findings demonstrated that sonication preceding enzymolysis significantly impacted on ICA,DPPHRSA,HRSA,and CCA.ANOVA showed the determination-coefficient(R~2)were 0.98(ICA),0.99(DPPHRSA),0.98(HRSA),and 0.88(CCA);demonstrating that the models were reasonably fit with experimental results.Optimum sonication conditions were pH(9),time(29.84 min),and temperature(54.93°C).For these conditions,the experimental data obtained[ICA(37.84%),DPPHRSA(43.19%),HRSA(71.01%),and CCA(68.93%)]were consistent with predicted values,and higher than control(conventional).(6)The antioxidative activity(at varied concentration),physicochemical,technofunctional and structural characteristics of H.illucens larvae(HIL)protein isolates as influenced by the technique used in dehydration of HIL–freeze dried(FD),microwave dried(MD),oven dried(OD),and combination of FD and MD(FMD)were investigated.Isolate from FD HIL exhibited enhanced water absorption,solubility(pH 2-12),and decreased particle and browning index,likened to that from MD,OD,and FMD(p<0.05).FMD resulted in isolate with improved antioxidative,and oil absorption function(p<0.05).Basic structural units of the isolates,and associated spectra data:Fluorescence,FTIR,Circular Dichroism(?-helix,?-sheet,?-turn and random coil fractions)indicated variances in the samples.The choice of dehydration technique on HIL for protein preparations may,thus,be operable based on desired functionality. |
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