Formation Of Fluorescent Compounds Research Articles

Preservative Effect of Alga Flour Extract on Frozen Horse Mackerel (Trachurus trachurus) Lipids.

The aim of this study was to investigate the preservative properties of alga Gelidium sp. flour when included in the glazing medium employed for the frozen storage (-18 °C) of horse mackerel (Trachurus trachurus). Different concentrations (low, medium, and high) of an aqueous extract were tested and compared to a control water-glazing condition. Quality changes (lipid oxidation and hydrolysis, fatty acid (FA) profile, and trimethylamine (TMA) formation) were determined after 3- and 6-month storage periods. A general quality loss (lipid oxidation with hydrolysis development and TMA formation) with the frozen storage period was detected in all samples. The presence of an alga flour (AF) extract in the glazing medium led to a lower (p < 0.05) TBARS and fluorescent compound formation and to higher (p < 0.05) polyene values in frozen fish. Furthermore, a preserving effect on free fatty acids was detected in AF-treated fish. On the contrary, the AF-glazing treatment did not affect (p > 0.05) the TMA formation and the total n3/total n6 FA ratio. In general, preservative effects were found to be higher in frozen fish corresponding to the medium concentration tested. Current results show the potential of Gelidium sp. flour as a natural source of preservative hydrophilic compounds for the quality enhancement of frozen horse mackerel.

Influence of Cuttlefish-Ink Extract on Canned Golden Seabream (Sparus aurata) Quality.

Four different concentrations of an aqueous extract of cuttlefish (Sepia spp.) ink (CI) were introduced, respectively, into the packing medium employed during golden seabream (Sparus aurata) canning. The quality parameters of the resulting canned fish were determined and compared to the initial fish and the control canned muscle. An important effect of the CI concentration introduced in the packing medium was proved. The presence in the packing medium of a relatively low CI concentration (CI-2 batch) led to a lower (p < 0.05) lipid oxidation development (fluorescent compound formation), lower (p < 0.05) changes of colour parameters (L* and a* values), and lower (p < 0.05) trimethylamine values in canned fish when compared to control canned samples. Additionally, the two lowest CI concentrations tested led to higher average values of C22:6ω3, ω3/ω6 ratios, and polyene index. On the contrary, the use of the most concentrated CI extract (CI-4 condition) led to a prooxidant effect (higher fluorescence ratio value). In agreement with environmental sustainability and circular economy requirements, the study can be considered the first approach to a novel and valuable use of the current marine byproduct for the quality enhancement of canned fish. On-coming research focused on the optimisation of the CI-extract concentration is envisaged.

Influence of Different Previous Frozen Holding Periods on the Canned Fish Quality.

The combined effects of thermal processing (i.e., sterilisation treatment) and the prior frozen storage time (3 or 6 months at -18 °C) on the quality loss in canned Atlantic horse mackerel (Trachurus trachurus) were determined. Thus, the sterilisation step led to a remarkable (p < 0.05) formation in the canned fish muscle of fluorescent compounds, free fatty acids (FFAs), and trimethylamine and an increase in the L* and b* colour parameters; meanwhile, a decrease (p < 0.05) in the total ω3 FA/total ω6 FA ratio and the a* colour value were detected. The prior frozen storage period led to an increased (p < 0.05) lipid oxidation (peroxide, thiobarbituric acid reactive substance, and fluorescent compound formation) and hydrolysis (FFA formation) development and to increased L* and b* colour values in the corresponding canned samples; additionally, a lower (p < 0.05) polyene index and phospholipid content were observed in canned fish previously subjected to frozen storage. In most indices, physico-chemical changes related to quality loss were found to be higher if the previous storage period was increased. According to the marked effects of the sterilisation step and the prior frozen storage period, the optimisation of such processing conditions is recommended to maximise the quality of canned horse mackerel.

Antioxidant Activity of an Aqueous Extract of Cuttlefish Ink during Fish Muscle Heating.

The antioxidant effect of cuttlefish (Sepia officinalis) ink (CFI) was analysed in the present study. A model system consisting of minced seabream (Sparus aurata) muscle and different concentrations of an aqueous extract of CFI was subjected to a heat (50 °C) treatment for 12 days. The effects of the CFI content and the heating time on lipid oxidation (conjugated diene (CD), conjugated triene (CT), and peroxide values and fluorescent compound formation), hydrolysis (free fatty acid content) development, and changes in the fatty acid (FA) profile (polyene index (PI), unsaturated FA content, ω3/ω6 ratio) were determined. The addition of the aqueous extract of CFI led to a lower (p < 0.05) development of lipid oxidation (CD, CT, and fluorescent compound determination) and to a higher (p < 0.05) retention of unsaturated FAs (PI determination). More important effects were found with increased CFI concentrations and at advanced heating times. However, a definite effect on lipid hydrolysis development (FFA value) could not be inferred. A new approach for the beneficial use of cuttlefish ink is presented. According to the direct relationship between rancidity stability and nutritional and sensory values, the present study provides a new strategy for the quality enhancement of thermally treated seafood.

Effect of Rigor Stage and Pressurisation on Lipid Damage, Total Volatile Amine Formation and Autolysis Development in Palm Ruff Stored on Ice

The effect of the rigor stage (pre or post) and previous high-pressure processing (HPP; 450 and 550 MPa for 3 min) was checked during the storage on ice of farmed palm ruff (Seriolella violacea). Fish processed in pre-rigor conditions led to higher and lower levels (p < 0.05) of moisture and lipid contents in chilled fish, respectively, when compared to their counterpart samples processed in the post-rigor stage. Pre-rigor fish showed a higher (p < 0.05) quality level than post-rigor samples according to the assessment of the K value (59.0-92.1 and 70.3-96.3 ranges, respectively), fluorescent compounds (0.29-1.11 and 0.37-1.90 ranges, respectively), free fatty acids (FFA) (15.1-188.0 and 33.8-232.5 g·kg-1 lipids ranges, respectively), and total volatile amines (216.3-387.6 and 217.7-412.2 g·kg-1 muscle ranges, respectively). Pressure-treated fish showed higher (p < 0.05) quality retention than non-treated samples according to the formation of fluorescent compounds (0.29-0.86 and 0.85-1.90 ranges, respectively), FFA (15.1-50.6 and 58.9-223.5 g·kg-1 lipids ranges, respectively), and total volatile amines (216.3-250.3 and 351.1-412.2 g·kg-1 muscle ranges, respectively) and the evolution of the K value (59.0-77.2 and 86.9-96.3 ranges, respectively). The use of pre-rigor fish and previous HPP is recommended for the commercialisation of the current species as a fresh product.

Antioxidant Effect of Octopus Byproducts in Canned Horse Mackerel (Trachurus trachurus) Previously Subjected to Different Frozen Storage Times.

The effects on lipid damage in canned horse mackerel (Trachurus trachurus) of a prior frozen storage (-18 °C) period and the presence of an octopus (Octopus vulgaris) cooking juice (OCJ) in the packing medium were investigated. An increase of the frozen storage time favoured an increase (p &lt; 0.05) of free fatty acid (FFA), peroxide, and thiobarbituric acid reactive substance contents and a decrease (p &lt; 0.05) of the phospholipid (PL) value and polyene index. Furthermore, an increased presence of OCJ in the packing medium led to an inhibitory effect (p &lt; 0.05) on fluorescent compound formation as well as to a retention (p &lt; 0.05) of the PL and FFA compounds. Colour determination showed a substantial increase (p &lt; 0.05) of L* and b* values in canned fish with previous frozen storage time. Nevertheless, this increase was partly reduced (p &lt; 0.05) by the OCJ presence in the packing medium. It is concluded that previous holding time has led to an increased lipid oxidation development and loss of beneficial lipid constituents (i.e., PLs and polyunsaturated fatty acids). Remarkably, the presence in the packing medium of preservative compounds (i.e., antioxidants) included in waste juice obtained from octopus processing provided an effective tool for lipid preservation and quality enhancement in canned fish.

Effect of Alga Gelidium sp. Flour Extract on Lipid Damage Evolution in Heated Fish Muscle System.

This research aimed to evaluate the antioxidant properties of flour obtained from red alga Gelidium sp., which is underutilised nowadays in food applications. Thus, a model system consisting of minced mackerel (Scomber scombrus) muscle and aqueous flour extract was subjected to heating treatment (50 °C) for 11 days. Resulting levels on conjugated diene (CD) and triene (CT) contents, peroxide value, thiobarbituric acid index, and fluorescent compound and free fatty acid (FFA) formation were monitored at different heating times. As a result, the presence of the aqueous extract of the alga flour led to higher levels (p < 0.05) of primary lipid oxidation compounds (CD and CT assessment) and lipid hydrolysis (FFA content). Contrarily, alga flour addition led to lower (p < 0.05) fluorescent compound formation measured in the aqueous and organic fractions resulting from the lipid extraction of the fish muscle and in the supernatant medium corresponding to the heating reaction system. All effects were found to be more important (p < 0.05) with increased alga flour concentration and heating reacting time. According to the straight relationship between the interaction compound formation and nutritional and sensory values, this study opens the way to the quality enhancement of thermally treated seafood by the addition of flour extract from Gelidium sp.

Antimicrobial and antioxidant effect of lyophilized Fucus spiralis addition on gelatin film during refrigerated storage of mackerel

Lyophilized alga Fucus spiralis powder was incorporated into a gelatin-based film and employed as a packaging system for mackerel ( Scomber scombrus ) muscle portions throughout a 9-day refrigerated storage period at 4 °C. In global terms, a progressive loss of quality could be observed in fish muscle with increasing storage time. Comparisons between batches allowed us to conclude an inhibitory effect of F. spiralis -containing films on microbial activity (assessment of aerobes, psychrotrophs, and proteolytic bacteria) and on lipid hydrolysis (as determined by free fatty acid formation) in mackerel muscle. The presence of the lyophilized macroalga in the packaging film also led to a higher retention of primary (peroxides) and secondary (thiobarbituric acid reactive substances) lipid oxidation compounds, while the formation of fluorescent compounds (interaction compounds between lipid oxidation compounds and nucleophilic molecules present in the fish muscle) decreased. Both antimicrobial and antioxidant effects were more intense when the concentration of alga in the packaging film was increased. The preservative effect resulting from the presence of F. spiralis in gelatin-based films demonstrates the potential employment of such bioactive films to improve the retention of fish quality and enhance its commercial value. • Lyophilized Fucus spiralis was incorporated into a gelatin packaging film. • F. spiralis in the packaging film inhibited free fatty acid formation in mackerel. • F. spiralis inhibited aerobes, psychrotrophs, and proteolytic bacteria in fish muscle. • F. spiralis in the packaging film inhibited fluorescent compound formation. • Superior retention of primary and secondary lipid oxidation compounds was observed.

Effect of Prior Chilling Period and Alga-Extract Packaging on the Quality of a Canned Underutilised Fish Species.

The effect of a prior chilling period and an alga extract packaging on the quality of a canned underutilised mackerel species (Scomber colias) was investigated. For this different chilling times (0, 4 and 9 days) were taken into account and three concentrations of aqueous extracts of the macroalga Fucus spiralis were tested in a brine-packaging medium. Chemical changes related to quality were analysed after 3 months of canned storage. A substantial increase (p < 0.05) in free fatty acid content was observed in canned fish by increasing the chilling time; however, alga extract presence in the packaging medium led to decreased mean values. Concerning lipid oxidation development, an increased chilling time led to higher values (p < 0.05) of thiobarbituric acid index and fluorescent compounds formation; remarkably, an increased presence of alga extract led to a higher (p < 0.05) peroxide retention and lower (p < 0.05) fluorescent compounds content. Average colour L* and a* values showed a decrease and an increase, respectively, with chilling time; however, such changes were minimised with the alga extract content in the packaging system. Trimethylamine content revealed a marked increase as a result of the sterilisation step, but no influence (p > 0.05) of the chilling time or the alga-packaging medium could be implied.

The Effect of Gelatine Packaging Film Containing a Spirulina platensis Protein Concentrate on Atlantic Mackerel Shelf Life.

The use of packaging films containing natural preservative compounds attracts great attention for the quality improvement of seafood. Microalga spirulina (Spirulina platensis) represents a potential source of high added-value and preservative biocompounds. The goal of this study was to enhance the quality of refrigerated Atlantic mackerel (Scomber scombrus) by including a protein concentrate (PC) of spirulina in a gelatine-based film. Quality changes in fish muscle were monitored by microbial and chemical analyses throughout an 11-day refrigerated storage (4 °C). As a result of the presence of spirulina PC in the film, an antimicrobial effect (p < 0.05) was concluded as determined by comparative evolution of aerobes and psychrotrophs, while no effect (p > 0.05) was concluded for Enterobacteriaceae, proteolytics and lipolytics counts. Furthermore, a lower (p < 0.05) formation of trimethylamine and free fatty acids was detected. Lipid oxidation, measured by fluorescent compounds formation, also exhibited lower average values in fish corresponding to the batch containing spirulina concentrate. The preservative effects observed can be explained on the basis of the presence of antimicrobial and antioxidant compounds in the microalga concentrate. It is proposed that the current packaging system may constitute a novel and promising strategy to enhance the quality of commercial refrigerated fatty fish.

Preservative Effect of Algae Extracts on Lipid Composition and Rancidity Development in Brine‐Canned Atlantic Chub Mackerel (Scomber colias)

This research focuses on the lipid fraction and the rancidity stability of commercial canned Atlantic Chub mackerel (Scomber colias). For it, two different concentrations of aqueous extracts of two abundant algae (Fucus spiralis and Ulva lactuca) are included in the brine‐packing (aq. 2% NaCl) medium during mackerel canning. Quality analyses are carried out after a 3‐month canned storage (20 °C). Phospholipids, sterols, and α‐tocopherol contents show a marked loss as a result of canning, this loss being mostly inhibited when considering the canned fish packed in the presence of the most concentrated algae extracts. Breakdown of free fatty acids and peroxides produced during the thermal treatment is inhibited by the presence of the algae extracts, a higher retention of such molecules being observed by increasing the algae extract concentration. Analysis of fluorescent compounds formation (tertiary lipid oxidation) shows a marked increase after canning, this increase being partly inhibited by the presence of antioxidant compounds present in the algae extracts; interestingly, oxidation inhibition is found more important in canned fish corresponding to F. spiralis batches than U. lactuca. A preservative effect on lipid constituents and rancidity development is concluded by the presence of algae extracts in the packing medium.Practical Applications: The extensive heat treatment involved during fish canning has been reported to produce breakdown of constituents, lipid damage (oxidation and hydrolysis) development showing a marked effect on nutritional and sensory properties; furthermore, this effect has shown to be greater when a brine medium is applied as packing system. Marine algae have been described as being a relevant source of chemical constituents including an antioxidant and antibacterial behavior. In the current work, employment of a commercial brine‐packing including aqueous algae extracts shows a preservative effect on the lipid fraction (composition and rancidity stability) during the canning process of Atlantic Chub mackerel. The proposed strategy may open the way to the development of a natural biopreservation for commercial canned fish due to the simple methodology employed and the abundancy of the two algae chosen for the study. Further research should envisage optimization of the preservative compounds extraction by advanced technologies.Aqueous extracts of algae Fucus spiralis and Ulva lactuca are included in the packing medium during Atlantic Chub mackerel (Scomber colias) canning. As a result, an inhibitory effect on lipid composition changes and rancidity development is obtained. Better results are observed by employing alga F. spiralis.

Effectiveness of a combined ethanol–aqueous extract of alga Cystoseira compressa for the quality enhancement of a chilled fatty fish species

Seaweeds have attracted an increasing attention as a new source for bioactive compounds, these include preservative compounds. This study is a first attempt to employ alga Cystoseira compressa for the preservation of chilled fish. For it, a combined ethanol–aqueous extract of this alga was included in the icing system and employed as chilling medium for the storage of horse mackerel (Trachurus trachurus) for 11 days. On the basis of the microbial groups (aerobes, psychrotrophs, proteolytic, lipolytic and Enterobacteriaceae bacteria) assessed, an inhibitory effect (p < 0.05) on microbial activity in horse mackerel muscle was observed as a result of including the alga extract in the icing medium; such preservative effect was also proved by chemical determinations related to microbial activity (pH and trimethylamine values). Additionally, a significant decrease (p < 0.05) of lipid hydrolysis (free fatty acids formation) and oxidation (fluorescent compounds formation) in fish was also observed as a result of the presence of C. compressa extracts in the icing medium. The icing medium proposed in this work (i.e., the combination of ethanolic and aqueous extracts of C. compressa) may constitute a promising strategy to the application of natural algae extracts for fatty fish storage and enhance quality retention during commercialisation.

Structural changes and functional properties of highly concentrated whey protein isolate-citrus pectin blends after defined, high temperature treatments

Extrusion processing can be used for conjugation of whey proteins with citrus pectins. However, many reactions can take place simultaneously, and so far less is known about the influence of the extrusion parameters on the structural and functional properties of the reaction products. This study focuses on the influence of elevated temperatures on the structural and functional properties of highly concentrated whey protein isolate-citrus pectin blends. Defined temperature treatments were performed by using a closed-cavity rheometer. Structural changes due to non-disulfide, covalent cross-links, and the formation of fluorescent compounds were analyzed. Functional properties (e.g. viscosity, emulsifying capacity) were determined of selected samples. The results showed that the emulsifying capacity can be improved by defined temperature treatments at 120 °C and 140 °C. Samples with an improved emulsifying capacity also exhibited higher maximum fluorescence intensity indicating the formation of Maillard reaction products (e.g. conjugates).

Prevention of in vitro oxidation of low density lipoproteins (LDL) by amaranth peptides released by gastrointestinal digestion

The objective of this work was to analyze the capacity of amaranth peptides generated by gastrointestinal digestion to prevent LDL oxidation. A simulated gastrointestinal digest from protein isolate (Id); Id fractions separated by gel filtration FPLC, and synthetic peptides (products of digestion) were evaluated. The evolution of conjugated dienes (CD) and, for most active samples, TBARS, fluorescent compounds (FC) evolution and electrophoretic mobility (EM) during Cu+2/H2O2-induced-LDL-oxidation were evaluated. Id was able to increase the lag time and to decrease the propagation rate for CD and FC formation; however, EM was not modified. Most active FPLC fractions (0.59–1.4kDa) attained a complete inhibition of CD, and partial or total prevention of FC formation and electrophoretic changes. Peptides evaluation indicated that the presence of histidine, hydrophobic and aromatic residues would be important in the inhibition of Cu+2/H2O2-induced LDL oxidation. The most active were cationic or neutral peptides.

Characterization of the quality of novel rye-buckwheat ginger cakes by chemical markers and antioxidant capacity

AbstractThe total phenolics and flavonoids, rutin, early, advanced and finalMaillard reaction products, and antioxidative capacity determined against 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) radical cation and superoxide anion radicals were used for the characterization of the quality of novel rye-buckwheat ginger cakes enriched with rutin (quercetin rutinoside). The cakes were prepared substituting 30 % of rye flour by light buckwheat flour or flour from roasted buckwheat dehulled grains and employing a dough fermentation-like incubation step. Enrichment of ginger cakes with rutin showed protective effect on lysine blockage, improved antioxidant properties, inhibited the formation of furosine and free fluorescent compounds thus stimulating the Maillard reaction progress towards melanoidin formation. The loss of the nutritional quality of cakes enriched with rutin was related to the formation of fluorescent compounds linked to protein and carboxymethyllysine at an advanced stage of the Maillard reaction. It can be concluded that free fluorescence intermediatory compounds, carboxymethyllysine and browning are the best chemical markers for the characterization of the quality of this novel type of ginger cakes. This study also indicates that rye-buckwheat ginger cakes enriched with rutin can be recommended for wider consumption since daily consumption of 250 g of these cakes may have a prophylactic or therapeutic effect corresponding to typical pharmacological drugs with rutin as the active component.

Effect of biodegradable film (lyophilised alga Fucus spiralis and sorbic acid) on quality properties of refrigerated megrim (Lepidorhombus whiffiagonis)

SummaryThe effect of replacing the on‐board currently employed polyethylene film by a novel type of environmentally friendly packaging was studied. For it, a polylactic acid (PLA) biodegradable film including lyophilised alga Fucus spiralis and sorbic acid was applied during megrim (Lepidorhombus whiffiagonis) refrigeration and its effect on fish quality loss was evaluated. Thus, sensory assessment showed that samples wrapped up with PLA film including 8% alga and 1% sorbic acid were still acceptable on day 11, while control fish specimens (kept under polyethylene film) were rejected at that time. Under such biodegradable film condition, a preservative effect was also implied according to chemical indices assessment related to microbial activity (trimethylamine–N) and lipid oxidation development (peroxide and fluorescent compounds formation); additionally, lower mean numbers for different microbiological groups (aerobes, Enterobacteriaceae and psychrotrophs) were detected. This result provides a promising replacement strategy to enhance refrigerated fish quality and reduce the waste material content.

Inhibition of quality loss in chilled megrim (Lepidorhombus whiffiagonis) by employing citric and lactic acid icing

SummaryThis study focuses on the quality retention of megrim (Lepidorhombus whiffiagonis) during chilled storage. Aqueous solutions of two different concentrations of citric (CA) and lactic (LA) acids were employed as icing media (0.125% CA–0.050% LA and 0.175% CA–0.050% LA, respectively; w/v). The effects of each solution on microbial activity, lipid damage and sensory acceptance were monitored for up to 13 days of storage. Lower (P &lt; 0.05) bacterial growth was detected according to microbiological (aerobe and psychrotroph counts) and chemical (trimethylamine‐N and pH) assessments, which led to an enhancement of sensory appreciation. Whereas control fish were determined as unacceptable at day 13, the acid‐iced fish were still acceptable at that time. Concerning lipid damage, an inhibitory effect (P &lt; 0.05) on fluorescent compound formation was observed in the acid‐iced fish. Present results allow to conclude that the use of a CA–LA icing system can provide a profitable strategy to obtain higher quality chilled fish.

Extension of the shelf life of chilled hake (Merluccius merluccius) by a novel icing medium containing natural organic acids

Three combinations of two natural organic acids, citric acid (CA) and lactic acid (LA), in the form of novel flake icing systems were evaluated for the preservation of European hake (Merluccius merluccius), one of the most commercialised gadoid fish species in Europe. The flake icing systems were prepared with fresh water and 0.075%/0.050% (C-75 batch), 0.125%/0.050% (C-125 batch) and 0.175%/0.050% (C-175 batch) CA/LA, respectively. Aerobic mesophiles, psychrotrophs, proteolytic bacteria, anaerobes, Enterobacteriaceae, trimethylamine, lipid hydrolysis, primary, secondary and tertiary lipid oxidation events, and pH levels were evaluated in hake muscle in all batches during 13 d of chilled storage and the results were compared with sensory analyses. Significantly (p < 0.05) lower microbial counts were found in the C-175 batch for all five microbial groups investigated when compared with the control batch, with differences between batches of greater than 2 log CFU/g in the case of aerobes and anaerobes. The presence of organic acids in the icing systems also inhibited (p < 0.05) the increase in trimethylamine-nitrogen (TMA-N) content, with greater inhibition as the CA concentration in the ice increased. An inhibitory effect (p < 0.05) on fluorescent compound formation due to the presence of organic acids in the icing systems, which is indicative of tertiary lipid oxidation, was also observed at advanced storage times. These results correlated well with sensory analysis, which revealed that the shelf lives of the C-125 and C-175 batches were extended. The melting of the ice crystals containing the natural organic acid solutions, especially in the C-175 batch, exerted an antimicrobial washing effect that may explain the better protection of hake quality when stored in the proposed flake icing system.

Preservative effect of an organic acid‐icing system on chilled fish lipids

AbstractThis study provides a first approach concerning a novel chilling strategy, which employs a mixture of different preservative organic acids (ascorbic, citric and lactic) in the icing medium. Thus, ice prepared from water including two different concentrations of a commercial acid mixture‐formula (800 and 400 ppm; C‐800 and C‐400 conditions, respectively) were applied as icing system to three important commercial fish lean species (hake, Merluccius merluccius; megrim, Lepidorhombus whiffiagonis; angler, Lophius piscatorius). Lipid oxidation (peroxide value; thiobarbituric acid index; fluorescent compound formation) and hydrolysis (free fatty acid formation) were evaluated throughout the chilling time (up to 12–15 days) and compared to results obtained in fish kept under traditional ice prepared only from water (C‐0 condition); a complementary sensory evaluation was carried out. As a result of employing the C‐800 icing condition, a partial inhibition of lipid oxidation and hydrolysis development was obtained that was accompanied by a shelf life enhancement in all cases. Further research taking into account the complementary action of the present organic acids is envisaged. According to the lipid damage analysis, lipid hydrolysis was a more relevant event than lipid oxidation in all fish species tested.

A generic procedure to monitor Maillard-derived fluorescent compounds in cookies by flow-injection analysis

Flow-injection analysis is proposed for routine measurement of Maillard-derived fluorescent compounds (FC) in cookies as a marker of the extent of baking. In addition, procedure was applied to investigate the formation of free and total (bound to protein free) FC in cookie-resembling models and in commercial wheat-based cookies as well. FC accounts for the overall fluorescence response of Maillard-derived fluorescent compounds (bound or not to protein) formed during baking but not for a single compound. Free and total FC values increased exponentially during baking at 200, 210 and 220 °C and an induction period of 10 min was observed for free FC. In the complex scenario of the progress of the Maillard reaction (MR) during baking, formation of FC (347/415, ext/emm) was not the limiting step for browning development at the advanced stage of the reaction. Furthermore, the formation of Maillard-derived fluorescent compounds and browning during baking were a consequence of parallel reactions apart from the classical MR scheme of consecutive reactions. Total/free FC ratio was dependent on the baking conditions applied and ratio was significantly decreased at severe baking conditions. Total/free FC ratio could be used as a reference marker for monitoring the process and to identify potential over-processing situations during baking. In addition, fluorescent residues were originally bound to protein because total/free FC ratio decreased drastically as increased the temperature and time of the process. Levels of total FC were nearly 20-fold of free FC in commercial samples. Values of FC were positively correlated with acrylamide, a Maillard-derived food processing contaminant.