Investigation of the possibility of maize germ oil bodies’ incorporation into edible biopolymer-based systems

Effective extraction of oil bodies from maize germ and their exploitation in the preparation of novel food products was the main goal of the thesis. In this respect, the optimization of the maize germ oil bodies’ aqueous extraction, in order to maximize the yield of the process, was fist pursued by employing statistical tools such as the Taguchi methodology and response surface methodology. Aqueous extraction of oil bodies was favoured at alkaline conditions and fine grinding of the raw material. Extraction time and repeated cycles of extraction had a positive strong effect on the yield of the process. The oil was extracted from the germ almost quantitatively in the form of a natural emulsion of intact small sized oil bodies dispersed in an exogenous protein solution. The economic potential of the proposed method is promising for future implementation. In the next stage of the thesis, oil body-based cream, stabilized with sodium caseinate was dried and the resulting powder was evaluated in terms of its handling and reconstitution properties. The oil bodies emulsion was dehydrated by oven heating at 40 oC followed by grinding or by spray drying using Nano Spray Dryer B-90. The method of drying had an effect on the handling and reconstitution properties of both the powders due to the different size of the dry particles. Finally, oil bodies were exploited in the form of a cream free from exogenous proteins or in the form of a “milk” rich in exogenous proteins in order to develop and characterize a composite sodium caseinate-based edible film, plasticized with glycerol. The film prepared with oil bodies’ cream exhibited good mechanical properties and better water barrier properties, compared to sodium caseinate films. Homogenization of the film-forming solution to obtain films with improved characteristic was not needed. The physical properties of the composite films based on oil bodies “milk” changed during the period of 70 days aging. Oil bodies creaming is likely to be the reason for changes observed in the composite films. Water exchange with the environment and possible glycerol movement seemed to be the main causes for the changes in physical properties of the both the control as well as the composite films.Ο κύριος σκοπός της εργασίας ήταν η αποτελεσματική εκχύλιση ελαιοσωμάτων από φύτρο αραβοσίτου και η αξιοποίησή τους στην παρασκευή καινοτόμων προϊόντων τροφίμων. Ο πρώτος στόχος ήταν η μεγιστοποίηση της απόδοσης της υδατικής εκχύλισης ακέραιων ελαιοσωμάτων από φύτρο αραβοσίτου μετά από αναγνώριση των κύριων παραμέτρων που επιδρούν στη διεργασία της υδατικής εκχύλισης των ελαιοσωμάτων και τη βελτιστοποίησή της. Για την υλοποίηση του στόχου, αξιοποιήθηκαν στατιστικά εργαλεία πειραματικού σχεδιασμού σύμφωνα με τη μέθοδο Taguchi και του σύνθετου πειραματικού σχεδιασμού σε συνδυασμό με τη μέθοδο απόκρισης επιφανειών (RSM). Η υδατική εκχύλιση ελαιοσωμάτων φύτρου αραβοσίτου ευνοείται όταν γίνεται καλή κατάτμηση του φύτρου και όταν πραγματοποιείται σε αλκαλικές συνθήκες. O χρόνος της εκχύλισης έχει την ισχυρότερη θετική επίδραση στην απόδοση της διεργασίας και ακολουθεί ο αριθμός των κύκλων εκχύλισης. Το έλαιο που βρίσκεται στα κύτταρα του φύτρου αραβοσίτου μπορεί να εκχυλιστεί σχεδόν ποσοτικά με τη μορφή γαλακτώματος ακέραιων και μικρού μεγέθους ελαιοσωμάτων. Το εγχείρημα που προτείνεται φαίνεται να έχει θετικό δυνητικό οικονομικό ισοζύγιο. Ο επόμενος στόχος της διατριβής ήταν η εξέταση της δυνατότητας μετατροπής των ελαιοσωμάτων από φύτρο αραβοσίτου, απαλλαγμένων από εξωγενείς πρωτεΐνες, σε ένα αφυδατωμένο προϊόν με τη μορφή σκόνης και η μελέτη των ιδιοτήτων χειρισμού και επαναδιασποράς της σε νερό. Η αφυδάτωση της κρέμας ελαιοσωμάτων έγινε με θέρμανση και άλεση ή με αφυδάτωση με καταιονισμό σε Nano Spray Dryer B-90. Η αφυδάτωση γαλακτώματος ελαιοσωμάτων οδηγεί στην παρασκευή αφυδατωμένης σκόνης πλούσιας σε ελαιοσώματα. Η μέθοδος με την οποία αφυδατώνεται το γαλάκτωμα επιδρά στο μέγεθος των κόκκων της σκόνης που, τελικά, επηρεάζει τις ιδιότητες χειρισμού και επαναδιασποράς της σε νερό της. Η τελική επιδίωξη της διατριβής ήταν η αξιοποίηση των ελαιοσωμάτων στην ανάπτυξη καινοτομικής σύνθετης εδώδιμης μεμβράνης με βάση το καζεϊνικό νάτριο που να παρουσιάζει μειωμένη διαπερατότητα στους υδρατμούς και ο χαρακτηρισμός της ως προς τις λειτουργικές της ιδιότητες. Η ενσωμάτωση ελαιοσωμάτων από φύτρο αραβοσίτου στη δομή εδώδιμης μεμβράνης με βάση το καζεϊνικό νάτριο, πλαστικοποιημένης με γλυκερόλη, ήταν επιτυχής, τόσο στην περίπτωση που τα ελαιοσώματα βρισκόταν με τη μορφή κρέμας ελεύθερης εξωγενών πρωτεϊνών όσο και στην περίπτωση που ήταν με τη μορφή γάλακτος πλούσιου σε εξωγενείς πρωτεΐνες. Οι σύνθετες μεμβράνες που παρασκευάστηκαν με ενσωμάτωση κρέμας ελαιοσωμάτων είχαν καλή μηχανική συμπεριφορά και βελτιωμένη ικανότητα φραγής έναντι της διέλευσης του νερού. Πολύ μεγάλης τεχνολογικής σημασίας είναι το συμπέρασμα ότι παρασκευή σύνθετων μεμβρανών με πολύ καλές ιδιότητες μπορεί να γίνει χωρίς την εφαρμογή ομογενοποίησης στο αρχικό γαλάκτωμα. Οι εδώδιμες μεμβράνες με βάση το καζεϊνικό νάτριο μεταβάλλουν τις ιδιότητές τους κατά την αποθήκευσή. Η αλληλεπίδραση της σχετικής υγρασίας του περιβάλλοντος με τη δομή της μεμβράνης και η μετακίνηση της γλυκερόλης φαίνεται ότι παίζουν σημαντικό ρόλο στη μεταβολή αυτή στις απλές μεμβράνες, ενώ η μετακίνηση των ελαιοσωμάτων φαίνεται ότι είναι ο κύριος λόγος στο οποίο οφείλονται οι μεταβολές στην περίπτωση των σύνθετων μεμβρανών

Characterization of <i>Tenebrio molitor</i> Larvae Protein Preparations Obtained by Different Extraction Approaches

Edible insects have recently attracted research attention due to their nutritional value and low environmental footprint. Tenebrio molitor larva was the first insect species to be classified by European Food Safety Authority (EFSA) as safe for human consumption. However, it is thought that the incorporation of edible insect as an ingredient in a food product would be more appealing to consumers than being visible. The aim of the present study was to determine the physicochemical properties of the larvae meal and protein concentrates. Different methods to extract and recover proteins from defatted (DF) Tenebrio molitor larvae were applied; i.e., alkaline extraction (DF-ASP); isoelectric precipitation after alkaline extraction (DF-AIP); and NaCl treatment (DF-SSP), and the obtained protein fractions were characterized. The DF-ASP exhibited the highest protein extraction/recovery efficiency (>60%), while it was the most effective in decreasing the interfacial tension at the oil/water (o/w) interface. The DF-AIP had the highest protein content (75.1%) and absolute values of ζ-potential and the best ability to retain water (10.54 g/g) and stabilize emulsions at pH 3.0. The DF-SSP protein preparation had the highest oil binding capacity (8.62%) and solubility (~88%) at acidic pHs and the highest emulsifying activity (~86 m2/g). Electrophoresis of the protein preparations revealed proteins with different molecular weights, while the protein secondary structure was dominated by β-structures and α-helix. Protein concentrates with different properties were able to be recovered from Tenebrio molitor larvae, that could affect their interactions with other food ingredients and their behavior during processing or storage. These findings would be valuable guidance for the technological exploitation of larvae protein preparations in the development of food formulations

Composite gels structured by a gelatin protein matrix filled with oil bodies

Oil body extracts from sesame seeds and hazelnuts were subjected to centrifugation to recover oil body concentrated creams, which were then suitably diluted with gelatin solutions to prepare mixtures of 25.0. wt% of oil and 2.0-6.0. wt% of gelatin. The gelling behaviour of the mixtures was followed by applying dynamic rheometry while gradually lowering the temperature down to 4. °C to allow network formation. The composite gels based on the oil body cream was composed of adequately dispersed oil droplets within a continuous gelatin matrix. The oil droplet incorporation brought about a significant shortening in the gelation time (20-30%) of gelatin and an increase in the gelling temperature of more than 30%. In addition, the incorporation of the naturally emulsified oil droplets at lower gelatin contents led to a limited but significant strengthening of the gelatin gel structure, indicated by an increase in the storage modulus. These results suggest that the extracted oil bodies are incorporated within the matrix, and function as active fillers of the composite gel

Single Origin Coffee Aroma: From Optimized Flavor Protocols and Coffee Customization to Instrumental Volatile Characterization and Chemometrics

In this study, the aroma profile of 10 single origin Arabica coffees originating from eight different growing locations, from Central America to Indonesia, was analyzed using Headspace SPME-GC-MS as the analytical method. Their roasting was performed under temperature–time conditions, customized for each sample to reach specific sensory brew characteristics in an attempt to underline the customization of roast profiles and implementation of separate roastings followed by subsequent blending as a means to tailor cup quality. A total of 138 volatile compounds were identified in all coffee samples, mainly furan (~24–41%) and pyrazine (~25–39%) derivatives, many of which are recognized as coffee key odorants, while the main formation mechanism was the Maillard reaction. Volatile compounds’ composition data were also chemometrically processed using the HCA Heatmap, PCA and HCA aiming to explore if they meet the expected aroma quality attributes and if they can be an indicator of coffee origin. The desired brew characteristics of the samples were satisfactorily captured from the volatile compounds formed, contributing to the aroma potential of each sample. Furthermore, the volatile compounds presented a strong variation with the applied roasting conditions, meaning lighter roasted samples were efficiently differentiated from darker roasted samples, while roasting degree exceeded the geographical origin of the coffee. The coffee samples were distinguished into two groups, with the first two PCs accounting for 73.66% of the total variation, attributed mainly to the presence of higher quantities of furans and pyrazines, as well as to other chemical classes (e.g., dihydrofuranone and phenol derivatives), while HCA confirmed the above results rendering roasting conditions as the underlying criterion for differentiation

Compositional, volatile, and structural features of Hermetia illucens (black soldier fly) flours: The effect of population and life stages

The scope of the present study was to study the effect of different populations of Hermetia illucens, commonly known as black soldier fly (BSF), on the major components and volatile composition of the derived freeze-dried flours. Potential differences in the composition of different life cycle stages of BSF, i.e., larvae and pupae, were also investigated. The flours obtained from larvae of two BSF populations from Greece (GR) and Portugal (PO) (L-GR and L-PO, respectively) demonstrated similar major chemical compositions. Pupae (Pu-PO) were richer in chitin compared to larvae. Differences were spotted in their fatty acid profiles and volatile fractions. The saturated/unsaturated lipid fraction ratio was 1.5 in L-GR, higher in L-PO (2.5), and even higher in the case of Pu-PO (4.0). Seventeen (17) compounds were detected in the volatile fraction of the Pu-PO samples and 24 in the volatile fraction of the L-GR and L-PO samples. Notably, dodecanoic acid ethyl ester was the predominant volatile compound in all samples. The proteins of both larvae and pupae were dominated by β-sheet structures. The present study's findings are valuable for designing food or feed products based on BSF components and could be important for applying suitable manufacturing and processing procedures