Exploring the use of currant pomace in foods is favourable due to its nutritional profile but also for economic and sustainability aspects. This by-product of fruit juice processing contains in addition to the dominating dietary fibre fraction considerable amounts of fat, protein, and polyphenols that are lost when the pomace is disposed of. Regardless of the intended use, the perishable material must be dried immediately or alternatively preserved. Three processing strategies (A, B, C) with different energy input and impact were outlined and related applications were implemented. The minimal (A) and intensive scenario (B) were examined comprehensively, whereas the complex processing (C) was considered only theoretically.
For a prospective use in low-cost products (A), whole dry pomace was ground using various technologies. Ready-to-use powders were obtained by impact milling below 1 mm or simultaneous drying and grinding in a turbo rotor mill. A wide range of applications is possible, especially in baked products. The powder was used to partially replace flour in bread by considering its high water-binding capacity. In the example of wheat bread, 10% flour were simply replaced with pomace and dough handling properties (reduced stickiness) as well as bread quality parameters (lower baking loss, moister crumb) were improved by pre-hydration of the pomace in hot water.
To expand the applicability of the pomace in the intensive scenario (B), the seeds were separated prior to milling and the remaining fibre fraction was treated thermomechanically either by planetary ball milling or extrusion cooking. This processing resulted in high fibre material with increased swelling capacity and water solubility. Based on the micronised seedless pomace, sweet creamy spreads were designed as an application example and the effects on rheology and physical stability were characterised. The pomace below 30 μm performed very well in spreads where it decreased oil separation. When it comes to zero-waste concepts, the seeds can be used for oil extraction whereas the stabilising effects of the fibre fraction may also be exploited to counteract sedimentation in aqueous suspensions and emulsions after pressure homogenisation.:1 Motivation
2 Literature review
2.1 Cultivation and processing of currants
2.2 Composition of currant pomace
2.2.1 Dietary fibre
2.2.2 Lipophilic components
2.2.3 Proteins, sugars, and minerals
2.2.4 Polyphenols and antioxidant capacity
2.3 Residues of toxicological importance
2.4 Preservation and comminution of food processing by-products
2.4.1 Drying
2.4.2 Particle size reduction
2.5 Extraction and fractionation of selected pomace components
2.5.1 Soluble and insoluble dietary fibre
2.5.2 Seed oil
2.5.3 Proteins
2.5.4 Anthocyanins
3 Objectives of the thesis
4 Materials and Methods
4.1 Origin of currant pomace
4.2 Processing of pomace
4.2.1 Minimal processing: Drying and milling
4.2.2 Intensive processing: Thermo-mechanical treatment of dried pomace
4.3 Pomace analysis
4.3.1 Proximate composition
4.3.2 Contamination analysis
4.3.3 Physical properties
4.3.4 Techno-functional properties
4.4 Food applications: Preparation and analysis
4.4.1 Preparation of wheat bread
4.4.2 Dough expansion, pH, and rheology
4.4.3 Bread appearance and texture
4.4.4 Preparation of sweet spreads
4.4.5 Spread analysis
4.5 Statistics
5 Results and discussion
5.1 Natural variation of currant pomace composition
5.2 Minimal processing scenario
5.2.1 Preservation of fresh pomace by convection drying
5.2.2 Milling techniques to obtain ready-to-use pomace powder
5.2.3 Hydration properties of pomace powders
5.3 Application of minimally processed pomace powder in wheat bread
5.3.1 Hydration properties and rheology during simulated baking
5.3.2 Changes in dough properties during proofing
5.3.3 Effects on bread characteristics
5.4 Intensive processing scenario
5.4.1 Composition of seedless currant pomace
5.4.2 Impact of HTST-extrusion
5.4.3 Influence of planetary ball milling on particle size
5.4.4 Modified functionality after thermo-mechanical treatments
5.5 Application of intensively processed pomace in fat-based spreads
5.5.1 Wet ball milling in oil-suspension
5.5.2 Rheological properties and physical stability of sweet spreads
5.5.3 Sensory attributes of pomace spreads
5.6 Concepts for the implementation of zero-waste strategies
6 Conclusions
Bibliography
List of figures
List of tables
Appendix
List of publications / Die Verwertung von Johannisbeertrester in Lebensmitteln bietet sich nicht nur aufgrund seines Nährstoffprofils an, sondern ist auch im Sinne der Nachhaltigkeit und unter wirtschaftlichen Aspekten vorteilhaft. Das bei der Fruchtsaftherstellung anfallende Nebenprodukt besteht überwiegend aus Ballaststoffen sowie nennenswerten Mengen an Fett, Protein und Polyphenolen, welche im Falle einer Entsorgung für die menschliche Ernährung verloren gehen. Ganz unabhängig von der weiteren Nutzung muss der leicht verderbliche Trester zunächst getrocknet oder alternativ haltbar gemacht werden. Es wurden drei Aufarbeitungsstrategien (A, B, C) entworfen, welche sich in Energieaufwand und Intensität unterscheiden. Davon wurden das sogenannte minimale (A) und das intensive Szenario (B) inklusive entsprechender Anwendungen umfassend untersucht, während eine komplexe Verarbeitung (C) nur theoretisch betrachtet wurde.
Für den Einsatz in niedrigpreisigen Lebensmitteln wurde getrockneter Trester im Gesamten (A) unter Anwendung verschiedener Technologien vermahlen. Direkt verwendbare Tresterpulver unter 1 mm wurden durch Vermahlung in einer Prallmühle oder mittels Mahltrocknung hergestellt. Es bieten sich eine ganze Reihe von Anwendungen, vor allem im Bereich der Backwaren, an. Unter Berücksichtigung der hohen Wasserbindekapazität erfolgte der Einsatz des Pulvers als Mehlsubstituent in Brot. Im Fall von Weizenbrot konnten 10% Mehl problemlos durch Trester ersetzt werden, wobei die Verarbeitungseigenschaften des Teigs (verminderte Klebrigkeit) und qualitätsbestimmende Broteigenschaften (geringerer Backverlust, feuchtere Krume) durch Vorquellen in heißem Wasser verbessert werden konnten.
Um die Einsatzmöglichkeiten des Tresters zu erweitern, wurden im intensiven Verarbeitungsszenario (B) die Samen abgetrennt und die verbleibende Faserfraktion thermo-mechanisch behandelt, zum einen in einer Planetenkugelmühle, zum anderen durch Extrusion. Die intensive Aufarbeitung resultierte in einer ballaststoffreichen Faserfraktion mit erhöhtem Quellvermögen sowie höherer Wasserlöslichkeit. Als Einsatzbeispiel wurden ausgehend von der feinstvermahlenen Faserfraktion süße Streichcremes entwickelt, und die Auswirkungen des Tresters auf Rheologie und physikalische Stabilität charakterisiert. Der Trester unter 30 μm eignete sich hervorragend in der Herstellung von fettreichen Aufstrichen, da die Ölseparation vermindert wurde. Eine möglichst umfassende, reststofffreie Verwertung des Tresters (zero-waste) kann durch Nutzung der Samen zur Ölgewinnung erfolgen, wohingegen die stabilisierenden Eigenschaften der Faserfraktion nach Hochdruckhomogenisierung auch in wässrigen Suspensionen und Emulsionen ausgeschöpft werden könnten.:1 Motivation
2 Literature review
2.1 Cultivation and processing of currants
2.2 Composition of currant pomace
2.2.1 Dietary fibre
2.2.2 Lipophilic components
2.2.3 Proteins, sugars, and minerals
2.2.4 Polyphenols and antioxidant capacity
2.3 Residues of toxicological importance
2.4 Preservation and comminution of food processing by-products
2.4.1 Drying
2.4.2 Particle size reduction
2.5 Extraction and fractionation of selected pomace components
2.5.1 Soluble and insoluble dietary fibre
2.5.2 Seed oil
2.5.3 Proteins
2.5.4 Anthocyanins
3 Objectives of the thesis
4 Materials and Methods
4.1 Origin of currant pomace
4.2 Processing of pomace
4.2.1 Minimal processing: Drying and milling
4.2.2 Intensive processing: Thermo-mechanical treatment of dried pomace
4.3 Pomace analysis
4.3.1 Proximate composition
4.3.2 Contamination analysis
4.3.3 Physical properties
4.3.4 Techno-functional properties
4.4 Food applications: Preparation and analysis
4.4.1 Preparation of wheat bread
4.4.2 Dough expansion, pH, and rheology
4.4.3 Bread appearance and texture
4.4.4 Preparation of sweet spreads
4.4.5 Spread analysis
4.5 Statistics
5 Results and discussion
5.1 Natural variation of currant pomace composition
5.2 Minimal processing scenario
5.2.1 Preservation of fresh pomace by convection drying
5.2.2 Milling techniques to obtain ready-to-use pomace powder
5.2.3 Hydration properties of pomace powders
5.3 Application of minimally processed pomace powder in wheat bread
5.3.1 Hydration properties and rheology during simulated baking
5.3.2 Changes in dough properties during proofing
5.3.3 Effects on bread characteristics
5.4 Intensive processing scenario
5.4.1 Composition of seedless currant pomace
5.4.2 Impact of HTST-extrusion
5.4.3 Influence of planetary ball milling on particle size
5.4.4 Modified functionality after thermo-mechanical treatments
5.5 Application of intensively processed pomace in fat-based spreads
5.5.1 Wet ball milling in oil-suspension
5.5.2 Rheological properties and physical stability of sweet spreads
5.5.3 Sensory attributes of pomace spreads
5.6 Concepts for the implementation of zero-waste strategies
6 Conclusions
Bibliography
List of figures
List of tables
Appendix
List of publications
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:84741 |
| Date | 18 April 2023 |
| Creators | Reißner, Anne-Marie |
| Contributors | Rohm, Harald, Figiel, Adam, Jekle, Mario, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 10.1002/jsfa.9302, 10.3390/foods9111600, 10.1111/IJFS.15290, 10.1007/s00217-022-04052-5, 10.3390/foods12061315, info:eu-repo/grantAgreement/Bundesministerium für Bildung und Forschung via PTJ/FP7/031B0004//Adding value to fruit processing waste: innovative ways to incorporate fibres from berry pomace in baked and extruded cereal foods/Berrypom |
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