The purpose of this study was to introduce a new source of antioxidants obtained from grape pomace as well as aronia and blueberry and engages them in preparation of a new yoghurt product in order to be last – longer and more beneficial for human health than the traditional one. Totally, grape pomaces from 4 varieties (Zupjanka, Prokupec, Kadinal and Vranec), as well as blueberry and aronia, were used. For the extraction of polyphenolics, liquid-liquid extraction with ethanol/water/acetic acid was used, followed by roto-evaporation, in order to concentrate the extracts and then to introduce them into the milk. The total phenolic content of the extracts was determined by the Folin-Ciocalteu method and the total anthocyanins were analyzed by dilution of the samples with ethanol/water/HCl, obtaining three different volumes of extracts (10, 50 and 100 mL) of each sample (grape pomaces, blueberry and aronia), obtaining 36 extracts in total. The three different concentrates of each sample (18 in total) were applied on milk together with the lactic bacteria in order to study the influence of polyphenolics during the fermentation; as well as, 18 other extracts applied on milk after the fermentation (into the obtained yoghurt). The pH value of the newly generated yoghurts was analyzed during the fermentation and storage.
The aronia sample presented highest phenolic content (431 mg/L), while Zupjanka had the lowest content of polyphenols (67.9 mg/L). The grape pomace presenting best results was Prokupec (246 mg/L). All yoghurt samples containing polyphenolics applied before the fermentation, presented higher pH value compared to the control and samples with polyphenolics applied after fermentation. Furthermore, all yoghurt samples containing phenolics extract with highest concentration, showed best results, presenting stable pH value. Sensory analysis was performed on the different yoghurt samples, concluding that the new products have creamy texture, good taste, without unpleasant smell or bitterness. The colour of some samples turned into red-violet, excluding the yoghurt with extracts from: Zupjanka and Kardinal. By microbiological analysis the presence of pathogen and other harmful bacterias was proved to be negative, showing that this yoghurt is a main basis for manufacturing of a more beneficial dairy product that could be soon available on the market.
Table of Contents
1. INTRODUCTION
1.1 Grape pomace
1.2 Polyphenols
1.3 Yoghurt
1.4 Biofuel
2. EXPERIMENTAL (PART I)
2.1 Samples
2.2 Extraction of phenolic compounds from samples
2.3 Determination of total polyphenols
2.4 Determination of total anthocyanins
2.5 Concentration of extracts with rotoevaporation
2.6 Application of phenolic dry extracts in milk during fermentation
2.7 Application of phenolic dry extracts after fermentation i.e. in yoghurt
2.8 pH – Measurement of the new yoghurt
3. RESULTS (PART I)
3.1 Spectrophotometric analysis
3.2 pH variation of the obtained yoghurt
3.3 Sensory analysis of the new product
3.4 Microbiological analysis of the new yoghurt products
4. EXPERIMENTAL (PART II)
4.1. Production of biodiesel from grape winery waste and fruit peels
5. RESULTS (PART II)
6. DISCUSSION
7. CONCLUSION
8. REFERENCES
Research Objectives and Core Themes
The research investigates the sustainable utilization of grape pomace, a winemaking waste product, for two primary applications: as a natural source of antioxidants to enrich yoghurt and as a renewable feedstock for biodiesel production. The central research question explores whether these waste materials can effectively improve the nutritional profile and shelf-life of dairy products while simultaneously providing a cost-effective, environmentally friendly alternative to fossil fuels.
- Extraction and analysis of phenolic compounds from different grape pomace varieties and berries.
- Development of novel yoghurt products enriched with antioxidants to evaluate pH stability and organoleptic properties.
- Assessment of the antioxidant potential and microbiological safety of the modified yoghurt samples.
- Evaluation of various organic solvents for oil extraction from grape seeds and peels for biodiesel synthesis.
- Comparison of extraction yields and fuel potential of different pomace-derived oils.
Excerpt from the Book
1.1 Grape pomace
Grape pomace stands for the solid remains of grapes (skins, stalks and seeds), which are being discarded during winemaking (after grapes are pressed). The largest fraction of winery waste is pomace (Figure 1) which is thrown away ending up in landfills. Fruit processing industries generate tremendous amount of solid wastes which is almost 35-40% dry weight of the total produce used for the manufacturing of juices. During the management of these wastes there is a production of greenhouse gases (GHG) which must be taken into account. Winery leftovers pile up fast and can cause some serious environmental problems if not disposed properly.
Summary of Chapters
1. INTRODUCTION: Provides an overview of the wine industry waste in Macedonia and the potential of grape pomace as a functional resource for antioxidants and biofuels.
2. EXPERIMENTAL (PART I): Details the methodological approach for extracting polyphenols from six samples and the experimental procedures for creating and testing antioxidant-enriched yoghurts.
3. RESULTS (PART I): Presents the spectrophotometric data, pH monitoring during storage, sensory evaluations, and microbiological testing results for the new yoghurt formulations.
4. EXPERIMENTAL (PART II): Describes the chemical procedures for oil extraction from seeds and fruit peels, followed by transesterification to produce and test biodiesel.
5. RESULTS (PART II): Summarizes the experimental yields of oil and impure biodiesel obtained using different organic solvents across various samples.
6. DISCUSSION: Interprets the findings regarding the impact of polyphenols on yoghurt preservation and evaluates the feasibility of converting winemaking waste into biodiesel.
7. CONCLUSION: Synthesizes the project outcomes, confirming the viability of using grape pomace to enhance food quality and produce sustainable fuel, while suggesting future research directions.
8. REFERENCES: Lists the academic literature and technical resources consulted throughout the study.
Keywords
Grape pomace, Winemaking waste, Polyphenols, Antioxidants, Yoghurt, Fermentation, Biodiesel, Transesterification, Renewable energy, Food preservation, Functional foods, Phenolic content, Anthocyanins, Sustainable development, Waste management.
Frequently Asked Questions
What is the primary scope of this research?
This research evaluates the dual-purpose utilization of grape pomace—a significant winemaking byproduct—specifically for enriching yoghurt with natural antioxidants and as a feedstock for producing renewable biodiesel.
What are the main research themes?
The core themes include sustainable waste management, food science and nutritional enhancement, and the chemistry of renewable energy production from agricultural byproducts.
What is the central research question?
The study asks whether winemaking waste (grape pomace) can be repurposed into value-added products, such as stable functional yoghurts and sustainable biofuels, to mitigate environmental impact and resolve energy scarcity.
Which scientific methodologies were employed?
The study used liquid-liquid extraction for polyphenols, the Folin-Ciocalteu method for quantification, spectrophotometry, pH monitoring of fermentation processes, sensory analysis, microbiological safety testing, and transesterification for biodiesel synthesis.
What does the main body of the work cover?
It covers the extraction of compounds, the creation and storage testing of antioxidant-enriched yoghurts, the oil extraction from seeds/peels, and the experimental conversion of these oils into biodiesel using different solvent configurations.
Which keywords best characterize this work?
Key terms include grape pomace, antioxidants, functional yoghurt, biofuel, transesterification, and waste recycling.
How did the addition of polyphenols affect the yoghurt?
The addition of polyphenols was found to improve the pH stability of the yoghurt during storage and did not negatively impact the creamy texture or taste, while protecting against spoilage.
What were the findings regarding biodiesel production?
The study found that acetic acid was an effective solvent for oil extraction, and that grape seeds and fruit peels are viable, cost-effective sources for biodiesel, demonstrating high potential for future sustainable energy applications.
- Citation du texte
- Violeta Ivanova-Petropulos (Auteur), Zorana Andonovic (Auteur), Dusko Nedelkovski (Auteur), Krste Tasev (Auteur), Klime Beleski (Auteur), 2014, Application of Grape Pomace as a Natural Food Preservative and Source of Biofuel, Munich, GRIN Verlag, https://www.grin.com/document/276447
