Tarımsal atıklardan protein üretiminin farklı yaklaşımlarla iyileştirilmesi
Improving protein production from agricultural waste through different approaches
- Tez No: 946225
- Danışmanlar: DOÇ. DR. DERYA KAHVECİ KARINCAOĞLU
- Tez Türü: Yüksek Lisans
- Konular: Gıda Mühendisliği, Food Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2025
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: Gıda Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Gıda Mühendisliği Bilim Dalı
- Sayfa Sayısı: 55
Özet
Proteinler, insan ve hayvan beslenmesinde temel makro besin ögeleri arasında yer almakta olup, yaşamın sürdürülmesi için elzemdir. Günümüzde artan nüfus, çevresel baskılar ve sürdürülebilirlik kaygıları, protein kaynaklarının yeniden değerlendirilmesini zorunlu kılmaktadır. Özellikle hayvansal protein kaynaklarının üretimi; yüksek maliyet, aşırı su ve enerji tüketimi, sera gazı salımı gibi çevresel olumsuzluklar nedeniyle eleştirilmekte ve alternatif protein kaynaklarına yönelim artmaktadır. Bu bağlamda, bitkisel protein kaynakları önemli bir potansiyele sahiptir. Yeşil yapraklı bitkiler, bu alternatifler arasında değerlendirilebilecek doğal ve çevre dostu kaynaklardır. Bununla birlikte, bazı sebzelerin üretim ve işleme aşamalarında yapraklarının doğrudan atık hâline gelmesi ve gıda olarak kullanılmaması, önemli bir protein kaynağının israf edilmesine yol açmaktadır. Bu çalışmada, karnabahar, brokoli, siyah havuç ve şeker pancarı yaprakları kullanılarak, çözünebilen proteinin yanı sıra soğuk sıkım sonrası posada kalan proteinin enzimatik işlem ile geri kazanılması ve aynı zamanda atık olarak kaybedilen bitki yapraklarının değerlendirilmesi hedeflenmektedir. Soğuk sıkım ile elde edilen posalara enzimatik işlem ve tekrar soğuk sıkım işlemi uygulanmıştır. Enzimatik işlem, iki farklı enzim türüyle (Alcalase® ve Celluclast®), 50 ℃, pH 5.5 ve 8'de, enzim dozu 5mg/g kuru madde, 24 saat ve 100 rpm olacak şekilde gerçekleştirilmiştir. Protein analizi için Kjeldahl yöntemi uygulanmıştır. Çalışmada yaprak, yeşil su, posa ve enzimatik işlem uygulanan tüm örneklerin protein analizleri yapılmıştır. Çalışmanın sonucunda, enzimlerin protein ekstraksiyonu üzerinde olumlu etkisi olduğu gözlemlenmiştir. Enzimatik işlem uygulanan örneklerden uygulanmayan örneklere göre daha fazla protein elde edilmiştir. Alcalase enzimi en verimli sonucu vermiştir. Alcalase enzimi ile verim %57'ye ulaşmıştır. Bu durumun Alcalase enziminin çalışma ortamından kaynaklandığı ögörülmektedir. Celluclast enzimi %44 ve tekrar sulu sıkma işlemi ortalama %5 oranında bir verim sağlamıştır. Ancak genel olarak, yapraklardaki toplam protein miktarına oranla posalardan geri kazanılan protein miktarlarının nispeten düşük kalması, bu yöntemin verimlilik açısından sınırlı olabileceğini göstermektedir. Bu yöntemin endüstriyel ölçekte uygulanabilirliğini artırmak amacıyla; verimin artırılmasına yönelik optimizasyon çalışmaları, enzim maliyetinin düşürülmesine yönelik stratejiler ve ön işleme adımlarının geliştirilmesi gibi konularda daha fazla bilimsel çalışmaya ihtiyaç duyulmaktadır. Yine de bu çalışma, sebze yapraklarının atık olarak değerlendirilmek yerine gıdaya dönüştürülmesinde önemli bir adım teşkil etmekte, sürdürülebilir protein üretimi için yenilikçi yaklaşımlar sunmaktadır.
Özet (Çeviri)
Proteins are fundamental macronutrients essential for maintaining life and ensuring the functional and structural integrity of living organisms. They play a critical role in supporting physiological activities and cellular repair mechanisms in both humans and animals. In recent years, the increasing world population, increasing environmental concerns associated with animal protein production, climate change, vegetarian and vegan diets and ethical concerns have increased the search for alternative protein sources. Moreover, the systems currently used to meet global meat demand are increasingly regarded as unsustainable due to their high energy and water consumption, extensive land use, and ecological burden. In this context, plant-based protein sources are gaining recognition for their potential to meet future protein demands more sustainably. Among the plant-based alternatives, soybeans, legumes, nuts, vegetables, and particularly green leafy plants have emerged as noteworthy options. Green leafy vegetables offer a renewable and affordable source of plant-based protein that is naturally abundant and underutilized. These leaves, often discarded during the harvesting and processing of vegetables such as broccoli, cauliflower, sugar beet, and black carrot, constitute a significant portion of agricultural waste. Valorizing these plant residues as protein sources not only mitigates food waste but also presents an opportunity to support the development of sustainable food systems. Furthermore, green leaves contribute positively to climate mitigation due to their carbon dioxide sequestration capabilities, positioning them as environmentally beneficial inputs in protein production. However, the structural characteristics of green leafy vegetables characterized by rigid, fibrous cellular matrices, pose a challenge to conventional protein extraction techniques. Many protein fractions remain entrapped within the insoluble plant matrix, particularly after juice extraction processes. To address this limitation, the present study focuses on enhancing protein recovery from post-press residues of cauliflower, broccoli, black carrot, and sugar beet leaves using enzyme-assisted extraction techniques. The goal is to improve protein yield and to assess the potential of these agricultural residues as valuable protein sources. Enzymatic extraction offers a number of advantages compared to traditional solvent-based or mechanical methods. By breaking down plant cell walls and increasing protein solubility through hydrolysis, enzymes can facilitate the release of proteins that are otherwise inaccessible. The enzymatic method is considered a green technology due to its relatively low energy input, reduced need for chemical solvents, and high extraction efficiency. Within the scope of this study, in the initial stage, the liquid phase was separated from the leaves using a cold pressing method; subsequently, two different methods were applied to the resulting pulp for protein analysis. In the aqueous pressing method, 50 grams of each pulp were weighed and diluted with 50 mL of distilled water at a 1:2 ratio. The prepared pulp-water mixtures were subjected to cold pressing again, thereby separating the liquid and solid phases. The liquid phase obtained was analyzed for protein recovery using the Kjeldahl method. In the enzymatic extraction method followed by aqueous pressing, 50 grams of pulp were weighed and diluted with 50 mL of distilled water and then homogenized. For protease application, Alcalase® 2.5L enzyme was used, and the pH of the samples was adjusted to 8. For carbohydrase application, Celluclast® enzyme was utilized, and the pH of the respective samples was adjusted to 5.5. The samples were placed in a water bath preheated to 50 °C, and once the target reaction temperature was reached, 250 mg of enzyme was added (corresponding to 5 mg/g dry matter). The enzymatic reaction was carried out for 24 hours at a shaking speed of 100 rpm. The Kjeldahl method was used to determine protein contents. Throughout the study, protein contents were analyzed in raw leaves, green juice, pulp, and all enzymatically treated fractions. Minitab (Minitab 16 statistics software) program was used for statistical analysis. Differences between samples were determined with ANOVA test at 95% confidence level. The effects of different enzymes on protein extraction were compared, and it was demonstrated that enzymatic treatments have the potential to enhance protein yield compared to conventional aqueous pressing methods. The results demonstrated that enzymatic treatments significantly enhanced protein extraction efficiency compared to untreated controls. Among the enzymes compared, Alcalase® exhibited superior performance, achieving protein recovery rates of up to 60% for cauliflower leaves pulp. This performance is largely attributed to Alcalase®'s optimal activity in alkaline conditions, where protein solubility is maximized, and cell wall disintegration is facilitated. In contrast, Celluclast®, which functions best in mildly acidic environments (pH 4.5–5.5), was less effective, likely due to the limited solubility of proteins near their isoelectric points under such conditions. Protein recovery varied across the different vegetable types. While cauliflower yielded the highest extraction efficiency, broccoli and black carrot also provided satisfactory results. Sugar beet leaves, on the other hand, yielded the lowest protein recovery regardless of the enzyme used. These results indicate that both the physiological structure of the leaf material and the type of pressing residue influence the effectiveness of protein extraction. Furthermore, this study investigated the effects of both the extraction method (enzymatic vs. aqueous cold pressing) and the type of plant residue on overall protein yield. Statistical analysis revealed that both factors significantly influenced the extraction efficiency, highlighting the importance of matrix characteristics and treatment selection in protein recovery processes. Despite the improvements achieved through enzymatic extraction, the amount of protein recovered remained modest relative to the total protein content initially present in the plant material. This observation underscores the need for further optimization if enzyme-assisted protein extraction from leafy vegetable residues is to be implemented at industrial scales. Future research should focus on refining process parameters—such as pH, temperature, enzyme dosage, extraction time, and agitation speed—to maximize protein recovery while preserving the functional properties of the extracted proteins. Studies from the literature confirm that alkaline conditions enhance protein solubility and facilitate efficient extraction. Increased temperature also plays a role by promoting enzyme activity and improving cell wall permeability. However, it is important to balance these parameters to avoid denaturation or degradation of valuable protein fractions. Therefore, optimization studies must aim not only to maximize yield but also to maintain protein integrity and nutritional quality. In addition to process optimization, combining different enzyme classes—such as cellulases, hemicellulases, and proteases—may lead to synergistic effects, further improving extraction outcomes. Moreover, pretreatment methods such as ultrasonication, mechanical grinding, or washing with organic solvents may help enhance enzyme accessibility to target proteins and thereby increase recovery rates. In conclusion, this study highlights the potential of green leafy vegetable residues as sustainable protein sources. Although current enzyme-assisted extraction techniques offer improvements over conventional methods, further development is necessary to fully exploit this potential at an industrial scale. Multidisciplinary efforts involving biochemical engineering, food technology, and environmental sciences will be essential to overcome current limitations. Integrating protein extraction from vegetable by-products into food production systems not only contributes to protein supply but also supports waste reduction and circular economy principles. Considering the accessibility and availability of such residues, valorization of these materials represents a strategic opportunity for sustainable food innovation.
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