Green-Chemical Nanofibrillated Cellulose from Pineapple Cores using Microfluidization

The production of nanofibrillated cellulose (NFC) from pineapple cores (Ananas comosus (L.) Merr.) involves green-chemical cellulose extraction followed by microfluidization. The chemical composition of pineapple cores was initially analyzed to assess their suitability for cellulose production. The analysis revealed that the pineapple cores contained 94.18 ± 0.20 % insoluble dietary fiber (IDF), while soluble dietary fiber (SDF) comprised only 0.31 ± 0.01 %, and consequently suitable for cellulose extraction. The cellulose extraction from pineapple cores involved removing non-cellulosic components: 1) Control (washed with water), under a green-chemical method with 0.1 M citric acid for 20 min at different temperatures, 2) Boiling (100 °C), and 3) Autoclaving (121 °C). Autoclaving with citric acid achieved the highest cellulose content (72.77 %), with minimal hemicellulose (21.44 %), lignin (13.33 %), galacturonic acid (3.42 %), and residual total sugar (1.82 %). The short extraction duration of only 20 min produces high-purity cellulose comparable to that obtained through alkaline and bleaching methods. Scanning electron microscopy (SEM) indicated that this method effectively removed non-cellulosic materials, increasing fiber porosity. The cellulose was then microfluidized at 25,000 psi (172 MPa) through 1 - 5 cycles, reducing the fiber diameters from 80.25 to 62.46 nm. Rheological testing revealed that NFC exhibited a higher storage modulus (G') than loss modulus (G''), suggesting gel-like behavior. NFC suspensions at 0.5 and 1 % concentrations showed viscosities of 3.35 - 3.85 cPs and 3.75 - 4.40 cPs, respectively. Therefore, NFC can function as a stabilizing agent for food without significantly altering the viscosity. HIGHLIGHTS Nanofibrillated cellulose (NFC) was efficiently extracted from pineapple cores using a green-chemical cellulose extraction method followed by microfluidization, offering an environmentally friendly alternative. Cellulose extraction via autoclaving with citric acid yielded the highest cellulose content (72.77 %) in a 1-step process and demonstrated superior purification efficiency. The rheological properties of NFC revealed gel-like behavior, indicating its potential as a stabilizing agent in food systems without significantly altering the viscosity. GRAPHICAL ABSTRACT