Investigating the cryoprotectant potential of nanocellulose valorized from pistachio hull and chestnut shell via innovative methods in bread dough frozen by different technologies

In this thesis study, it was aimed to produce nanocellulose cryoprotectants from pistachio hull and chestnut shell plant wastes, to evaluate the powder properties, and to determine the effects on the quality properties of fermented bread dough subjected to different industrial freezing techniques during storage. Temperature, processing time and solvent ratio, which are effective process parameters in nanocellulose production, were optimized using response surface methodology (RSM) and genetic algorithm (GA) techniques. Four different methods were used in the extractions: Conventional, microwave assisted, hydrotropic solvent and deep eutectic solvent. The produced nanocelluloses were added to the fermented bread dough, the samples were subjected to three different freezing techniques (static, air-blast and individual quick frozen; IQF), and the quality characteristics of the frozen product were examined during the six months of storage period. Optimization processes performed with GA for pistachio shell nanocellulose and with RSM for chestnut shell nanocellulose provided experimentally verifiable, high nanocellulose yields up to 99.2%, by using lower temperature, processing time and/or solvent ratios. Considering the yield and powder properties, deep eutectic solvent extraction was determined as the most suitable technique for the production of nanocellulose powders. Nanocellulose powders produced by green extraction methods had a fibrillated structure while after acid hydrolysis, crystal structure became dominant with varying crystallinity indexes in the range of 61.1% – 80.7%. The average diameters of the nanocellulose samples varied in the range of 1.26 – 279 nm. Air blast and IQF freezing processes caused small ice crystal formation inside and outside of the fermented bread dough, causing low damage to the microstructure. During the frozen storage period in all product groups, increases of up to 14.3% in total dry matter and up to 13.1 times in color difference values were observed. Compared to the control, the addition of nanocellulose to the dough formulation resulted in a reduction of up to 23.7% in α-amylase activity which fitted the second-order polynomial model. The use of nanocellulose has been effective in the preservation of quality parameters such as textural properties (16.2% – 22.0% lower bread firmness after six months of storage) and ion leakage (up to 22.9% reduction), and has provided positive effects in eliminating problems such as drip loss, which is among the main quality problems in the frozen food industry. It is determined that the use of nanocellulose, especially in combination with fast freezing techniques such as IQF, has the potential to provide significant advantages in terms of frozen food quality. As a result, it is thought that the production of innovative and high value-added nanocellulose cryoprotectant from domestic and industrial wastes, which occur as process waste in high quantities in our country, can provide benefits both economically, environmentally and technologically.