تاثیر روش‌های مختلف استخراج بر ویژگی‌های فیبر حاصل از پودر تفاله زیتون چربی‌زدایی شده

هدف از پژوهش حاضر مقایسه تاثیر روش‌های استخراج سبز (آنزیمی و فراصوت) و متداول (شیمیایی به کمک حلال اسیدی و قلیایی) بر بازدهی (فیبر رژیمی کل(tdf)، فیبر محلول (sdf) و فیبر نامحلول(idf))، ترکیب شیمیایی و خواص آبپوشی فیبر تفاله زیتون بود. خواص رئولوژیکی خمیرهای حاوی مقادیر مختلف sdf (0، 5، 10 و 15 درصد) نیز مورد بررسی قرار گرفت. بازده فیبر کل بین 74.79 (روش فراصوت) تا 90.2 % (روش آنزیمی) بود که 12.12 – 21.68 % آن sdf بود. میزان رطوبت sdf بیشتر از idf بود. محتوای خاکستر و پروتئین idf بیشتر از sdf بود. روش استخراج تاثیر معنی‌داری بر میزان رطوبت و خاکستر sdf نداشت. کمترین میزان پروتئین در df استخراج شده به روش آنزیمی مشاهده شد. بیشترین و کمترین قدرت تورم و شاخص حلالیت به ترتیب برای فیبر استخراج شده به روش آنزیمی و فراصوت بود که ناشی از میزان جذب آب این فیبرها بود. غنی‌سازی آرد گندم با sdf استخراج‌شده به روش آنزیمی نشان داد که افزودن 10 درصد فیبر موجب افزایش زمان توسعه و پایداری و fqn خمیر می‌شود در حالی که درجه نرم شدن را کاهش می‌دهد (p<0/05). جایگزینی 15 درصد آرد گندم با sdf منجر به افزایش مقاومت به کشش و انرژی خمیر شد. کشش‌پذیری خمیر با افزودن 5 درصد فیبر افزایش یافت، در حالی که افزودن 10 درصد فیبر این شاخص را به کمتر از مقدار شاهد رساند. در مجموع، اگرچه عملکرد روش آنزیمی به طور قابل توجهی بالاتر از سایر روش‌ها بود، اما این روش زمان‌بر است که کاربردی آن در صنایع غذا را محدود می‌کند. به‌کارگیری ترکیبی از روش‌های سبز برای تسریع استخراج آنزیمی می‌تواند موضوعی برای پژوهش‌های آینده باشد. بعلاوه، جایگزینی 10% آرد گندم با sdf خواص رئولوژیکی قابل قبولی را ارائه می‌دهد که می‌تواند نویدبخش نانی با کیفیت و با ارزش غذایی بالا باشد.

effects of different extraction methods on physicochemical properties of dietary fiber from defatted olive (olea europaea) pomace flour

introduction: in the food industry, various fruits and vegetables are processed to produce value-added products. large proportions of waste resulting from these processes can cause a lot of environmental pollution. moreover, these residues are a rich source of valuable bioactive compounds and dietary fiber and efficient use of them is important for both nutritional and environmental reasons. the olive oil process produces a solid residue called olive pomace. olive pomace has a high antioxidant capacity and is rich in dietary fiber (df), oil, and polyphenolic compounds. however, the soluble fiber level of the pomace is low and limits the use of this fiber. therefore, converting insoluble fiber to soluble can improve its health benefits and functional properties. fiber extraction conditions can lead to changes in the proportion and concentration of the soluble and insoluble fiber, as well as the physicochemical and nutritional characteristics of these compounds. chemical extraction (by acidic and alkaline solvents) is the most common method for fiber extraction. damage to the fiber structure can occur as a result of the harsh conditions during chemical extraction (temperature, process time, and ph). in addition, these methods lead to environmental pollution. therefore, green extraction methods have received great attention. thus, the current research aims to compare the effect of green (enzyme- and ultrasound-assisted extraction) and conventional (by acidic and alkaline solvents) extraction methods on the yield, chemical composition, purity, and hydration properties of the dietary fibers obtained from olive oil pomace flour. furthermore, by replacing wheat flour with different amounts (0, 5, 10, and 15%) of the soluble fiber obtained from the most appropriate method, the rheological (i.e., farinograph and extensograph) properties of the resulting dough are also estimated. materials and methods: the olive pomace was obtained from biomass residue of the olive oil process which was defatted using the soxhlet method. this olive pomace was dried in an oven at 50 ºc until reaching a moisture content of around 10%. the dried sample was grounded and kept in a dark bottle at 4 ºc until the fiber extraction process. fiber extraction was done based on the acid solvent- (citric acid: pomace = 40: 1; 2 hours; 40 ºc); alkaline solvent- (1% naoh: flour = 40: 1; 2 hours; 40 ºc); ultrasonic- (0.5% naoh: flour = 40:1; 1 hour; 40 ºc; w 400) and enzyme- (α-amylase; protease; amyloglucosidase; cellulase; 4.5 hours; 40 ºc) assisted method. then soluble and insoluble fiber was separated. extraction yield, chemical composition (moisture, ash, protein, soluble and insoluble fiber), water holding capacity, swelling power, and solubility index of soluble and insoluble fiber were compared. the effect of supplementation of wheat flour with different amounts of soluble olive pome fiber (0, 5, 10, and 15%) on farinographic (water absorption rate (%), dough development time (min), stability time (min), softening degree (bu) and flourgraph quality number) and extensograph (resistance to extension (bu); extensibility (mm), energy (cm2) and rate number; at three resting time: 45, 90 and 135 minutes) properties of doughs were evaluated. experiments were performed in three replicates and data were reported as mean ± standard deviation. collected data were subjected to a one-way analysis of variance using a random factorial experimental design. the significant difference between the means was determined by tukey’s test at p < 0.05. results and discussion: the yield of olive pomace fiber was 74.79 -90.2 % which 12.12 -21.68 % of them was soluble fiber. the lowest and highest tdf yield was recorded for ultrasound and enzyme-assisted methods, respectively (p < 0.05). the acidic and alkaline conditions can lead to the hydrolysis of fiber into oligosaccharides and monosaccharides, which reduces the fiber yield. the yield of the alkaline method was more than the acidic one (p < 0.05). while there was no significant difference between the yield of idf of acid (64.99%) and the alkaline (64.67%) method, the sdf yield of the alkaline method (16.45%) was significantly higher than the acidic (60.60%) one. the moisture content of sdf was more than that evaluated for idf. the ash and protein contents of idf were higher than sdf. in the idf, the lowest moisture content was reported for the ultrasound method (p < 0.05). in the sdf, there was no significant difference between the moisture content of fibers extracted by different methods (p > 0.05). the extraction method had no significant effect on the ash content (p < 0.05). the lowest protein content was observed in the fiber extracted by the enzymic method (p < 0.05). moreover, the sdf was purer than the idf and the extraction method had no significant effect on the fiber purity. the water holding capacity of the sdf (7.68 to 11.43 g g-1) was higher than the idf (2.09 to 2.81 g g-1). swelling power, solubility index and water holding capacity of olive pomace fiber showed a positive and significant correlation with each other. the higher swelling power and solubility index was obtained for the fiber extracted by the enzymic method due to the higher water absorption of this fiber. the lowest water holding capacity, solubility, and swelling power were obtained for samples extracted by the ultrasound-assisted method. the investigation of rheological properties of doughs enrichment with soluble fiber extracted by enzymatic method showed that the water absorption rate increased from 63.73 to 68.63 (p < 0.05) by increasing the fiber portion in the doughs. moreover, by increasing the fiber level to 10%, the dough development time, stability time and fqn increased, but no significant effect was observed in higher fiber content. however, by increasing the fiber content, the doftening degree decreased significantly. replacing flour with 15% fiber led to increasing resistance to the extension of doughs at a resting time of 45 minutes. while there was no significant difference between the samples at the resting times of 90 and 135 minutes. at the resting time of 45 minutes, the extensibility of the dough increased significantly with the addition of 5% fiber, while the addition of 10% fiber reduced this index to less than the control value. at the resting time of 135 minutes, the extensibility of the sample containing 15% fiber was significantly lower than others. at the resting time of 45 and 135 minutes, adding 15% fiber caused a significant increase in energy index (p < 0.05). conclusions: although the performance of the enzymatic method was significantly higher than other ones, this method was very time-consuming which limits its application in the food industry. the use of a combination of two or more green methods to accelerate the speed of extraction can be a topic for future research. furthermore, the replacement of 10 % of wheat flour with olive soluble fiber obtained by the enzymatic method also showed acceptable rheological properties. this dough can meet the expectation for high-quality bread with higher nutritional value. further research is needed to optimize the formulation of dough bread for using more fiber, to investigate the effect of total dietry fiber of olive pomace extracted by different methods on the nutritional and functional properties of food, and to establish low-fat and free gluten formulation based on olive pomace fiber.