Optimization of olive leaves' thin layer, intermittent near-infrared-drying

Pyrka, Ioanna; Mantzouridou, Fani Th.; Nenadis, Nikolaos

doi:10.1016/j.ifset.2022.103264

Cited by 15 publications

(16 citation statements)

References 41 publications

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“…A statistically significant model was also found for CUPRAC assay, which is also based on an electron transfer mechanism, such as Folin Ciocalteu, indicating that the hydrolysis influences the redox properties of the rice hull extracts. A similar trend between the results obtained with Folin-Ciocalteu and CUPRAC assays has also been observed by Pyrka et al [25], where the authors suggested that drying affects the redox status of olive leaves. Temperature (X 2 ) and solvent:solid ratio (X 3 ) exhibited significant and positive linear and quadratic effects on CUPRAC response, whereas the duration of microwave treatment (X 1 ) exhibited a significant and positive quadratic effect.…”

Section: Model Fitting For Tpc a Dpph A Abts A Cuprac P-ca And Fasupporting

confidence: 88%

“…A statistically insignificant regression model was found for DPPH • scavenging activity. A lack of a statistically significant model for DPPH • has also been reported by Pyrka et al [25] who optimized olive leaves' thin layer using intermittent near-infrared-drying. The authors attributed this finding to synergistic and/or antagonistic phenomena of phenols that may occur upon testing the extracts [26], having as a consequence the minimization of differences in the estimated antioxidant activity, despite variations in their phenolic content.…”

Section: Model Fitting For Tpc a Dpph A Abts A Cuprac P-ca And Famentioning

confidence: 64%

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Recovery of Bound Phenolic Compounds from Rice Hulls via Microwave-Assisted Alkaline Hydrolysis

Kyriakoudi,

Misirli,

Mourtzinos

et al. 2023

Sustainability

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The present study aimed to optimize the recovery of bound phenolic antioxidants from rice hulls via microwave-assisted alkaline hydrolysis using response surface methodology. The microwave treatment duration, temperature, and solvent:solid ratio were the independent variables selected; whereas total phenol content, antioxidant activity (DPPH●, ABTS●+, CUPRAC assays), and the p-coumaric and ferulic acids concentration were the dependent ones. The optimum conditions were found to be 3.6 min, 155 °C, and 50:1 v/w which were then applied to hulls from different rice varieties cultivated in Greece [Gladio, Krezo, Scirocco, Karolina (two samples), Europa, Bravo, Bella (parboiled), and Fino (long-grain rice)]. The results were compared to those obtained using an optimized ultrasound-assisted alkaline hydrolysis protocol (120 min, 80 °C, 50:1 v/w) proposed in the literature. The values obtained with microwaves were much higher compared to those obtained by ultrasounds (i.e., p-coumaric acid levels were 1.2 to 2.2-fold higher, and those of ferulic acid were 2.1 to 6.0-fold higher) using almost 2-fold higher temperature but reducing the hydrolysis duration by ~33-fold. Thus, the optimized approach may assist the valorization of rice hulls as a sustainable source of natural phenolic antioxidants for novel food applications.

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Section: Model Fitting For Tpc a Dpph A Abts A Cuprac P-ca And Fasupporting

confidence: 88%

Section: Model Fitting For Tpc a Dpph A Abts A Cuprac P-ca And Famentioning

confidence: 64%

Recovery of Bound Phenolic Compounds from Rice Hulls via Microwave-Assisted Alkaline Hydrolysis

Kyriakoudi,

Misirli,

Mourtzinos

et al. 2023

Sustainability

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“…TPC was measured using the Folin-Ciocalteu colorimetric method [24]: Thus, 5 mL of deionised water were added to a 10 mL volumetric flask and mixed with an appropriate sample amount (0.1-0.5 mL) and 0,5 mL of Folin-Ciocalteu reagent. Exactly 3 min later, 1.5 mL of Na 2 CO 3 solution (20%) were added, and the mixture was diluted up to 10 mL with deionised water.…”

Section: Total Phenol Content (Tpc) Determinationmentioning

confidence: 99%

Exploring the Bioactive Content of Liquid Waste and Byproducts Produced by Two-Phase Olive Mills in Laconia (Greece): Is There a Prospect for Added-Value Applications?

Pyrka,

Koutra,

Siderakis

et al. 2023

Foods

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The use of a two-phase decanter (TwPD) for olive-oil extraction produces wastes and byproducts (a small volume of water from oil washing, olive leaves from the defoliator, and a high moisture pomace which can be destoned) that contain valuable bioactive compounds, such as phenolics and/or triterpenic acids. So far, there is no (water) or limited information (leaves and the destoned pomace fraction) on their content of bioactives, especially triterpenic acids. To contribute to the characterization of such streams from cultivars of international interest, in the present study, samples obtained from five mills from the region of Laconia (from one or two harvests) in Greece, where Koroneiki cv dominates, were screened for phenols and/or triterpenic acids. The leaves and pomace were dried at two temperatures (70 °C and/or 140 °C), and the pomace was also destoned before analysis. The liquid wastes contained low amounts of total (TPC) phenols (<140 mg gallic acid/L), hydroxytyrosol (<44 mg/L), and tyrosol (<33 mg/L). The olive leaves varied widely in TPC (12.8–57.4 mg gallic acid/g dry leaf) and oleuropein (0.4–56.8 mg/g dry leaf) but contained an appreciable amount of triterpenic acids, mainly oleanolic acid (~12.5–31 mg/g dry leaf, respectively). A higher drying temperature (140 vs. 70 °C) affected rather positively the TPC/oleuropein content, whereas triterpenic acids were unaffected. The destoned pomace TPC was 15.5–22.0 mg gallic acid/g dw, hydroxytyrosol 3.9–5.6 mg/g dw, and maslinic 5.5–19.3 mg/g dw. Drying at 140 °C preserved better its bioactive phenols, whereas triterpenic acids were not influenced. The present findings indicate that TwPD streams may have a prospect as a source of bioactives for added-value applications. Material handling, including drying conditions, may be critical but only for phenols.

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“…In recent years, some studies have investigated mint leaves drying using different methods and conditions of dehydration, IR drying (Ertekin & Heybeli, 2014), solar drying (Noori et al, 2021), microwave drying (Şimşek et al, 2021), microwave vacuum drying (Shankar & Natarajan, 2022), and freeze‐drying (Kovacı et al, 2022). Some scientific studies have also been conducted on IR drying of mint leaves (Mokhtarikhah et al, 2020), terebinth (Abbaspour‐Gilandeh et al, 2021), dill leaves (Tezcan et al, 2021), blueberries (Liu et al, 2022), crimson seedless grape (Matouk et al, 2022), sweet potatoes (Polat et al, 2022), carrot chips (Ochirov et al, 2021), red dragon (Bassey et al, 2022), and olive leaves (Pyrka et al, 2023). In all these studies, the drying power or temperature remains constant from the beginning to the end of the process.…”

Section: Introductionmentioning

confidence: 99%

Mentha spicata drying via infrared: Mathematical modeling and evaluation of two‐step temperature potential for improving drying characteristics

Hazervazifeh,

A. Moghaddam

2024

J Food Process Engineering

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To assess the effects of a two‐step temperature method (TTM) on dehydration parameters, color deterioration of dried samples, and specific energy consumption (SEC), spearmint leaves were dried using infrared (IR) undergoing the TTM. Moreover, 14 mathematical models were compared based on the adjusted correlation coefficient, reduced chi‐square, and root mean square error to estimate drying curves. Changes in the color of the dried product at two‐step temperatures of 70to60°C, 60to50°C, and 50to40°C led to decreases of 2.69, .81, and 3.34 compared to fixed temperatures of 70, 60, and 50°C, respectively. On the other hand, the specific energy consumption (SEC) increased by 5.43, 10.92, and 22 MJ.g−1 H2O at 70to60°C, 60to50°C, and 50to40°C compared to 70, 60, and 50°C, respectively. To interpret the results from another point of view, three basic objectives of shortening drying time, reducing energy consumption, and raising the quality of the dried product are achieved in the TTM. For instance, the drying time and energy consumption are reduced at a two‐step temperature of 70to60°C compared to the fixed temperature of 60°C, along with a decrease in the color change compared to the fixed temperature of 70°C. The results indicated that Midilli et al. model resulted in the best fitness in explaining the IR drying behavior of spearmint leaves.Practical applicationsDuring the falling rate period in drying process and especially at higher temperatures and powers, there is a potential for a decrease in the quality of the dried product, and even the risk of thermal runaway due to excessive temperature increase. Certainly, at lower powers and temperatures, the quality of the dried product can be enhanced. However, in this situation, the duration of the process and the energy consumed, which are two crucial factors in the drying process, increase, leading to financial losses for the producer. In the two‐step temperature method (TTM), due to the temperature reduction during the critical period of falling rate, the quality of the dried product improves by considering the processing time and energy consumption.

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Optimization of olive leaves' thin layer, intermittent near-infrared-drying

Cited by 15 publications

References 41 publications

Recovery of Bound Phenolic Compounds from Rice Hulls via Microwave-Assisted Alkaline Hydrolysis

Recovery of Bound Phenolic Compounds from Rice Hulls via Microwave-Assisted Alkaline Hydrolysis

Exploring the Bioactive Content of Liquid Waste and Byproducts Produced by Two-Phase Olive Mills in Laconia (Greece): Is There a Prospect for Added-Value Applications?

Mentha spicata drying via infrared: Mathematical modeling and evaluation of two‐step temperature potential for improving drying characteristics

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