The impact of drying techniques on phenolic compound, total phenolic content and antioxidant capacity of oat flour tarhana

Acerola processing waste: Convective drying with ethanol as pretreatment

The acerola seed is an agro-industrial waste. It is a high moisture content product, rich in bioactive compounds. Drying is an alternative to make this waste available in a safe condition. The use of ethanol as a pretreatment could improve the drying process besides reducing the operation time. This study aimed to investigate the influence of ethanol pretreatment (ET) on the content of bioactive compounds, cell wall thickness, and color. The drying kinetics was studied, and the influence of external and internal resistance was discussed. The samples were immersed in ethanol for 2 min with subsequent convective drying (40 °C and 60 °C; 1 m s-1) until they reached the equilibrium condition. The ET reduced the drying time up to 36.36 %. The external and mixed control of mass transfer were identified as the governing regimes for drying this material, depending on the use of ethanol. ET led to an increase in effective diffusivity, a reduction in cell wall thickness, and preservation of the color of the dried waste. The ET positively impacted the conservation of ascorbic acid compared to untreated dried samples but was not relevant to phenolic compounds, carotenoids, and antioxidant activity. The drying process increased the bioactivity of the anthocyanins. The best condition was drying at 60 °C, pretreated with ethanol.

Effect of fermentation on the antioxidant properties and phenolic compounds of Bambangan (Mangifera pajang) fruit

The study aimed to determine the antioxidant activities and phenolic compounds of Bambangan (Mangifera pajang), a type of wild fruit belongs to the family of Anacardiaceae during fermentation at room (28 °C) and elevated temperature (35 °C). The antioxidant capacity was estimated based on 2,2-diphenyl-1-picyrlhydrazyl (DPPH) scavenging activity, ferric-ion-reducing power (FRAP), 2,2´-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation assay and oxygen-radical absorbing capacity (ORAC). A reversed phase high performance liquid chromatography (HPLC) was used to identify the phenolic compounds. Samples of bambangan fermented at 35 °C achieved the highest FRAP (141.42 mM Fe(II)/g extract) and ABTS values (5.00 mmol TE/g) within the first six days as compared to the samples fermented at room temperature (28 °C), which required 10 days to achieve the highest FRAP and ABTS values. No significant difference was found (p > 0.05) on the antioxidant activity of the samples that were kept at prolonged fermentation and storage. The total phenolic content (TPC) increased throughout the fermentation with the highest value of 44.69 ± 0.01 mg GAE/g. Gallic acid, chlorogenic acid, vanillin, ρ -coumaric acid and rutin are the major phenolic compounds identified in the fermented product. The results suggested that the antioxidant capacity of bambangan is affected by the fermentation temperature and the fermented product could be a source of antioxidants.

Phenolic compounds in walnut pellicle improve walnut (Juglans regia L.) protein solubility under pH-shifting condition

This study focused on the interaction of walnut protein with phenolic extracts of walnut pellicle (PEWP) under alkaline condition, leading to enhancement of protein solubility under neutral condition. First, the change of PEWP under alkaline condition was determined by RP-HPLC and mass spectrometry, and the results showed that most ellagitannins in PEWP could be retained under alkaline condition within 3 h. Interaction between PEWP and walnut protein under pH-shifting condition resulted in the remarkable increase of protein solubility (above 90%) at neutral pH. The results from SDS-PAGE and SEC showed that the improved solubility lied in the formation of large and soluble protein aggregates due to the covalent interaction among walnut protein and polyphenols. A significant change in tertiary structure of protein-phenolic complex was witnessed by fluorescence spectrum and near-UV circular dichroism. Meanwhile, walnut protein-polyphenol interaction led to a slight increase in β-turn while a slight decrease in β-sheet. Combined with amino acid composition, it could be illustrated that the covalent bonding for walnut protein with polyphenol mainly occurred at Lysine residues.

Quinoa Snack Production at an Industrial Level: Effect of Extrusion and Baking on Digestibility, Bioactive, Rheological, and Physical Properties

This research aimed to produce gluten-free snacks on a pilot scale from quinoa flour. These snacks experienced an extrusion process, followed by baking. The effects of these technological processes on carbohydrate and protein digestibility, extractable phenolic compounds (EPP), hydrolyzable phenolic compounds (HPP), antioxidant capacity, and physical properties were evaluated in raw quinoa flour and extruded snacks. Extrusion increased digestible starch (RDS) from 7.33 g/100 g bs to 77.33 g /100 g bs. Resistant starch (RS) showed a variation of 2 g/100 g bs. It is noteworthy that protein digestibility increased up to 94.58 g/100 bs after extrusion and baking. These processes increased HPP content, while EPP and carotenoid content decreased. The samples showed significant differences (p < 0.05) in the antioxidant properties determined through the DPPH and ABTS methods. Values of 19.72 ± 0.81 µmol T/g were observed in snacks and 13.16 ± 0.2 µmol T/g in raw flour, but a reduction of up to 16.10 ± 0.68 µmol T/g was observed during baking. The baking process reduced the work of crispness (Wcr) from 0.79 to 0.23 N.mm, while the saturation (C*) was higher in baked ones, showing higher color intensity. The baking process did not influence the viscosity profile. The results in this study respond to the growing interest of the food industry to satisfy consumer demand for new, healthy, and expanded gluten-free snacks with bioactive compounds.

Effects of cutting and drying method (vacuum freezing, catalytic infrared, and hot air drying) on rehydration kinetics and physicochemical characteristics of ginger (Zingiber officinale Roscoe)

The purpose of this study was to discuss the effects of cutting methods (transverse cutting [TC] and longitudinal cutting [LC]) and drying methods (vacuum freeze-drying [FD], hot air drying [HD], catalytic infrared drying [CID]) on rehydration kinetics and physical and chemical characteristics of rehydrated ginger. The research results showed that the rehydration rate and equilibrium moisture content increased with an increase in temperature. LC samples had a higher rehydration rate, while TC samples showed higher equilibrium moisture. Peleg model can fit the rehydration curve of the sample well. The highest coefficient of determination (R2 ) was 0.99, while the sum of squares error and lowest chi-square (χ2 ) was close to zero. Compared with fresh samples, the rehydrated ginger slices had lower gingerol content, total phenol content (TPC), total flavonoid content (TFC), and higher antioxidant activity. The different cutting methods had no significant effect on the physical and chemical properties of rehydrated ginger. In conclusion, TC-CID rehydrated products have better retention of gingerol, TPC, TFC, and antioxidant properties, which was similar to the principal component analysis. PRACTICAL APPLICATION: The results of this study show that transverse cutting combined with catalytic infrared drying is a unique processing technology. Due to the short xylem of transverse cutting ginger, the xylem diameter can be restored during rehydration, the balanced water content was high, and the quality of dried ginger can be restored to the greatest extent. This makes food processors competitive in the operation process and provides better services to consumers.

Possibility of Pulsed Electric Field and Essential Oil Pre-treatment, Microwave-air Dehydration to the Quality of the Dehydrated Sesban (Sesbania sesban) Flower

Non-heat ahead-treatment in advance of the main dehydration is essential to preserve the quality and ensure food safety. Pulsed electric field (PEF) utilizes a high-voltage electric field in a very short duration to inhibit microbes and enzymes while maintaining the most sensory and nutritional characteristics. For thermal sensitive components, the dehydration process should be performed at low temperatures. Freeze dehydration, vacuum dehydration required high cost for equipment, energy consumption, low quantity in long dehydration time. Microwave-air dehydration is considered as a promising alternative technical approach. Sesban (Sesbania sesban) flower contains numerous phytochemical components promoting health-benefit. However, it’s highly perishable after harvesting. Consumers enjoy the dried sesban flower as a healthy drink. This study examined the possibility of PEF ahead-treatment in microbial inhibition and enzymatic inactivation; essential oil and Microwave-air dehydration on retention of total phenolic content (TPC), vitamin C, 2,2 diphenyl-1-picrylhydrazyl of free radical scavenging (DPPH), ferric reducing antioxidant power (FRAP) of the dehydrated sesban flower. Research also monitored the microbial stability of the dehydrated sesban flower during 12 months of preservation. Results showed that PEF at pulse strength 1000 kV/cm, pulse duration 90 µs, pulse number 45 was remarkably inactivated polyphenol oxidase and peroxidase in raw material. Rosemary essential oil soaked for sesban flower before dehydration positively preserved the ascorbic acid, phenolic content and antioxidant capacity. These PEF and essential oil ahead-treatments strongly facilitated for the main Microwave-air dehydration. Among different air temperatures from 20°C to 40°C in microwave-air dehydration, the highest Vitamin C, TPC, DPPH and FRAP of the dried flower were recorded at air temperature from 20°C to 30°C with no significant difference. Meanwhile, airspeed 1.2 m/s showed the highest Vitamin C, TPC, DPPH and FRAP of the dried flower with no significant difference with airspeed 1.4 m/s and 1.6 m/s. There was no significant difference in Vitamin C, TPC, DPPH and FRAP of the dried flower by microwave power from 1.15 to 1.45W/g. Therefore, a combination of microwave and air dehydration at air temperature 25°C, airspeed 1.2 m/s, the microwave energy density of 1.45 W/g was recommended to better preserve vitamin C, TPC, DPPH, FRAP. Microbial stability of the dehydrated flower was also observed during 12 months of storage by 3 month-interval sampling. Coliform, yeast and mold criteria in dried product were stable within acceptable limits.

Influence of pomegranate seed extract on the formation of biogenic amines in a cereal based fermented food: Tarhana

In this research, biogenic amine content, acidity, pH values, total free amino acid content (TFAA), ash content, colour values (CIE L*, a*, b*), total phenolic compound content (TPCC) and antioxidant activity values of tarhana, which were fortified with pomegranate seed extract (PSE) in different ratios (0%, 0.5%, 1%, 2%) were evaluated during six months of storage. It has been evaluated that pomegranate seed extract causes increase on TPCC, ash content and antioxidant activity values. Putrescine, cadaverine, spermidine, spermine, histamine, tyramine were studied as biogenic amines. Standard addition and internal standard techniques were performed for quantification of biogenic amines. Recovery rates were found between 87.0% and 94.6%. Total biogenic amine contents of tarhana samples decreased during the first two months of storage, remained constant and increased slightly for the next four months. It was found that, pomegranate seed extract causes decrease on biogenic amine content of tarhana samples. While the average total biogenic amine content in control group was 894.70 mg/kg, tarhana samples which were fortified with pomegranate seed extracts in ratios of 0.5%, 1%, 2% contained 569.67 mg/kg, 514.52 mg/kg, 424.60 mg/kg total biogenic amine, respectively.

Effects of Freeze Vacuum Drying Combined with Hot Air Drying on the Sensory Quality, Active Components, Moisture Mobility, Odors, and Microstructure of Kiwifruits

In this study, freeze vacuum drying (FVD), hot air drying (AD), and FVD combined with AD (FVD-AD) were used to dry kiwifruits. Dried products were analyzed comprehensively on their sensory quality, active components, moisture mobility, odors, and microstructure. Results showed that the FVD-AD saved time by 38.22% compared with FVD while maintaining an acceptable product quality. The antioxidant properties of FVD-AD were lower than those of FVD but significantly higher than those of AD. Moreover, compared with FVD products, FVD-AD products were moderately hard (5252.71 ± 33.53 g) and improved in color, bound water, and microstructure. Additionally, FVD-AD consumed lesser drying time and energy than FD. According to cluster analysis, the odors of FVD-AD products were similar to those of the fresh ones. Principal component analysis of physicochemical and drying cost indicated that FVD-AD was a promising processing technique for functional kiwifruit snacks.

Nutritional quality of heat-sensitive food materials in intermittent microwave convective drying

Background

The retention of health promoting components in nutrient-rich dried food is significantly affected by the dehydration method. Theoretical and experimental investigations reported in the literature have demonstrated that intermittent microwave convective drying (IMCD) can effectively improve the drying performance. However, the impact of this advanced drying method on the quality food has not been adequately investigated.

Design

A programmable NN-SD691S Panasonic inverter microwave oven (1100 W, 2450 MHz) was employed for the experiments. The microwave power level was set at 100 W and ran for 20 seconds at different power ratios and the constant hot air conditions was set to a temperature of 60°C and 0.86 m/s air velocity.

Objective

In this study, natural bioactive compounds (ascorbic acid and total polyphenol), water activity, colour and microstructure modifications which can occur in IMCD were investigated, taking kiwifruit as a sample.

Results and Discussion

The microwave (MW) power ratio (PR) had significant impact on different quality attributes of dried samples. The results demonstrate that applying optimum level MW power and intermittency could be an appropriate strategy to significantly improve the preservation of nutrient contents, microstructure and colour of the dried sample. The IMCD at PR 1:4 was found to be the ideal drying condition with the highest ascorbic acid retention (3.944 mg/g DM), lowest colour change (ΔERGB = 43.86) and a porous microstructure. However, the total polyphenol content was better maintained (3.701 mg GAE/g DM) at higher microwave density (PR 1:3). All samples attained a desirable level of water activity which is unsusceptible for microorganism growth and reproduction.

Conclusion

Overall, IMCD significantly improved the drying performance and product quality compared to traditional convective drying.

Microbiological and chemical properties of wet tarhana produced by different dairy products

This study investigated the use of kefir, yogurt and their combination in the production of wet tarhana with an aim to increase the nutritional value of the end product. Along with microbiological and chemical properties, the volatile compound composition of wet tarhana was also evaluated. Wet tarhana revealed an increase in the lactic acid bacteria count (LAB) with the addition of kefir. After fermentation, counts of total yeast, LAB, and total mesophilic aerobic bacteria were 7.57, 8.26 and 7.64 log CFU/g, respectively. The values of pH and titratable acidity were measured as 4.78 and 4.68% in terms of lactic acid, respectively, at the end of fermentation. Lactic acid content increased from 3.31 to 10.82 g/kg throughout fermentation. A total of 72 volatile compounds were recorded during fermentation and 44 of these were identified by GC-MS. The most abundant compounds identified in the tarhana samples were hexadecanoic acid and 9,12-octadecadienoic acid. Moreover, ABTS antioxidant activity results of all formulations were measured in the range of 15.86 and 19.31 µmol TE/g at the end of fermentation and it was independent of the fermentation period.

Thermal inactivation kinetics and effects of drying methods on the phenolic profile and antioxidant activities of chicory (Cichorium intybus L.) leaves

The thermal inactivation kinetics of enzymes, including polyphenol oxidase (PPO) and peroxidase (POD), in chicory (Cichorium intybus L.) leaves were evaluated. In addition, the influences of different drying techniques (shade drying, hot air drying and freeze drying) on the phenolic profiles and antioxidant activities of chicory leaves were determined. The antioxidant activities of chicory leaves were evaluated on the basis of their 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, reducing power, and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity. The results showed that the activation energy for PPO and POD inactivation were 123.00 kJ/mol and 78.99 kJ/mol, respectively. Preliminary treatment with hot water for 3 min at 90 °C was beneficial for preserving the phenolics present in fresh leaves. Hot air drying was better for the phenolics preservation. The hot air-dried and freeze-dried leaves possessed good antioxidant activities. The leaves with higher phenolics contents had better antioxidant activities, which indicated that the preservation of the phenolics was important for maintaining the antioxidant activity of chicory leaves.

Quality Improvement and Antioxidant Activity of Sugar-Snap Cookies Prepared Using Blends of Cereal Flour

In this study, we investigated the changes in quality and antioxidant activity of sugar-snap cookies prepared with different blends of refined wheat (WHF) and oat flour (OAF). The crude protein contents of OAF and WHF were 12.24% and 7.17%, respectively, and the fiber contents of were 3.45% and 0.31%, respectively; both were increased by adding OAF. However, the total starch contents were decreased by adding OAF. The β-glucan content of the samples increased considerably upon the addition of OAF. The water-holding capacity was increased after adding OAF compared to WHF (79.21%). Water binding in wet gluten contents decreased on the addition of OAF. Final viscosity increased on the addition of OAF. Antioxidant activity and total phenolic acid were increased upon the addition of OAF. The thickness of cookies prepared with OAF, WHF, 20% of WHF with OAF (WOB20), and WOB40 were 11.28, 12.35, 9.74, and 9.81 mm, respectively. The hardness of cookies prepared with WHF and WOF20 did not differ significantly, and analysis of the appearance of cookies showed that the cookies were increasingly cracked as the OAF content increased. Therefore, substituting WHF with OAF improved the quality and nutrient value of the cookies.

Composition of volatile aromatic compounds and minerals of tarhana enriched with cherry laurel (Laurocerasus officinalis)

Different concentrations of cherry laurel pulp (0, 5, 10, 15 and 20%) were used to produce tarhana samples. Volatile aromatic compounds and minor mineral content were investigated. Volatile aromatic compounds were analyzed by using GC-MS with SPME fiber and minor mineral values were evaluated with inductively coupled plasma optical emission spectrometer. The statistical analysis showed that addition of pulp affected volatile aromatic compounds and minor mineral content significantly. Thirty five volatile aromatic compounds were found in tarhana samples. The octanoic acid from acids, benzaldehyde (CAS) phenylmethanal from aldehydes, 6-methyl-5-hepten-2-one from ketones, octadecane (CAS) n-octadecane form terpenes, ethyl caprylate from esters and benzenemethanol (CAS) benzyl alcohol from alcohols had the highest percentage of volatile aromatic compounds. Tarhana samples were rich source of Mn, Cu and Fe content.