Evaluation of drying technologies for retention of physical quality and antioxidants in asparagus (Asparagus officinalis, L.)

Apple Cubes Drying and Rehydration. Multiobjective Optimization of the Processes

The effect of convective drying temperature (Td), air velocity (v), rehydration temperature (Tr), and kind of rehydrating medium (pH) was studied on the following apple quality parameters: water absorption capacity (WAC), volume ratio (VR) color difference (CD). To model, simulate, and optimize parameters of the drying and rehydration processes hybrid methods artificial neural network and multiobjective genetic algorithm (MOGA) were developed. MOGA was adapted to the apple tissue, where the simultaneous minimization of CD and VR and the maximization of WAC were considered. The following parameters range were applied, 50 ≤ Td ≤ 70 °C and 0.01 ≤ v ≤ 6 m/s for drying and 20 ≤ Tr ≤ 95 °C for rehydration. Distilled water (pH = 5.45), 0.5% solution of citric acid (pH = 2.12), and apple juice (pH = 3.20) were used as rehydrating media. For determining the rehydrated apple quality parameters the mathematical formulas were developed. The following best result was found. Td = 50.1 °C, v = 4.0 m/s, Tr = 20.1 °C, and pH = 2.1. The values of WAC, VR, and CD were determined as 4.93, 0.44, and 0.46, respectively. Experimental verification was done, the maximum error of modeling was lower than 5.6%.

Use of sucrose to diminish pore formation in freeze-dried heart valves

Freeze-dried storage of decellularized heart valves provides easy storage and transport for clinical use. Freeze-drying without protectants, however, results in a disrupted histoarchitecture after rehydration. In this study, heart valves were incubated in solutions of various sucrose concentrations and subsequently freeze-dried. Porosity of rehydrated valves was determined from histological images. In the absence of sucrose, freeze-dried valves were shown to have pores after rehydration in the cusp, artery and muscle sections. Use of sucrose reduced pore formation in a dose-dependent manner, and pretreatment of the valves in a 40% (w/v) sucrose solution prior to freeze-drying was found to be sufficient to completely diminish pore formation. The presence of pores in freeze-dried valves was found to coincide with altered biomechanical characteristics, whereas biomechanical parameters of valves freeze-dried with enough sucrose were not significantly different from those of valves not exposed to freeze-drying. Multiphoton imaging, Fourier transform infrared spectroscopy, and differential scanning calorimetry studies revealed that matrix proteins (i.e. collagen and elastin) were not affected by freeze-drying.

Phytochemical and physical properties of blueberries, tart cherries, strawberries, and cranberries as affected by different drying methods

The effects of hot-air drying (AD), freeze drying (FD) and Refractance Window drying (RWD) on the retention of anthocyanins, phenolics, flavonoids, vitamin C and B, and antioxidant capacity (ORAC) in blueberries, tart cherries, strawberries, and cranberries, as well as organic acids and proanthocyanins in cranberries and chlorogenic acid and catchins in blueberries were evaluated. Changes in color, glass transition, specific heat, and surface morphology of the dried fruits were also evaluated. The quality retention in the dried fruits was found to be product and drying method specific. The FD products exhibited a better retention of vitamin C, ORAC, anthocyanins, and phenolics than the AD and RWD fruits. The RWD produced samples with a less effective ORAC, anthocyanins, and phenolics retention, but a higher total vitamin B retention compared to the FD products. The AD-dried fruits displayed significantly lesser quality retention in most of the quality indexes measured in the study.

Drying Kinetics and Activation Energy of Asparagus Root (Asparagus racemosus Wild.) for Different Methods of Drying

Drying reduces the water activity of food product and hence increases the shelf life of the food. In the present study, fresh asparagus roots were pretreated in hot water at 80oC for 5 min. The methods of drying used for the study were tray drying, solar drying, vacuum drying and fluidized bed drying at four temperature levels 40, 50, 60 and 70oC. The complete drying of asparagus follow falling rate period only. The total time for drying decreases with increase in temperature of drying air from 40oC – 70oC. Fluidized bed dryer has a highest average drying rate as compare to tray dryer, solar dryer and vacuum dryer. Four empirical models, namely Page’s, Exponential, Generalized exponential and Logarithmic model were fitted in the drying data to describe the phenomena of drying process using a linearized regression technique. It was found that the Page’s model was best as it describe most precisely about the drying behavior of asparagus roots. The effective moisture diffusivity of asparagus roots varies from 7.14 × 10-9 to 3.70 × 10-8 m2/s and it was also found that diffusivity increases with increase in temperature. The activation energy was found to be from 11.797 to 30.318 kJ/mol.

Sensory evaluation of biscuits enriched with artichoke fiber-rich powders(Cynara scolymusL.)

The artichoke by‐products from the canning industry are mainly used for silage, being minimally revaluated. The ways of extraction of by‐products of artichoke into fiber‐rich powders modify their industrial applications in biscuits, as the sensory evaluation may change compared with the reference fiber (Pea fiber, P) used with commercial biscuit. In this sensory study biscuits enriched with fiber‐rich powders of artichoke (W, Ca) are compared with biscuits with the same percentage of the reference fiber (P) and control biscuits without fiber (B). For most of the sensory attributes of the biscuits enriched with artichoke fiber‐rich powders were perceived similar to the biscuits with the commercial reference fiber (P). The good sensory behavior of the biscuits with artichoke fiber‐rich powders during two storage conditions applied may confirm that the artichoke by‐products would be a suitable substitute for pea fiber in oven‐baked products, like wholemeal biscuits with high‐fiber content.

Studies on phytochemical, antioxidant, anti-inflammatory, hypoglycaemic and antiproliferative activities of Echinacea purpurea and Echinacea angustifolia extracts

CONTEXT

Echinacea (Asteraceae) is used because of its pharmacological properties. However, there are few studies that integrate phytochemical analyses with pharmacological effects.

OBJECTIVE

Evaluate the chemical profile and biological activity of hydroalcoholic Echinacea extracts.

MATERIALS AND METHODS

Density, dry matter, phenols (Folin-Ciocalteu method), flavonoids (AlCl₃ method), alkylamides (GC-MS analysis), antioxidant capacity (DPPH and ABTS methods), antiproliferative effect (SRB assay), anti-inflammatory effect (paw oedema assay, 11 days/Wistar rats; 0.4 mL/kg) and hypoglycaemic effect (33 days/Wistar rats; 0.4 mL/kg) were determined in three Echinacea extracts which were labelled as A, B and C (A, roots of Echinacea purpurea L. Moench; B, roots, leaves, flowers and seeds of Echinacea purpurea; C, aerial parts and roots of Echinacea purpurea and roots of Echinacea angustifolia DC).

RESULTS

Extract C showed higher density (0.97 g/mL), dry matter (0.23 g/mL), phenols (137.5 ± 2.3 mEAG/mL), flavonoids (0.62 ± 0.02 mEQ/mL), and caffeic acid (0.048 mg/L) compared to A and B. A, B presented 11 alkylamides, whereas C presented those 11 and three more. B decreased the oedema (40%) on day 2 similar to indomethacin. A and C showed hypoglycaemic activity similar to glibenclamide. Antiproliferative effect was only detected for C (IC₅₀ 270 μg/mL; 8171 μg/mL; 9338 μg/mL in HeLa, MCF-7, HCT-15, respectively).

DISCUSSION AND CONCLUSION

The difference in the chemical and pharmacological properties among extracts highlights the need to consider strategies and policies for standardization of commercial herbal extracts in order to guarantee the safety and identity of this type of products.

Improved curdlan production with discarded bottom parts of Asparagus spear

BACKGROUND

This work evaluated the improvement of curdlan production of Agrobacterium sp. ATCC 31749 by using culture medium containing juice of discarded bottom part of green Asparagus spear (MJDA). Curdlan production was carried out using Agrobacterium sp. ATCC 31749 in flasks with different volumes of MJDA and its non-juice-adding control (CK) incubated in shaker at 30 °C, 200 rpm rotation for 168 h.

RESULTS

All MJDA media increased Agrobacterium sp. ATCC 31749 cell mass and enhanced the cells' ability to utilise sucrose, the carbon source for curdlan biosynthesis, and thereby produced higher concentration of curdlan than CK which is used for commercial production of curdlan. After 168 h of fermentation, 10% MJDA produced 40.2 g/l of curdlan whiles CK produced 21.1 g/l. Curdlan production was increased by 90.4% higher in 10% MJDA than CK. Curdlan produced by 10% MJDA contains 1.2 and 1.5 µg/ml of Asparagus flavonoids and saponins respectively as additives which have wide range of health benefits. The mass of sucrose needed to produce 1.0 g curdlan by Agrobacterium sp. ATCC 31749 in CK is 1.7-fold more than in 10% MJDA.

CONCLUSION

The results strongly revealed that 5-10% MJDA is a good curdlan fermentation media which increase curdlan production yield with cheaper cost of production and simultaneously reduce environmental waste resulting from the large scaled discarded bottom parts of green Asparagus spear during Asparagus production.

Microwave Drying Characteristics of Soybeans in Single and Variable Microwave Power Density

Drying characteristics of soybeans under different microwave (MW) processing schemes were studied in regard to energy aspects. For drying in a single microwave power density, the experiments were carried out at a constant MW output power throughout the process. It was found that the drying rate is enhanced together with reduced energy consumption at higher single power density, but the soybean cracking ratio is increased gradually from 2 % to 40 % when the power density was changed from 0.2 W/g to 0.8 W/g. Efforts were made to reach a compromise between the drying rate and dried soybean quality by varying the MW power density in several steps overall the drying process, but soybean cracking occurred at a higher ratio due to the fluctuation of drying rate. Microwave drying of soybeans under the power density less than 0.2 W/g with slow and stable drying rate can achieve the soybean cracking ratio controlled within 5 % and lower energy consumption.

The Influence of Refractance Window Drying on Qualitative Properties of Kiwifruit Slices

In this research, effect of Refractance Window (RW) drying on the quality properties of the kiwifruit samples was investigated. Drying temperatures of 80–100 °C, slice thickness of 0.8–2.4 mm and Mylar thickness of 100–300 µm were the independent variables and different qualitative attributes including drying duration, textural hardness, colour, rehydration ratio and organoleptic properties were responses monitored in each situation. Drying temperature was the most important factor contributed to quality features of RW dried kiwifruits with significant effects on all properties. Similarly, slice thickness influenced nearly all quality traits except textural hardness and some colour indices. However, Mylar membrane thickness failed to affect about every qualitative property of kiwifruit samples significantly. The majority of organoleptic properties of RW dried kiwifruits, including flavour, colour, texture, shrinkage and overall acceptance, were judged to be in the range of medium to good quality (scores of 3–4) by panellists.

Evaluation of Drying and Storage Conditions on Nutritional and Sensory Properties of Dried Galega Kale (Brassica oleracea L. var. Acephala)

This work evaluated the effect of the air-drying temperature and vacuum packaging on quality and nutritional compounds of dehydrated galega kale, previously steam blanched, during 5 months of storage. When compared with the vacuum packaged kale, the packaging without vacuum yielded improved nutritional features, in general. This approach combined with a drying temperature of 40°C resulted in retention percentages of 62, 38, 92, and 48% for vitamin C, total phenolic content, total antioxidant capacity, and chlorophylls, respectively. The acceptance of the dried product by the consumer was assessed through a focus group. The participants classified the product as a practical and convenient alternative to cook healthier dishes. The appearance of dried galega kale was described as being fragile and being with nice smell, natural colour, and flavour similar to the fresh product. In conclusion, the herein presented product was addressed as an innovation with multiple possible applications in several recipes.

Improving the Nutritional Quality of Microwave-vacuum Dried Strawberries: A Preliminary Study

Microwave-vacuum drying is an up-to-date technique for the conservation of fruits and vegetables, resulting in products with improved texture and colour. In order to evaluate the effects on the content of ascorbic acid, anthocyanins and phenolic compounds, and antioxidant capacity, three strawberry varieties were subjected to microwave-vacuum (MV) drying combined with convective pre- and post-drying, convective drying, and freeze-drying. The MV drying procedure comprised immersion in a pretreatment bath, pre-drying in a belt dryer to a moisture load of approx 45 g/100 g dry matter, and microwave treatment at 4 kPa for 8 min, leading to products with 5 g/100 g moisture. During post-drying, the moisture content was further reduced to approx 2 g/100 g. Convective drying and MV drying decreased the content of ascorbic acid to approx 40% of the initial value, phenolic compounds to approx 35%, and the antioxidative capacity to approx 60%. No reduction was observed in freeze-dried strawberries. Bypassing the pre-treatment bath, extending residence time in the pre-dryer to reduce temperature peaks, and reducing MV treatment time increased the recovery of ascorbic acid to approx 65%. Phenolic compounds remained stable, and the reduction of the antioxidative capacity was limited to 10% – 25%. Except ascorbic acid, the residual concentration of nutritionally relevant compounds after improving the processing conditions was close to the values as observed for freeze-dried products.

Effect of processing on phenolic antioxidants of fruits, vegetables, and grains--a review

Understanding the influence of processing operations such as drying/dehydration, canning, extrusion, high hydrostatic pressure, pulsed electric field, and ohmic heating on the phytochemicals of fruits, vegetables, and grains is important in retaining the health benefiting properties of these antioxidative compounds in processed food products. Most of the previous investigations in the literature on the antioxidants of fruits, vegetables, and grains have shown that food-processing operations reduced the antioxidants of the processed foods, which is also the usual consumer perception. However, in the last decade some articles in the literature reported that the evaluation of nutritional quality of processed fruits and vegetables not only depend on the quantity of vitamin C but should include analyses of other antioxidant phytochemicals and antioxidant activity. Thermal processing increased the total antioxidant activity of tomato and sweet corn. Most importantly, analysis also depends on the condition, type, and mechanism of antioxidant assays used. This review aims to provide concise information on the influence of various thermal and nonthermal food-processing operations on the stability and kinetics of health beneficial phenolic antioxidants of fruits, vegetables, and grains.

Changes in microbial diversity of brined green asparagus upon treatment with high hydrostatic pressure

The application of high hydrostatic pressure (HHP, 600MPa, 8 min) on brined green asparagus and the changes in bacterial diversity after treatments and during storage at 4 °C (30 days) or 22 °C (10 days) were studied. HHP treatments reduced viable cell counts by 3.6 log cycles. The residual surviving population did not increase during storage at 4 °C. However, bacterial counts significantly increased at 22 °C by day 3, leading to rapid spoilage. The microbiota of green asparagus was composed mainly by Proteobacteria (mainly Pantoea and Pseudomonas), followed by Firmicutes (mainly Lactococcus and Enterococcus) and to a less extent Bacteroidetes and Actinobacteria. During chill storage of untreated asparagus, the relative abundance of Proteobacteria as well as Enterococcus and Lactococcus decreased while Lactobacillus increased. During storage of untreated asparagus at 22 °C, the abundance of Bacteroidetes decreased while Proteobacteria increased during late storage. The HHP treatment determined a reduction of the Proteobacteria both early after treatment and during chill storage. In the HHP treated samples stored at 22 °C, the relative abundance of Pseudomonas rapidly decreased at day 1, with an increase of Bacteroidetes. This was followed by a marked increase in Enterobacteriaceae (Escherichia) simultaneously with increase in viable counts and spoilage. Results from the study indicate that the effect of HHP treatments on the viability ofmicrobial populations in foods also has an impact on the dynamics of microbial populations during the storage of the treated foods.

Effect of different cooking methods on total phenolic contents and antioxidant activities of four Boletus mushrooms

The influences of cooking methods (steaming, pressure-cooking, microwaving, frying and boiling) on total phenolic contents and antioxidant activities of fruit body of Boletus mushrooms (B. aereus, B. badius, B. pinophilus and B. edulis) have been evaluated. The results showed that microwaving was better in retention of total phenolics than other cooking methods, while boiling significantly decreased the contents of total phenolics in samples under study. Effects of different cooking methods on phenolic acids profiles of Boletus mushrooms showed varieties with both the species of mushroom and the cooking method. Effects of cooking treatments on antioxidant activities of Boletus mushrooms were evaluated by in vitro assays of hydroxyl radical (OH·) -scavenging activity, reducing power and 1, 1-diphenyl-2-picrylhydrazyl radicals (DPPH·) -scavenging activity. Results indicated the changes of antioxidant activities of four Boletus mushrooms were different in five cooking methods. This study could provide some information to encourage food industry to recommend particular cooking methods.

Kinetic Models of Evaporation and Total Phenolics Degradation during Pomegranate Juice Concentration

Pomegranate juice was concentrated by conventional heating at different temperatures (45, 50, 55, 60, and 65°C), and the effect of temperature on evaporation rate and on thermal degradation of total phenolics was investigated. Concentration kinetics modeling was developed based on thin-layer drying models. The logarithmic model was found to give better predictions than the others. The temperature dependence of the model constants was expressed by polynomial relationships. In addition, a first-order decay model, with an Arrhenius and a polynomial dependency on temperature and water content, respectively, was used to describe the joint influence of temperature and moisture content on the thermal degradation of total phenolics in a concentration process of pomegranate juice.

Bioactive compounds, antioxidant and binding activities and spear yield of Asparagus officinalis L

The aim of this investigation was to find a proper harvesting period and establishing fern number, which effects the spear yield, bioactive compounds and antioxidant activities of Asparagus officinalis L. Spears were harvested at 2, 4, and 6 weeks after sprouting. Control for comparison was used without harvest. Spears and total yield increased with prolonged spear harvest period. In harvest of 6 weeks long optimum spear yield was the highest and fern numbers were 5 ~ 8. Bioactive compounds (polyphenols, flavonoids, flavanols, tannins and ascorbic acid) and the levels of antioxidant activities by ferric-reducing/antioxidant power (FRAP) and cupric reducing antioxidant capacity (CUPRAC) assays in asparagus ethanol extracts significantly differed in the investigated samples and were the highest at 6 weeks harvest period (P < 0.05). The first and the second segments from the tip significantly increased with the increase of catalase (CAT). It was interesting to investigate in vitro how human serum albumin (HSA) interacts with polyphenols extracted from investigated vegetables. Therefore the functional properties of asparagus were studied by the interaction of polyphenol ethanol extracts with HSA, using 3D- FL. In conclusion, antioxidant status (bioactive compounds, binding and antioxidant activities) improved with the harvesting period and the first segment from spear tip. Appropriate harvesting is effective for higher asparagus yield and its bioactivity.

Microwave, Air and Combined Microwave-Air Drying of Grape Leaves (Vitis vinifera L.) and the Determination of Some Quality Parameters

Grape leaves (Vitis vinifera L.) weighing 50 g (±0.08) with a moisture of 4.08 kg(moisture) kg−1(dry matter) (75.35% wb) were dried using three different drying methods: microwave, air and combined microwave-air. Drying continued until the leaf moisture decreased to 0.14 (±0.01) kg(moisture) kg−1(dry matter) (9.07% (±0.20) wb). Drying periods lasted 5–11, 30–70 and 1.5–6 min for microwave, air and combined microwave-air drying, respectively, depending on the drying level. In this study, measured values of moisture were compared with values of predicted obtained from several thin-layer equations; the Alibas Model was found to have the best fit. The optimum drying period, color and ascorbic acid content were obtained by using the combined microwave-air drying method with the optimum combination of 500 W of microwave power at a temperature of 75°C.

Thin layer drying of tomato slices

The hot air convective drying characteristics of blanched tomato (Lycopersicon esculantum L.) slices have been investigated. Drying experiments were carried out at four different temperatures (50, 60, 65 and 70 °C). The effect of drying temperatures on the drying behavior of the tomato slices was evaluated. All drying experiments had only falling rate period. The average effective diffusivity values varied from 0.5453 × 10(-9) to 2.3871 × 10(-9) m(2)/s over the temperature range studied and the activation energy was estimated to be 61.004 kJ/mol. In order to select a suitable form of the drying curve, six different thin layer drying models (Henderson-Pabis, Page, Diamante et al., Wang and Singh, Logarithmic and Newton models) were fitted to the experimental data. The goodness of fit tests indicated that the Logarithmic model gave the best fit to experimental results, which was closely followed by the Henderson-Pabis model. The influence of varied drying temperatures on quality attributes of the tomato slices viz. Hunter color parameters, ascorbic acid, lycopene, titratable acidity, total sugars, reducing sugars and sugar/acid ratio of dried slices was also studied. Slices dried at 50 and 60 °C had high amount of total sugars, lycopene, sugar/acid ratio, Hunter L- and a-values. Drying of slices at 50 °C revealed optimum retention of ascorbic acid, sugar/acid ratio and red hue, whereas, drying at higher temperature (65 and 70 °C) resulted in a considerable decrease in nutrients and colour quality of the slices.