Blanching of red beet (Beta vulgaris L. var. conditiva) root. Effect of hot water or microwave radiation on cell wall characteristics

Progress on Conventional and Advanced Techniques of In Situ Transesterification of Microalgae Lipids for Biodiesel Production

Global warming and the depletion of fossil fuels have spurred many efforts in the quest for finding renewable, alternative sources of fuels, such as biodiesel. Due to its auxiliary functions in areas such as carbon dioxide sequestration and wastewater treatment, the potential of microalgae as a feedstock for biodiesel production has attracted a lot of attention from researchers all over the world. Major improvements have been made from the upstream to the downstream aspects related to microalgae processing. One of the main concerns is the high cost associated with the production of biodiesel from microalgae, which includes drying of the biomass and the subsequent lipid extraction. These two processes can be circumvented by applying direct or in situ transesterification of the wet microalgae biomass, hence substantially reducing the cost. In situ transesterification is considered as a significant improvement to commercially produce biodiesel from microalgae. This review covers the methods used to extract lipids from microalgae and various in situ transesterification methods, focusing on recent developments related to the process. Nevertheless, more studies need to be conducted to further enhance the discussed in situ transesterification methods before implementing them on a commercial scale.

Radio frequency energy inactivates peroxidase in stem lettuce at different heating rates and associate changes in physiochemical properties and cell morphology

Radio frequency (RF) is an emerging technology applied in blanching treatment as alternative to conventional treatment. This study aimed to investigate the effects of RF heating rate on peroxidase (POD) inactivating efficiency, physiochemical properties (texture, color and vitamin C) and cell structure of stem lettuce. POD enzyme inactivation efficiency increased with increased RF heating rate. When POD activity was reduced to <5%, better physiochemical properties and less cell damage occurred in RF heating compared with conventional hot water (HW) blanching (HWB); Relative electrolyte leakage (REL) analysis and microscopic observation suggested that the loss of integrity of cell walls and membranes, the decrease in turgor pressure and the weakened connections between adjacent cells leaded to the deterioration of physiochemical properties. The degrees of cell destruction varied with RF heating rates, which provide a new idea for RF blanching for producing different types of fruits and vegetables products (Solid and juice products).

Three Types of Red Beetroot and Sour Cherry Based Marmalades with Enhanced Functional Properties

The importance of bioactive compounds such as betalains and anthocyanins was highlighted in the present study by the valorization of red beetroot and sour cherry as an attempt to develop healthy products. The aim of the study was to obtain and characterize three types of marmalade based on red beetroot, sour cherry and both in 1:1 combination, obtained by heating at 95 °C for 30 min. Changes in total phenolic content, total flavonoids, betalains, anthocyanins and antioxidant activity were evaluated before and after the thermal treatment. Several other analyses such as color, rheological and textural analyses and confocal laser microscopy were performed to provide further information about the quality of the added-value food products. A significant decrease of 34% in betalains content was registered in the red beetroot marmalade due to the chemical changes in bioactives induced by the temperature. A satisfactory ABTS radical scavenging activity of 8.12 ± 0.38 mMol Trolox/g dry weight (dw) was obtained for the red beetroot and sour cherry based marmalade. The gelled structure was validated by the rheological and textural characteristics. The results highlighted the potential use of red beetroot and sour cherry as food raw materials, due to their particular profile of bioactive compounds.

Instant Controlled Pressure Drop as Blanching and Texturing Pre-Treatment to Preserve the Antioxidant Compounds of Red Dried Beetroot (Beta vulgaris L.)

Red beetroot is rich in bioactive compounds such as polyphenols, flavonoids, betaxanthins, betacyanins, among others. According to selected processing methods, the bioaccessibility of these compounds could be either enhanced or decreased. This study evaluated the effect of four different drying conditions: (1) Traditional Drying (TD), (2) Swell Drying (SD), (3) DIC Blanching + Traditional Drying (BTD), and (4) DIC Blanching + Swell Drying (BSD) on the antioxidant content and the antioxidant activity of red beetroots. Obtained results showed that in all the cases, by comparing to Traditional Drying (TD), the coupling of a DIC Blanching pre-treatment to a Swell Drying treatment (BSD) maintained or enhanced the preservation of the Total Phenolic Compounds (TPC), the Total Flavonoids Compounds (TFC), the Betanin Concentration (BC), the Trolox Equivalent Antioxidant Capacity (TEAC), and the Free Radical Scavenging Activity by DPPH (IC50) of red beetroots. Various studies have shown that thanks to the expanded and porous structure triggered by the Swell Drying process, it has been possible to achieve better antioxidants extraction and better whole quality. Hence, by coupling DIC as a blanching–steaming pre-treatment, it was possible to preserve better the antioxidant content and the antioxidant activity of red dried beetroots.

Optimization of the formula and processing of a sweet potato leaf powder-based beverage

For the development of a sweet potato leaf powder (SPLP)-based beverage, we investigated the effects of blanching methods on SPLP quality (including color, nutritional and functional compositions and antioxidant activity), and the effects of particle size and stabilizers on suspension stability of final product. The total polyphenol and antioxidant activity of SPLP of uncut group were 1.69 and 1.91 times those of cut group, respectively, and the indices of nutritional quality of copper, manganese and vitamin E of uncut group were significantly greater than cut group. The ultrafine SPLP-produced lowest gravitational sedimentation ratio (49%), indicating it had greatest suspension stability. The optimized formula of SPLP-based beverage was as follows: ultrafine SPLP of uncut group was mixed with 2.5% (w/w, powder basis) xanthan gum, 1% calcium lactate, 2% ascorbic acid, 12% maltodextrin, 20% xylitol, and 0.9% apple essence. The final product had high nutritional value along with consumer-acceptable flavor and texture.

Modification of Cell Wall Polysaccharides during Drying Process Affects Texture Properties of Apple Chips

The influences of hot air drying (AD), medium- and short-wave infrared drying (IR), instant controlled pressure drop drying (DIC), and vacuum freeze drying (FD) on cell wall polysaccharide modification were studied, and the relationship between the modifications and texture properties was analyzed. The results showed that the DIC treated apple chips exhibited the highest crispness (92) and excellent honeycomb-like structure among all the dried samples, whereas the FD dried apple chips had low crispness (10), the minimum hardness (17.4 N), and the highest volume ratio (0.76) and rehydration ratio (7.55). Remarkable decreases in the contents of total galacturonic acid and the amounts of water extractable pectin (WEP) were found in all the dried apple chips as compared with the fresh materials. The highest retention of WEP fraction (102.7 mg/g AIR) was observed in the FD dried apple chips, which may lead to a low structural rigidity and may be partially responsible for the lower hardness of the FD apple chips. In addition, the crispness of the apple chips obtained by DIC treatment, as well as AD and IR at 90°C, was higher than that of the samples obtained from the other drying processes, which might be due to the severe degradation of pectic polysaccharides, considering the results of the amounts of pectic fractions, the molar mass distribution, and concentrations of the WEP fractions. Overall, the data suggested that the modifications of pectic polysaccharides of apple chips, including the amount of the pectic fractions and their structural characteristics and the extent of degradation, significantly affect the texture of apple chips.

Dynamic microstructures and fractal characterization of cell wall disruption for microwave irradiation-assisted lipid extraction from wet microalgae

To extract lipids from wet microalgae through cell disruption, the effects of microwave treatment on the dynamic cell wall microstructures were investigated. The fractal dimension of raw, untreated microalgal cells was 1.46. The disruption level of microalgal cell walls was enhanced when microwave treatment temperature increased from 80 to 120°C, resulting in an increase in microalgal cell fractal dimension from 1.61 to 1.91. The cell wall thickness and pore diameters in cell walls increased from 0.11 to 0.59 μm and from 0.005 to 0.18 μm, respectively, when microwave treatment time increased from 0 to 20 min. The outer pectin layers of cell walls gradually detached and the porosity of inner cellulose layers increased when microwave treatment time increased to 26 min. The initial point of disruption appeared at the maximum curvature (approximately 1.01×10(7) m(-1)) of cell walls. Numbers of short-chain and saturated lipids increased because of microwave electromagnetic effect.