A comparative study on the effect of microwave and conventional oven heating on the quality of flaxseeds

Moisture content in dehulled sesame seeds: A key factor affecting the aroma and safety quality of sesame paste (tahini)

This study aimed to investigate the influence of the moisture content of dehulled sesame seeds on the aroma formation and harmful substances in sesame paste (SP). The SP samples were made of dehulled sesame seeds with moisture contents of 5%, 10%, 15%, 20%, and 25% and denoted as T5, T10, T15, T20, and T25, respectively. The results revealed that adjusting the moisture content had a significant impact on aroma compounds, color intensity, and sensory properties. SP pre-adjusted to a moisture content of 10% exhibited the smallest L* value and the highest browning strength. Using gas chromatography-olfactometry-mass spectrometry analysis, the researchers identified 38 aroma-active compounds in the SP, with pyrazines being the most abundant, contributing to roasted sesame and nutty aromas. Additionally, the presence of pyrrole and furan derivatives led to enhanced caramel and almond aromas, positively influencing the overall sensory properties. T10 demonstrated the highest levels of roasted sesame and nutty odors. Furthermore, the regulation of moisture content also affected the formation of harmful compounds, such as heterocyclic amines and polycyclic aromatic hydrocarbons (PAHs). Notably, the sample made of the sesame seeds with 10% and 15% moisture content exhibited the lowest total PAHs content (18.21-28.91 ng/g) and PAH4 content (non-detectable-0.15 ng/g). The carcinogen benzo[a]pyrene was not detected in any of the samples, ensuring a safer product. The pre-adjustment of moisture content in SP appears to be a promising approach to improve both its flavor and safety qualities.

Comparison of microwave and hot-air roasting on microstructure of sesame seed, aroma-active, hazardous components, and sensory perception of sesame oil

The unclear effects of microwaves, as a greener alternative to hot air, on sensory perception, aroma, and hazardous components of sesame oil were investigated. Microwaves (900 W, 6-10 min) created more seed porosity and cell destruction and facilitated more γ-tocopherol release in sesame oil (349.30-408.50 mg/kg) than 200 °C, 20 min hot air (304.90 mg/kg). Microwaves (6-10 min) generated more aromatic heterocyclics (42.40-125.12 mg/kg) and aldehydes (5.15-2.08 mg/kg) in sesame oil than hot air (25.59 mg/kg and 1.34 mg/kg). Microwaves (6 min) produced sesame oil with a stronger roasted sesame flavour, and weaker bitter and burnt flavour than hot air. Microwaves reduced harman (≤775.19 ng/g), norharman (≤1,069.99 ng/g), and benzo(a)pyrene (≤1.59 μg/kg) in sesame oil than hot air (1,319.85 ng/g, 1,168.40 ng/g, and 1.83 μg/kg). Appropriate microwave is a promising alternative to hot air in producing sesame oil with a better sensory profile, more bioactive, and less carcinogenic components.

A study of flavor variations during the flaxseed roasting procedure by developed real-time SPME GC-MS coupled with chemometrics

Volatile compound variations during the roasting procedure play an essential role in the flaxseed-related product. In this work, we proposed a new strategy to high-throughput characterize the dynamic variations of flavors in flaxseed. Volatile compounds released at various roasting times were comprehensively investigated by a newly developed real-time solid-phase microextraction coupled with gas chromatography-mass spectrometry (GC-MS). Raw data files were analyzed by our advanced GC-MS data analysis software AntDAS-GCMS. Chemometric methods such as principal component analysis and partial least squares-discrimination analysis have realized the differences of samples with various roasting times. Finally, a total of 51 compounds from 11 aromas were accurately identified and confirmed with standards, and their variations as a function of roasting time were studied. In conclusion, we provided a new solution for the online monitoring of volatile compounds during the industrial roasting process.

The physicochemical stability and in vivo gastrointestinal digestion of flaxseed milk: Implication of microwave on flaxseed

The current study was to investigate how microwave on flaxseed affected the physicochemical stability and gastrointestinal digestion of oil bodies (OBs) in flaxseed milk. Flaxseed was subjected to moisture adjustment (30-35 wt%, 24 h), and microwave exposure (0-5 min, 700  W). Microwave treatment slightly weakened the physical stability of flaxseed milk indicated by Turbiscan Stability Index, but there were no visual phase separation during 21 days of storage at 4 °C. Upon microwave treatment, OBs experienced the layer-by-layer encapsulation into loose interface embedding by storage protein-gum polysaccharide complex from bulk phase, resulting in lower viscoelasticity of flaxseed milk. The OBs underwent earlier interface collapse and lipolysis during gastrointestinal digestion, followed by synergistic micellar absorption, faster chylomicrons transport within enterocytes of rats fed flaxseed milk. The accumulation of α-linolenic acid and synergistic conversion into docosapentaenoic and docosahexanoic acids in jejunum tissue were achieved accompanied by the interface remodeling of OBs in flaxseed milk.

Effect of Flaxseed Addition on the Quality and Storage Stability of Sesame Paste

The flaxseed-sesame paste (FSP) was prepared by mixing the heat-treated flaxseed and sesame seeds in different proportions and grinding them in a colloid mill to obtain a FSP. In this study, flaxseed was added to sesame paste (SP) at different addition to assess its effect on the rheological properties, textural properties, and particle size. The effect of flaxseed addition on lipid oxidation and volatile aldehydes and ketones during storage of SP was investigated by accelerated oxidation experiments (63°C, 60 days). Notably, the addition of all different additions of flaxseed increased the linolenic acid content, and also enhanced the hardness, cohesiveness, and viscosity of SP. However, it increased the rate of lipid oxidation in SP during storage, mainly in the form of higher acid value (AV) and malondialdehyde (MDA) content. The content of volatile aldehydes and ketones from lipid oxidation increased significantly with storage time. It was found by using cluster analysis that mixing flaxseed with SP at a ratio of 20 g/100 g had little effect on its storage stability, the sample had a higher overall quality than the addition of 40 g/100 g flaxseed, and its linolenic acid content was 18.7 times higher than that of the SP. Collectively, the results indicated that the addition of flaxseed at an appropriate proportion might be a feasible way to prepare the functional formulated SP.

Composition, processing, and quality control of whole flaxseed products used to fortify foods

Whole flaxseed (flour) as a good source of omega-3 fatty acid and phytochemicals with excellent nutritional and functional attributes has been used to enrich foods for health promotion and disease prevention. However, several limitations and contemporary challenges still impact the development of whole flaxseed (flour)-enriched products on the global market, such as naturally occurring antinutritional factors and entrapment of nutrients within food matrix. Whole flaxseed (flour) with different existing forms could variably alter the techno-functional performance of food matrix, and ultimately affect the edible qualities of fortified food products. The potential interaction mechanism between the subject and object components in fortified products has not been elucidated yet. Hence, in this paper, the physical structure and component changes of flaxseed (flour) by pretreatments coupled with their potential influences on the edible qualities of multiple fortified food products were summarized and analyzed. In addition, several typical food products, including baked, noodle, and dairy products were preferentially selected to investigate the potential influencing mechanisms of flaxseed (flour) on different substrate components. In particular, the altered balance between water absorption of flaxseed protein/gum polysaccharides and the interruption of gluten network, lipid lubrication, lipid-amylose complexes, syneresis, and so forth, were thoroughly elucidated. The overall impact of incorporating whole flaxseed (flour) on the quality and nutritional attributes of fortified food products, coupled with the possible solutions against negative influences are aimed. This paper could provide useful information for expanding the application of whole flaxseed (flour) based on the optimal edible and nutritional properties of fortified food products.

Impact of different microwave treatments on food texture

Electromagnetic waves are frequently used for food processing with commercial or domestic type microwave ovens at present. Microwaves cause molecular movement by the migration of ionic particles or rotation of dipolar particles. Considering the potential applications of microwave technique in food industry, it is seen that microwaves have many advantages such as saving time, better final product quality (more taste, color, and nutritional value), and rapid heat generation. Although microwave treatment used for food processing with developing technologies have a positive effect in terms of time, energy, or nutrient value, it is also very important to what extent they affect the textural properties of the food that they apply to. For this purpose, in this study, it has been investigated that the effects of commonly used microwave treatments such as drying, heating, baking, cooking, thawing, toasting, blanching, frying, and sterilization on the textural properties of food. In addition, this study has also covered the challenges of microwave treatments and future work. In conclusion, microwave treatments cause energy saving due to a short processing time. Therefore, it can be said that it affects the textural properties positively. However, it is important that the microwave processing conditions used are chosen appropriately for each food material.

Influences of microwave exposure to flaxseed on the physicochemical stability of oil bodies: Implication of interface remodeling

This study aimed to investigate the influences of microwave (MV) exposure to flaxseed on the physicochemical stability of oil bodies (OBs) focused on the interface remodeling. The results showed that the intracellular OBs subjected to absolute rupture and then partial dispersion by protein bodies visualized by TEM following MV exposure (1-5 min; 700 W). After aqueous extraction, native flax OBs manifested excellent spherical particles with completely intact surface and wide particle size distribution (0.5-3.0 μm) examined by cryo-SEM. Upon 1-5 min of MV exposure, the defective interface integrity and beaded morphology were successively observed for flax OBs, accompanied by the impaired physical stability and rheological behavior due to the newly assembled phospholipid/protein interface. Notably, the profitable migration of phenolic compounds effectively suppressed the lipid peroxidation and protein carbonylation in flax OBs. Thus, MV exposure (1-5 min; 700 W) was unfavorable for improving the physical stability of flax OBs.

A review of the microwave-assisted synthesis of carbon nanomaterials, metal oxides/hydroxides and their composites for energy storage applications

Currently, nanomaterials are considered to be the backbone of modern civilization. Especially in the energy sector, nanomaterials (mainly, carbon- and metal oxide/hydroxide-based nanomaterials) have contributed significantly. Among the various green approaches for the synthesis of these nanomaterials, the microwave-assisted approach has attracted significant research interest worldwide. In this context, it is noteworthy to mention that because of their enhanced surface area, high conducting nature, and excellent electrical and electrochemical properties, carbon nanomaterials are being extensively utilized as efficient electrode materials for both supercapacitors and secondary batteries. In this review article, we briefly demonstrate the characteristics of microwave-synthesized nanomaterials for next-generation energy storage devices. Starting with the basics of microwave heating, herein, we illustrate the past and present status of microwave chemistry for energy-related applications, and finally present a brief outlook and concluding remarks. We hope that this review article will positively convey new insights for the microwave synthesis of nanomaterials for energy storage applications.