Peanut oils from roasting operations: An overview of production technologies, flavor compounds, formation mechanisms, and affecting factors

Fragrant peanut oils (FPOs) are commonly defined as edible peanut oils having strong natural roasted peanut flavor without peculiar unpleasant odors and produced from peanut kernels through roasting/steaming and pressing operations, etc. The flavor of FPOs plays a crucial role in their acceptability and applications and their flavor profiles are an important factor in determining their overall quality. This paper presents a systematic literature review of recent advances and knowledge on FPOs, especially their flavors, in which it is focused on the evaluation of volatile compounds, the factors influencing the formation of flavor compounds, and formation mechanisms of those typical flavor compounds. More than 300 volatiles are found in FPOs, while some key aroma-active compounds and their potential formation pathways are examined. Factors that have big influences on flavor are discussed also, including the properties of raw materials, processing technologies, and storage conditions. Ultimately, the paper highlights the challenges facing, including the challenges in flavor analysis, the relationship between volatile compounds and sensory attributes, as well as the opening of the blackboxes of flavor formations during the processing steps, etc.

Comparison evaluation pretreatments on the quality characteristics, oxidative stability, and volatile flavor of walnut oil

In this study, we applied various thermal pretreatment methods (e.g., hot-air, microwave, and stir-frying) to process walnut kernels, and conducted comparative analysis of the physicochemical properties, nutritional components, in vitro antioxidant activity, and flavor substances of the extracted walnut oil (WO). The results indicated that, thermal pretreatment significantly increased the extraction of total trace nutrients (e.g., total phenols, tocopherols, and phytosterols) in WO. The WO produced using microwave had 2316.71 mg/kg of total trace nutrients, closely followed by the stir-frying method, which yielded an 11.22% increase compared to the untreated method. The WO obtained by the microwave method had a higher Oxidative inductance period (4.05 h) and oil yield (2.48%). After analyzing the flavor in WO, we found that aldehydes accounted for 28.77% of the 73 of volatile compounds and 58.12% of the total flavor compound content in microwave-pretreated WO, these percentages were higher than those recorded by using other methods. Based on the comprehensive score obtained by the PCA, microwave-pretreatment might be a promising strategy to improve the quality of WO based on aromatic characteristics.

Sesame Seeds: A Nutrient-Rich Superfood

Sesame seeds (Sesamum indicum L.) have been cultivated for thousands of years and have long been celebrated for their culinary versatility. Beyond their delightful nutty flavor and crunchy texture, sesame seeds have also gained recognition for their remarkable health benefits. This article provides an in-depth exploration of the numerous ways in which sesame seeds contribute to overall well-being. Sesame seeds are a powerhouse of phytochemicals, including lignans derivatives, tocopherol isomers, phytosterols, and phytates, which have been associated with various health benefits, including the preservation of cardiovascular health and the prevention of cancer, neurodegenerative disorders, and brain dysfunction. These compounds have also been substantiated for their efficacy in cholesterol management. Their potential as a natural source of beneficial plant compounds is presented in detail. The article further explores the positive impact of sesame seeds on reducing the risk of chronic diseases thanks to their rich polyunsaturated fatty acids content. Nevertheless, it is crucial to remember the significance of maintaining a well-rounded diet to achieve the proper balance of n-3 and n-6 polyunsaturated fatty acids, a balance lacking in sesame seed oil. The significance of bioactive polypeptides derived from sesame seeds is also discussed, shedding light on their applications as nutritional supplements, nutraceuticals, and functional ingredients. Recognizing the pivotal role of processing methods on sesame seeds, this review discusses how these methods can influence bioactive compounds. While roasting the seeds enhances the antioxidant properties of the oil extract, certain processing techniques may reduce phenolic compounds.

Pre-regulation of the water content impacts on the flavor and harmful substances of sesame paste

In this study, the influence of pre-regulation of the water content (5-25 %) on the harmful substances and aroma compounds of sesame paste (SP) was investigated. The results indicated that pre-regulation of the water content reduced the generation of harmful substances in SP. Notably, the total heterocyclic amine content in SP-15 was significantly lower than in other samples. SP-10 had the lowest total polycyclic aromatic hydrocarbon content, while SP-5 exhibited the lowest PAH4 content. Using solvent-assisted aroma evaporation and GC-O-MS, 50 aroma compounds were identified in SP. Pre-regulation of water content in SP led to an elevated concentration of heterocyclic compounds thereby imparting a diverse aromatic profile. It enhanced the perceived intensity of roasted sesame and salty pastry aromas while reducing the perceived intensity of fermentation and burnt aromas. The findings suggested the pre-regulation of the water content played a crucial role in aroma modulation and harmful substances control in SP.

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.

Authenticity Assessment from Sesame Seeds to Oil and Sesame Products of Various Origin by Differential Scanning Calorimetry

The aim of this study was to conduct thermal characterization of sesame seeds and oils from various geographical origins (Ethiopia, India, Nigeria, Sudan, Turkey), different method of extraction (hexane and cold-pressing), and different types of derived products (halva and tahini). Thermal characterization was investigated using differential scanning calorimetry (DSC), which showed that origin of the seeds has no influence on the melting profile of sesame oil (peak temperature and enthalpy). Method of extraction (hexane and cold-pressing) influenced the peak temperatures of the resulting oils (p ≤ 0.05). The addition of 20% of palm olein to pure sesame oil influenced the significant changes in thermodynamic parameters such as peak temperature (Tm2), which was lowered from −5.89 °C to −4.99 °C, peak half width (T1/2), elevated from 3.01 °C to 4.52 °C, and the percentage of first peak area (% peak 1) lowered from 87.9 to 73.2% (p ≤ 0.05). The PCA method enabled to distinguish authentic and adulterated sesame oils of various origins. There were no significant differences in thermal properties among the products (halva, tahini) and the authentic sesame oil (p > 0.05). The obtained results showed DSC feasibility to characterize sesame oil and sesame products in terms of authenticity.

Characterizing the Bioactive Ingredients in Sesame Oil Affected by Multiple Roasting Methods

Roasting is an important step in sesame (Sesamum indicum L.) processing. The current research was undertaken to evaluate the oil content, fatty acid (FA) profiles, and physicochemical characteristics of oil recovered from sesame roasted by different methods (cooker oven, stovetop pan, microwave, and electric frying pan). Roasting sesame seeds changed their oil content according to the roasting method used, with content ranging from 49.83% in control to 59.85% in the roasting by microwave. In oils recovered from raw or roasted seeds, seven fatty acids were obtained through gas chromatography. Changes in the fatty acid profiles occurred in all the treatments, and the total unsaturated fatty acid content was higher than that of saturated fatty acids. The obtained peroxide number of sesame oils was inside the rate of 3.90 meq/kg oil for microwave treatment versus 1.59 meq/kg oil for unroasted. The highest acid value was with the stovetop pan treatment at 3.78 mg/g, followed by the microwave treatment at 3.24 mg/g; the oven treatment gave the lowest value at 1.66 mg/g. The lowest iodine value was observed with the electric frying pan treatment (102.30/100 g oil), and phytosterols were most abundant with the microwave treatment. Moreover, the phenolic and flavonoid contents and antioxidant activity were the highest with the microwave roasting. The FTIR spectrum illustrated slight differences in peaks intensity (1738, 1454, 1151, 710 cm⁻¹) between the roasting methods used. The finding of the current investigation of roasting methods was that the fatty acid profiles were across methods. As is clear from the obtained results, the microwave roasting treatment is the favoured roasting method for the healthiest sesame seed oil contents. Sesame seeds are considered a significant and abundant resource with numerous beneficial nutrients that positively affect human health.

Comparative assessment of the effect of pretreatment with microwave and roast heating on the quality of black sesame pastes

Heating is a key procedure in producing sesame paste. The effects of microwave heating and conventional roasting on the physicochemical features, protein profiles, and volatile compounds of black sesame pastes made of black sesame seeds from Burma and China were evaluated in this study. All heating treatments decreased the moisture contents of black sesame pastes, and roasting yielded lower moisture levels, although with similar chroma (p < 0.05). The samples subjected to microwave heating had remarkably lower peroxide values than those heated with roasting (p < 0.05). Chinese microwave-heated samples had a higher nitrogen solubility index than roasting (p < 0.05). Both microwave and roasting increased the contents of the volatiles notably. SDS-PAGE showed that the intensity of the 2-15 kDa band decreased markedly after heating and nearly diminished for roasting samples, suggesting that roasting was more remarkable for the promotion to the protein aggregation. The results indicated that the quality traits of black sesame paste not only depend on the heating methods, but also the heating power/temperature and duration, and the source of the materials.

Effects of different preheat treatments on volatile compounds of camellia (Camellia oleifera Abel.) seed oil and formation mechanism of key aroma compounds

In this study, volatile compounds of camellia seed oil (CSO) prepared by different preheat treatments (microwave, frying, roasting, and steaming) were identified by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME/GC-MS). A total of 107 volatile compounds were identified in CSO samples, including aldehydes (16), alcohols (6), ketones (3), heterocyclic compounds (26), esters (23), hydrocarbons (15), and others (17). Among them, untreated CSO is mainly hydrocarbons, roasting and steaming CSO are mainly aldehydes and alcohols, while microwave and roasting CSO are dominated by aldehydes and heterocyclic compounds. Fourteen volatile compounds with high relative odor activity value (ROAV ≥ 1) were selected as key aroma compounds (KACs). Principal Component Analysis (PCA) and Cluster Analysis (CA) were performed on 14 KACs, which determined that there were 3, 3, 3, 7, and 6 characteristic aroma compounds (CACs) in untreated, microwaved, frying, roasting, and steaming CSO. Additionally, the potential formation pathways and mechanism of KACs were discussed. PRACTICAL APPLICATIONS: Flavor is an important factor for consumers to choose edible oils, and it is also one of the indicators of oil quality. Different flavors of CSO can cater to the needs of different consumers. CSO manufactories can choose different preheat treatments to produce CSO with various flavors to meet different customers' need. CSO with new flavor can extend its market share and increase its value.

Effect of conventional oven roasting treatment on the physicochemical quality attributes of sesame seeds obtained from different locations

The impacts of conventional oven roasting at different temperatures and for different times on the physicochemical attributes of sesame seeds obtained from different regions was assessed. The color characteristics (a*, b*, and L* values), ash, moisture, protein, oil, total phenolic, and antioxidant activity of raw sesame seeds and the peroxide value, p-anisidine, fatty acids, and tocopherols of sesame oil varied with source. Oven roasting temperature and time significantly affected the physicochemical properties and bioactive components of sesame seeds and the oil quality from different countries. Roasting variably increased the a* value, antioxidant activity, protein, oil, total phenolic, and tocopherol content, and p-anisidine and peroxide values, whereas it reduced b* and L* values, moisture, and linolenic acid content of sesame seeds from different countries. Roasting conditions and growing locations affected the physiochemical composition and bioactive compounds of seeds. Such factors can influence the quality attributes of sesame seeds and oil and should be considered during processing.

Root diversity in sesame (Sesamum indicum L.): insights into the morphological, anatomical and gene expression profiles

Sesame harbors a large diversity in root morphological and anatomical traits and a high root biomass improves the plant aboveground biomass as well as the seed yield. Sesame provides one of the most nutritious and healthy vegetable oils, sparking an increasing demand of its seeds. However, with the low yield and productivity of sesame, there is still a huge gap between the seed demand and supply. Improving the root system has a high potential to increase crop productivity, but information on the diversity of the sesame root systems is still lacking. In this study, 40 diverse sesame varieties were grown in soil and hydroponics systems and the diversity of the root system was investigated. The results showed that sesame holds a large root morphological and anatomical diversity, which can be harnessed in breeding programmes. Based on the clustering of the genotypes in hydroponics and soil culture systems, we found that similar genotypes were commonly clustered either in the small-root or in the big-root group, indicating that the hydroponics system can be employed for a large-scale root phenotyping. Our results further revealed that the root biomass positively contributes to increased seed yield in sesame, based on multi-environmental trials. By comparing the root transcriptome of two contrasting genotypes, 2897 differentially expressed genes were detected and they were enriched in phenylpropanoid biosynthesis, starch and sucrose metabolism, stilbenoid, diarylheptanoid and gingerol biosynthesis, flavonoid biosynthesis, suggesting that these pathways are crucial for sesame root growth and development. Overall, this study sheds light on the diversity of sesame root system and offers the basis for improving root traits and increasing sesame seed yield.