Search

This study investigated the effect of fermentation by Lactobacillus plantarum CGMCC 14177 strain on physicochemical properties and morphological characteristics of potato starch. The maximum total amylase and α-amylase production of L. plantarum CGMCC 14177 were 286.8 and 208.1 U/g, respectively. Fermented granules clearly exhibited pocked and dimpled surfaces. The granule properties changed to have a 1.9% increase in relative crystallinity. Overall the starch changed to have slight increases in onset and peak temperature, but resulted decreases of conclusion temperature and enthalpy. Fermentation decreased peak viscosity and breakdown value, while increased trough viscosity, final viscosity, and setback. Further analysis showed that fermentation increased the gel hardness and chewiness of the potato starch, but made little differences in the springiness, cohesiveness and resilience. Collectively, these results provide insight on how Lactobacillus strains can be used to modify the physicochemical properties of potato starch in ways that extend its use in industrial applications.

Wheat germ oil (WGO) is rich in highly concentrated nutrients, especially vitamin E and polyunsaturated fatty acids. In this study, changes in oxidative stability, bioactive components, volatile compounds, and antioxidant capacity of WGO extracted from wheat germ roasted at 180 °C for 0–20 min were investigated. In general, antioxidant capacity and oxidative stability of WGO increased with roasting. Compared to oil from unroasted wheat germ, oil from wheat germ roasted for 20 min demonstrated the highest total phenolics, but a slight reduction in total tocopherols and β-carotenoids content. Fatty acid profiles were not affected, whereas hydroxymethylfrufural (HMF) content increased significantly, suggested the extent of Maillard reaction increased significantly with roasting. Among volatiles, esters such as n-butyl acrylate and acids such as hexanoic acid prevailed in WGO from unroasted wheat germ. However, after roasting, the levels of these compounds decreased or disappeared and furfurans, pyranes, pyrazines, and pyrroles with high odor activity became the most abundant.

With an interest to enhance the aroma of palm kernel oil (PKO), Pentopan mono BG (xylanase) was applied to alter the carbohydrates in palm kernels (PK) so as to modulate the formation of volatiles during kernel roasting. The result showed that a 1.3-fold increment of total soluble sugars was found in PK after Pentopan treatment, which promoted the generation of O-heterocyclic volatile compounds during kernel roasting. Overall, an increment of 1.5-, 1.4- and 1.3-fold of O-heterocyclic compounds were found in PKO derived from treated PK after light, medium and dark roasting, of which the elevation in furfural and 2-furanmethanol contents was the most obvious. Principal component analysis (PCA) clearly discriminated treated PKO with various kernel roasting degrees from that of control PKO on the basis of all aroma-active compounds; the aroma in PKO from treated, roasted PK was highly correlated with 2-[(methyldithio)methyl]-furan, 5-methyl-2-furancarboxaldehyde, 2-furanmethanol, 2,5-dimethylpyrazine and ethyl pyrazine. Sensory evaluation showed that PKO derived from medium roasted PK imparted more caramelic, nutty and smoky odor notes relative to the untreated PKO. This study suggests Pentopan pretreatment of PK followed by roasting may be a novel way to modulate PKO aroma and potentially widen its application.

Many studies showed that radio frequency (RF) holds great potential to control insects in grains, while a few more technical issues need to be addressed to further make this technology ready for industrial application. Therefore, the effect of RF heating rate on rice fissure ratio and broken rate, RF heating lethality on immature rice weevils, and RF disinfestation treatment on cooking and eating quality of milled rice was investigated in this study. Results indicated that RF heating rate had no significant influence on rice broken rate, while fast RF heating rate (>7.2 °C/min) had adverse effects on rice fissure ratio, and mild RF heating rate (

Solid-state fermentation with Yarrowia lipolytica was applied to palm kernels (PK) with the aim to modulate the aroma of palm kernel oil (PKO) obtained after kernel roasting. The results showed that, the metabolic activities of Y. lipolityca brought about significant changes to the volatile profile of obtained PKO either by providing thermal reaction reactants or by directly contributing aroma compounds. After fermentation, a decreased content in glucose (60%) while an elevated amount (7-fold) in free amino acids was found in PK, which further impacted the formation of volatile compounds by influencing the Maillard reaction and Strecker degradation during roasting. More Strecker aldehydes and N-heterocyclic compounds were formed in PKO derived from fermented PK especially after intensified roasting. In addition, the catabolism of Y. lipolytica imparted some distinct volatile compounds such as 2-phenylethanol to the obtained PKO. However, the lipase excreted by Y. lipolytica hydrolysed PK lipids and released 5-fold more free fatty acids in fermented PKO, relative to the blank and control PKO, which likely contributed to the off-flavor. On the basis of all volatile categories, principal component analysis (PCA) clearly separated the fermented PKO from the blank and control PKO, with light roasted, fermented PKO being correlated with acids, alcohols and aliphatic aldehydes; medium and dark roasted, fermented PKO tending to be dominated by pyrroles, pyrazines and furanones, which is in correspondence with sensory changes of PKO. This study demonstrated that combining fermentation with roasting could provide a novel way to modulate the volatile composition and aroma of PKO.

Rice husk is an important byproduct from the milling process of paddy rice, with a huge amount being produced worldwide each year. Silica exits abundantly in rice husk in an amorphous form. Hence, rice husk is a natural and renewable biomass source for extraction of silica and subsequently for manufacturing value-added, silicon-based materials. Currently, most rice husk is combusted directly to produce power or electricity resulting in the production of a large quantity of rice husk ash. Only a small amount of rice husk is used for extraction of silica in an industrial scale. This chapter presents a general review on the physicochemical properties of rice husk and rice husk ash, and their application as adsorbents in vegetable oil refining and removal of heavy metals. Different processing methods for production of silica and silica aerogel from rice husk ash, and the factors that influenced the physical and chemical properties of these products, are also addressed.

Palm kernel oil (PKO) is obtained from the seeds of oil palm (Elaeis guineensis Jackqu). In this study, volatiles and aroma-active compounds of PKO were studied by head-space solid-phase microextraction/gas chromatography/mass spectrometry/flame ionisation detector (HS-SPME/GC/MS/FID) and solvent-assisted flavour evaporation -gas chromatography/olfactometry/mass spectrometry (SAFE-GC/O/MS), respectively. An optimised HS-SPME sampling method was obtained for extraction at 60 °C for 40 min. With this method, the volatiles of PKO from palm kernels subjected to different roasting times (up to 30 min) at 180 °C were analysed. Totally 73 volatiles were found, including 19 O-heterocyclic compounds (16 furans and 3 pyrans), 15 N-heterocyclic compounds (10 pyrazines and 5 others), 15 carbonyl compounds (5 aldehydes and 10 ketones), 11 acids, 4 alcohols, 3 esters, 3 sulphur and 3 volatile phenols. With the extension of roasting times, peak areas of O-heterocyclic compounds, N-heterocyclic compounds, aldehydes and cyclic ketones increased significantly whereas those of acids, alcohols and esters generally decreased. Results of GC/O/MS showed that 2-nonanone, octanoic acid and methyl octanoate were the most aroma-active compounds in unroasted PKO, while in roasted PKO, the most active volatiles were ethyl pyrazine, 2-nonanone, 2-hydroxy-3-methyl-2-cyclopenten-1-one, maltol, 2,6-dimethylpyrazine, 2,5-dimethylpyrazine, 2,3-dimethylpyrazine, benzoic acid ethyl ester, octanoic acid, 5-methyl-2-furancarboxaldehyde and isomaltol.

Wheat germ is a good source for wheat germ oil, and it is a by-product with highly concentrated nutrients from the wheat flour-milling industries. In the present study, raw wheat germ was firstly heat-treated at 180 °C for 20 min in a fluidized bed dryer, and further roasted at 180 °C for different periods of time. Roasting influence on total phenolic content (TPC), antioxidant activities, and phenolic compositions of wheat germ were evaluated. The roasting process significantly increased the TPC and antioxidant activities including free radical scavenging against DPPH and ABTS radicals, FRAP, and ORAC. In particular, the wheat germ roasted at 180 °C for 20 min showed higher antioxidant activity than those roasted at 180 °C for 5 and 10 min. Three major phenolic acids, namely, ferulic, chlorogenic, and caffeic acid, and four main flavonoids, namely, schaftoside and its isomers or adduct of sinapic acid were identified by HPLC. In general, the content of individual phenolic compounds decreased with prolongation of the roasting time except for ferulic acid. The results suggest that the antioxidant activities of wheat germ can be enhanced by roasting, and the enhancement effect might be partially attributed to the formation of Maillard reaction products (MRP).

Germination is considered to be an effective process for improving the nutritional quality and functionality of cereals. In this study, changes of nutritional ingredients, antinutritional components, chemical composition, and antioxidant activities of buckwheat seeds over 72 h of germination were investigated, and the reasons for these changes are discussed. With the prolonged germination time, the contents of crude protein, reducing sugar, total phenolics, total flavonoids, and condensed tannins increased significantly, while the levels of crude fat, phytic acid, and the activity of trypsin inhibitor decreased. Phenolic compounds, such as rutin, vitexin, isovitexin, orientin, isoorientin, chlorogenic acid, trans-3-hydroxycinnamic acid, and p-hydroxybenzoic acid increased significantly during the germination process, which may be due to the activation of phenylalanine ammonialyase. The improvement of flavonoids led to significant enhancement of the antioxidant activities of germinated buckwheat. Germinated buckwheat had better nutritional value and antioxidant activities than ungerminated buckwheat, and it represented an excellent natural source of flavonoids and phenolic compounds, especially rutin and C-glycosylflavones. Therefore, germinated buckwheat could be used as a promising functional food for health promotion.

With an interest to enhance the aroma of palm kernel oil (PKO), Viscozyme L, an enzyme complex containing a wide range of carbohydrases, was applied to alter the carbohydrates in palm kernels (PK) to modulate the formation of volatiles upon kernel roasting. After Viscozyme treatment, the content of simple sugars and free amino acids in PK increased by 4.4-fold and 4.5-fold, respectively. After kernel roasting and oil extraction, significantly more 2,5-dimethylfuran, 2-[(methylthio)methyl]-furan, 1-(2-furanyl)-ethanone, 1-(2-furyl)-2-propanone, 5-methyl-2-furancarboxaldehyde and 2-acetyl-5-methylfuran but less 2-furanmethanol and 2-furanmethanol acetate were found in treated PKO; the correlation between their formation and simple sugar profile was estimated by using partial least square regression (PLS1). Obvious differences in pyrroles and Strecker aldehydes were also found between the control and treated PKOs. Principal component analysis (PCA) clearly discriminated the treated PKOs from that of control PKOs on the basis of all volatile compounds. Such changes in volatiles translated into distinct sensory attributes, whereby treated PKO was more caramelic and burnt after aqueous extraction and more nutty, roasty, caramelic and smoky after solvent extraction.

The aroma of palm kernel oil (PKO) affects its applications. Little information is available on how enzymatic modification of palm kernels (PK) affects PK and PKO aroma after kernel roasting.Celluclast (cellulase) pretreatment of PK resulted in a 2.4-fold increment in the concentration of soluble sugars, with glucose being increased by 6.0-fold. Higher levels of 1.7-, 1.8- and 1.9-fold of O-heterocyclic volatile compounds were found in the treated PK after roasting at 180 °C for 8, 14 and 20 min respectively relative to the corresponding control, with furfural, 5-methyl-2-furancarboxaldehyde, 2-furanmethanol and maltol in particularly higher amounts. Volatile differences between PKOs from control and treated PK were also found, though less obvious owing to the aqueous extraction process. Principal component analysis based on aroma-active compounds revealed that upon the proceeding of roasting, the differentiation between control and treated PK was enlarged while that of corresponding PKOs was less clear-cut. Celluclast pretreatment enabled the medium roasted PK to impart more nutty, roasty and caramelic odor and the corresponding PKO to impart more caramelic but less roasty and burnt notes.Celluclast pretreatment of PK followed by roasting may be a promising new way of improving PKO aroma. © 2017 Society of Chemical Industry.

This paper attempts to present a full picture of current situation and future trends of Chinese oil crop production. The total oil crop production remained broadly constant during 2011–2014. The top three oil crops are soybean, peanut and rapeseed, together accounting for more than 70% of total oil crop production. The area under cultivation and the production of peanuts will keep steadily increasing because most Chinese like its pleasant roasted flavor. Because of their high content in polyunsaturated fatty acids and the natural minor functional components in their oils, more attention is being paid to sunflower seed and rice bran. The diminishing availability of arable land and concern over the security of edible oil supplies is driving both a change in cultivation structure of crops and improvements in the efficiency of oilseed production in China.