不同炒籽工艺对低芥酸浓香菜籽油风味的影响北大核心CSCD

为了研究不同炒籽工艺对低芥酸浓香菜籽油风味的影响,以低芥酸油菜籽为原料,研究入炒水分、炒籽温度、炒籽时间对低芥酸浓香菜籽油风味物质含量及感官品质的影响。结果表明:从低芥酸浓香菜籽油中共鉴定出65种挥发性风味物质;随炒籽温度上升、炒籽时间延长,低芥酸浓香菜籽油中呈现烤香味的杂环类物质总含量逐渐增加;随炒籽温度上升和入炒水分的增加,呈现刺激味的硫苷降解产物(含硫类化合物、腈类化合物)总含量逐渐增加;在感官上,低芥酸浓香菜籽油主要体现为烤香味、焦糊味,还能感知到腌菜味和刺激味;随炒籽温度升高,低芥酸浓香菜籽油中烤香味感官属性得分先上升后降低,150℃时得分最高,而焦糊味、腌菜味等感官属性得分逐渐升高;随炒籽时间延长,烤香味感官属性得分逐渐降低,焦糊味感官属性得分逐渐升高;随入炒水分增加,烤香味、焦糊味感官属性得分在一定范围内稳定波动。炒籽过程中一定的炒籽温度及增加水分能够明显提升消费者喜好度。     

Biochemical and toxicological studies on the effect of high and low erucic acid rapeseed oil on rats

Rats were fed on diets containing rapeseed oil, either containing low or high erucic acid content as well as the hydrogenated ones for 6 weeks. Body weight gain, biochemical and pathological parameters were investigated. The data showed high body weight gain for rats fed diets containing low erucic rape oil (LERo) compared with those fed either the high erucic rape oil (HERo), the hydrogenated or the partially hydrogenated oil diets. All rats showed non significant changes for total lipids, total cholesterol, GPT and GOT, except the partially hydrogenated rape oil diet which showed significant decrease for total cholesterol. Alkaline phosphatase however showed a significant decrease, while plasma phospholipids showed significant increase in rats fed on the hydrogenated oil diet. Triglycerides indicated non significant increase except in the group that received low erucic rape oil diet. Histopathological study showed changes in all tissues examined (liver and kidney).     

Influence of temperature and pressure on hydrogenation of low erucic acid rapeseed oil (Zephyr)

Low erucic acid rapeseed oil (Zephyr) was hydrogenated at 200, 170 and 140°C and pressure of 48 and 303 kPa. The hydrogenated oils were characterized by determination of the iodine value, trans-isomer content, fatty acid composition, dropping point and solid fat content. From the change in iodine value and trans-isomer content, the specific isomerization index (SII) was determined. The SII was generally lower at high pressure and low temperature. The hydrogenation reaction rate increased with temperature as well as pressure. Selectivity ratios for the hydrogenation reaction were more influenced by pressure than by temperature, the highest selectivity ratios were observed at the lower pressure.     

Variations in ascorbic acid content of gramineae during germination and the effect of β- and γ- radiation

The ascorbic acid content of three types of Gramineae, viz., Triticum vulgare, Hordeum vulgare and Zea mays (Nab El-Gamal and Beladi), is given and also the average variations in the seeds during germination are shown. The effects on the seedlings of β-irradiation emitted from small doses of radioactive H₃³²PO₄ as well as by irradiation with 131 I, are investigated.     

Effect of mild heat treatment on the nutritive value of low glucosinolate–low erucic acid rapeseed meals

Heat treatment (dipping seeds in boiling water) of two cultivars of Brassica napus, 1788 and 940, low in glucosinolates and erucic acid produced improved weight gains and lower thyroid weights in rats who received these meals as the only source of protein. Unheated cv 940 meal on autolysis did not produce detectable amounts of nitriles and increased weight gains were observed in rats ingesting the autolysed meal. Steaming of unheated meal similarly gave increased weight gains and the effects of steaming and autolysis were additive. The rates of weight gain of rats who ingested unheated and heated meals were different for the first ten days of feeding the meals but subsequently were similar, indicating the possibility of palatability factor(s) or another appetite depressing factor(s) being present in unheated meals. Trypsin inhibitor activities determined for various rapeseed meals were low as compared to soybean. Chlorogenic acid and myrosinase, both known constituents of rapeseed, did not show any trypsin inhibitor activity. In vitro digestibility measurements with pancreatin and pepsin didnot show significant differences between heated and unheated meals nor did an in vivo digestibility trial, although the rats consumed less of the feed containing unheated meal.     

Deterioration of β-carotene in certain hydrogenated fats. II.—Products of β-carotene deterioration and nature of the green pigment

The non-saponifiable fraction from a sample of β-carotene-hardened palm kernel oil which had developed a green discoloration has been examined. A number of β-carotene oxidation products were found and these included a number of β-carotene epoxide derivatives. A compound thought to be β-apo-3-carotenal was also found, but the apo-2- and apo-4-carotenals were not present in more than trace amounts. A major component was similar to, but not identical with, mutatochrome (β-carotene 5,8-epoxide). It is suggested that the green discoloration of the carotenised fat was due to oxidation of β-carotene to epoxide derivatives by traces of peroxyacids and the conversion of these epoxides into green-blue ionised forms by the action of an acidic material present in the fat.     

Phytate content is reduced and β‐glucanase activity suppressed in malted barley steeped with lactic acid at high temperature

The effect of different steeping conditions on phytate, β‐glucan and vitamin E in barley during malting was studied by a full factorial experiment with three variables (steeping temperature, barley variety and steeping additions). Addition of lactic acid to the steeping water induced a reduction of phytate during steeping and germination, especially in combination with the high steeping temperature (48 °C). Furthermore, lactic acid and high temperature steeping inhibited β‐glucanase development, resulting in a well‐preserved β‐glucan content after germination. When steeping was conducted without addition of lactic acid, the low steeping temperature (15 °C) promoted development of both phytase and β‐glucanase activity during germination. A slightly higher level of tocopherols and tocotrienols was observed in samples steeped at 15 °C than in samples steeped at 48 °C. However, addition of lactic acid reduced the amount for both temperatures. When lactic acid bacteria were added to the steeping water none of the parameters studied differed from samples steeped with water only. The results show the possibility of combining phytate degradation with a preserved β‐glucan content during malting and can thus be of interest for development of cereal products with improved nutritional value. Copyright © 2004 Society of Chemical Industry     

冷冻结晶法和尿素包合法降低播娘蒿籽油中芥酸的研究

利用冷冻结晶法和尿素包合法分离播娘蒿籽油中的亚油酸和α-亚麻酸,降低其中的芥酸。先冷冻结晶处理,再尿素包合可减少尿素用量,分离效果好,亚油酸和α-亚麻酸的收率高。实验结果表明,当V脂肪酸∶W尿素∶V甲醇为1∶2∶4时,样品中亚油酸和α-亚麻酸的总含量达到了95%,而芥酸的含量小于1%,亚油酸和α-亚麻酸的收率为83.3%。     

β-carotene content in sweet potato varieties from China and the effect of preparation on β-carotene retention in the Yanshu No. 5

To compare the β-carotene contents in different Chinese sweet potato (SP) varieties and to choose a variety of SP rich in β-carotene for the study of the effect of processing methods on β-carotene retention, β-carotene in thirteen varieties of sweet potato from China was measured by HPLC. The results showed that β-carotene contents were significantly correlated with SP flesh colours, with the orange-red fleshed SP varieties being higher in β-carotene.β-carotene contents in SP were affected by many factors, and this was demonstrated using the variety of Yanshu No.5, showing that the β-carotene contents in SP grown in different farming sites in the same area ranged from 53.2 to 84.3 mg kg^− 1 fresh weight. Moreover, β-carotene distributes unevenly in one SP root, with highest concentrations in the core. The β-carotene content was positively related to the root size.Five processing methods including boiling, steaming, microwave cooking, frying, and post steam-drying were simulated in the study to check their effects on the true retention of β-carotene in SP. Compared to boiling, steaming resulted in much more loss of β-carotene and microwave cooking resulted in the biggest loss of β-carotene among the five processing methods.

Industrial relevance

Orange-fleshed sweet potato can be prepared for sale and consumption, using methods that protect the β-carotene content. This can aid in promoting sweet potato as a staple food as well as a snack food for supplying vitamin A for both rural and urban populations. Prepared orange-fleshed sweet potato can contribute to alleviating vitamin A deficiency in China as well as other low-income countries.     

Per-O-methylated α- and β-CD: Cyclodextrins with Inverse Hydrophobicity

The investigation focuses on the computer-aided generation of the molecular geometries, contact surfaces, and lipophilicity patterns of per-O-methylated α-CD ( 1 ) and its β-CD homolog 2 , and compares them with their parent non-substituted cyclodextrins. The molecular geometries, compared via statistical analysis of crystal structure data available, reveal 1 and 2 to be considerably more flexible than α-and β-CD, allowing wide variations in the tilting of the glucose units relative to the macrocyclic ring axes. The comparative evaluation of their contact surfaces not only discloses a substantial increase of the torus heights upon per-O-methylation (from ∼8.0Å in α- and β-CD, to → 11.1Å in 1 and 2 ), but also an enlargement of their cavity areas by 40% (+35Ų for α-CD → 1 ) and 70% (+75Ų for β-CD → 2 ), respectively. The hydrophobic characteristics of 1 and 2 , emerging from the molecular lipophilicity patterns (MLPs) generated and projected onto the contact surfaces in color-coded from, are inverse to those for α- and β-CD: the most hydrophobic surface regions of 1 and 2 are located at the torus rims made up by the 2-OMe and 3-OMe groups at one side, and the 6-CH₂OMe moieties at the other, with a hydrophobic „band”︁ wrapping around the outside of the macrocycles; these „exo-lipophilic”︁ topographies are opposed by pronouncedly hydrophilic central cavities. A variety of experimental findings can be rationalized on the basis of the opposite lipophilicity profiles of the CDs and their permethylated analogs, such as for example the opposite orientation of benzaldehyde, p-nitrophenol, and 3-iodopropionic acid in the cavities of α-CD and of 1 . Thus, the notion is substantiated that the operation of dispersive interactions between guest and CD-host cavities play a more dominant role in inclusion complex formation than hitherto appreciated.     

Comparative study of enzymatic hydrolysis of α/β- and γ-gliadins

Enzymatic hydrolysis of proteins and fractionation of hydrolysates is a route of diversifying their functional properties. Chymotryptic hydrolysis of different sulphur-rich gliadins (α/β- and γ-types), major wheat storage proteins, was studied. The peptides formed in the course of digestion were characterised by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate (SDS-PAGE) and reversed-phase high performance liquid chromatography (RP-HPLC). With reference to previous work, a general scheme of degradation was assessed for γ-gliadins. Limited hydrolysis released two types of polypeptides, comprising respectively the repetitive and the non-repetitive moieties of the protein. In spite of strong sequence homologies between the two groups of sulphur-rich gliadins, it was not possible to prepare similar peptide fractions from α/β-gliadins. They were more resistant to hydrolysis and the region where the two domains merge appeared inaccessible to chymotrypsin. Restricted accessibility of cleavage sites was attributed to the less expanded conformation of α/β-type than γ-type gliadins. A first step of scaling-up was performed. This offers opportunities to prepare functional peptides from wheat storage proteins.     

Concentration‐dependent antioxidant activities of conjugated linoleic acid and α‐tocopherol in corn oil

BACKGROUND: Antioxidants prevent rancidity (lipid peroxidation) and natural antioxidants, e.g., α‐tocopherol, likely provide additional value to oil‐based food products because of their health benefits. Conjugated linoleic acid (CLA) has potential health benefits and may exhibit antioxidant properties. The main aim of this study was to compare the antioxidant efficacy of α‐tocopherol, trans‐10, cis‐12‐CLA and cis‐9, trans‐11‐CLA (in graded concentrations) added to antioxidant‐stripped corn oil. RESULTS: As compared to α‐tocopherol, both CLA isomers displayed significant inhibition of corn oil lipid peroxidation induced by copper. Inhibition of thiobarbituric acid reactive substances (TBARS) were CLA concentration dependent for both isomers but with significant inhibition occurring at 0.1 and 1 ppm of CLA isomers or α‐tocopherol, respectively (P < 0.05). Graded concentrations of α‐tocopherol, and for both CLA isomers and time, had significant effects on TBARS formation (P < 0.0001). There were significant effects in interactions between graded concentrations and time for both CLA isomers (P < 0.0001) but not for α‐tocopherol (P > 0.05). CONCLUSION: CLA compounds could serve as useful food antioxidants and provide additional value because of their potential bioactivity in disease prevention. Copyright © 2007 Society of Chemical Industry     

Isolation of obligate anaerobic rumen bacteria capable of degrading the neurotoxin β‐ODAP (β‐N‐oxalyl‐L‐α,β‐diaminopropionic acid) as evaluated by a liquid chromatography/biosensor analysis system

Six pure strains of obligate anaerobes capable of degrading the toxin β‐N‐oxalyl‐L ‐α, β‐diaminopropionic acid (β‐ODAP) contained in grass pea (Lathyrus sativus) have been isolated from cow rumen. The new isolates were identified as Megasphaera elsdenii (five different genotypes) and Clostridium bifermentans using 16S rDNA analysis. The β‐ODAP degrading efficiency of the isolates was evaluated by measuring the amount of β‐ODAP in the growth medium, which contained β‐ODAP as the only carbon source, before and after incubation with the microbes. The method of analysis was liquid chromatography employing bioelectrochemical detection. The biosensor is based on co‐immobilising two enzymes, glutamate oxidase (GlOx) and horseradish peroxidase (HRP), on the end of a spectrographic graphite electrode. β‐ODAP is oxidised by GlOx to form H₂O₂, which in turn is bioelectrocatalytically reduced by HRP through a mediated reaction using a polymeric mediator incorporating Os^{2 + /3+} functionalities rapidly shuttling electrons with the electrode_giving rise to the analytical signal. On the basis of this analysis system, the new isolates are capable of utilising β‐ODAP as sole carbon source to a maximum of 90–95% within 5 days with concomitant increase in cell protein. Copyright © 2005 Society of Chemical Industry