复合发酵剂馒头和单一酵母馒头风味物质比较

采用同时蒸馏萃取(simultaneous distillation extraction,SDE)提取,气相色谱-质谱联用(gas chromatography-mass spectrometry,GC-MS)检测复合发酵剂馒头和单一酵母馒头的风味物质成分,结果表明：从复合发酵剂馒头中检测到36种化合物,包括对风味物质贡献较大的醇类、酯类、羰基化合物等。从单一发酵剂馒头中检测到16种化合物。研究结果表明,复合发酵剂馒头的风味物质不仅种类多,而且相对含量也明显高于酵母馒头。     

Effects of 1‐MCP applied postharvest on epicuticular wax of apples (Malus domestica Borkh.) during storage

BACKGROUND: Certain apple cultivars develop a greasy feel when overripe. Treating fruits with the ripening inhibitor 1‐methylcyclopropene (1‐MCP, SmartFresh^™) reduces fruit greasiness. This study examines the nature of this phenomenon. ‘Royal Gala’ apples were treated with 1‐MCP at 1.0 µl L⁻¹ following harvest. Periodically, during storage at − 1 °C for up to 6 months, fruits were evaluated for internal ethylene concentration, fruit epicuticular wax morphology (using scanning electron microscopy) and non‐polar organic solvent‐extractable (NPOSE) wax constituents of the cuticle (using gas chromatography/mass spectrometry). RESULTS: In 2004, 1‐MCP strongly inhibited internal ethylene production; however, total weight of NPOSE wax during storage was unaffected by treatment. In 2005, several wax constituents present in both ‘Autumn Gold’ and ‘Royal Gala’ showed differences during storage. In 2006, cuticular wax constituents comprising 80% of the total from ‘Royal Gala’ showed no treatment differences. Although several minor constituents did exhibit differences within treatment and sampling date, these did not appear sufficient to cause the subtle differences in surface wax morphology. CONCLUSION: 1‐MCP strongly inhibited ethylene production and delayed development of certain wax constituents thought responsible for fruit greasiness during cold storage. Subtle differences in surface wax morphology appeared unrelated to wax production. Published in 2008 by John Wiley & Sons, Ltd.     

Changes in phenolic compounds and Rancimat stability of olive oils from varieties of olives at different stages of ripeness

BACKGROUND: Recently, diets rich in natural foods and food‐derived components, such as phenolic compounds, have received a great deal of attention because they are perceived as ‘safe’ and ‘non‐medicinal’. In fact, some are known to function as chemopreventive agents against oxidative damage, cerebrovascular disease, and aging. RESULTS: Phenolic compounds, natural antioxidants present in virgin olive oil, play an important role in oil quality by contributing significantly to protecting oil stability against oxidation. In addition, polyphenols are the main contributors to olive oil bitterness, astringency and pungency. The data were fit by linear regression, giving Rancimat stability (h) = 0.18× Total polyphenols (mg L^?1) in the virgin olive oil. CONCLUSIONS: The practice of harvesting ripe olives as soon as possible to produce oils of high phenolic contents and thus high oxidative stability implies bitter and piquant oils, this being admissible for oils of some varieties but detrimental to others appreciated in the market for being more fruity and sweeter. Copyright © 2010 Society of Chemical Industry     

牛乳经酵母菌和乳酸菌发酵生产低醇乳酒的研究

用鲜牛乳为主要原料,添加蔗糖和营养素等辅料,经酵母和乳酸菌混合接种发酵,生产出低醇乳酒。通过对2种菌发酵方式的选择、协同性发酵实验、乳酸菌接种量和营养素的添加、发酵条件优化及发酵过程分析和发酵终点确定的研究,结果表明,当蔗糖添加量为10%时,乳酸菌的接种量为1%;牛乳酒生产的最佳配方及工艺条件是牛乳用量30%,营养素添加量70mg/L,酵母接种量8%,温度28℃。经生产性实验,在总发酵时间28h,乳酒产品酒精含量达到2·02%,呈乳白色,状态均匀,泡沫细腻,乳香、酒香和谐一体。     

Chemical Evaluation of Musa ‘Bhimkol’ as a Baby Food

The edible pulp of Musa ‘Bhimkol’ was analysed for certain organic compounds and mineral nutrients at two stages of development of the fruit to evaluate it as a baby food. Energy value and carbohydrate concentration increased substantially as the fruit ripened so that 16.8% of the energy requirement (recommended daily allowance, RDA) for six-month-old infants would be met by 100 g of the fresh pulp. Although vitamin C content decreased at maturation, 7% of the RDA would be provided by 100 g fresh pulp. The fruit was found to be very rich in macro- and micronutrients, and 100% of the six-month infants RDA for K, Mn, Zn and Se would be satisfied with 100 g of fresh pulp. This amount of pulp would also provide 86%, 57%, 24% and 12% respectively of the Mg, Cu, Fe and P RDA. P and Mg were found to be more highly concentrated in the ripe than in the unripe fruit whereas the reverse was the case for Ca and Se. Aspartic acid, glutamic acid and leucine were the major amino acids in the ripe fruit and respectively constituted 13.1, 12.5 and 7.9%, of the total. The concentration of essential and non-essential amino acids was much higher than that in a commercial banana. Twelve of the 17 amino acids analysed were more concentrated in the mature compared with the green fruit, and 11 of these were an order of magnitude higher than in M paradisiaca L banana. The results of the present study demonstrate that Musa ‘Bhimkol’ is a nutritious baby food.     

Influence of fast and slow distillation on ethyl carbamate content and on coefficient of non‐alcohol components in Brazilian sugarcane spirits

Ethyl carbamate is an impurity present in distilled beverages. Given the risk of it being a carcinogenic substance, Brazilian legislation has determined that its presence in distilled beverages, such as ‘aguardente’ and ‘cachaça’ (two types of sugarcane spirits), should be limited to a maximum of 150 µg/L. Ordinary spirits usually contain variable amounts of ethyl carbamate, although in lower concentrations than the maximum determined by law. The finding that commercial spirits had a much lower concentration of this impurity (around 50 µg/L) led the authors to research the reasons for the differences, and these are explored in this paper, with a focus on the speed of the distillation process and its influence on the spirit's composition. The team conducted research in a sugarcane distillery producing ‘aguardente’ using a simple pot still and measured the influence of fast and slow distillation on the presence of ethyl carbamate and non‐alcohol components in the process. The results demonstrated that the speed of distillation was proportionally related to the concentration of ethyl carbamate and secondary components in the beverage's composition. Copyright © 2012 The Institute of Brewing & Distilling     

Determination of 4‐ethylcatechol in a Merlot wine using sensory evaluation and the electronic tongue

The objective of this study was to determine the influence of 4‐ethylcatechol (4‐EC) on the sensory profile of Brettanomyces‐contaminated Merlot wine and evaluate electronic tongue discrimination. Using sensory evaluation panels, the consumer detection threshold (DT) and the consumer rejection threshold (CRT) of 4‐EC were determined in Merlot containing 493, 714, 1035 and 1500 μg L^?1 4‐EC. The DT of 4‐EC in Merlot was 823 μg L^?1, while the CRT was 1323 μg L^?1. The electronic tongue discriminated index (DI = 82%) among the samples, with hierarchical clustering showing a clear distinction between the control sample and the spiked samples. The lowest concentration distinguished by the electronic tongue was 493 μg L^?1, a lower value than the sensory threshold determined. These findings suggest that for the detection of 4‐EC in Merlot, the e‐tongue may be more sensitive than some consumers and the e‐tongue may be a suitable methodology for detection of subthreshold concentrations of chemical compounds in wine.     

New vectors for combinatorial deletions in yeast chromosomes and for gap-repair cloning using ‘split-marker’ recombination

New tools are needed for speedy and systematic study of the numerous genes revealed by the sequence of the yeast genome. We have developed a novel transformation strategy, based on ‘split-marker’ recombination, which allows generation of chromosomal deletions and direct gene cloning. For this purpose, pairs of yeast vectors have been constructed which offer a number of advantages for large-scale applications such as one-step cloning of target sequence homologs and combinatorial use. Gene deletions or gap-repair clonings are obtained by cotransformation of yeast by a pair of recombinant plasmids. Gap-repair vectors are based on the URA3 marker. Deletion vectors include the URA3, LYS2 and kanMX selection markers flanked by I-SceI sites, which allow their subsequent elimination from the transformant without the need for counter-selection. The application of the ‘split-marker’ vectors to the analysis of a few open reading frames of chromosome XI is described.     

Reduction in hydroxymethylfurfural content in ‘churros’, a Spanish fried dough,by vacuum frying

This work explores the advantages of vacuum frying of ‘churros’, a Spanish dough pastry, compared to standard deep‐fat frying. Oil uptake, texture change, colour development, nonenzymatic browning and hydroxymethylfurfural (HMF) concentration were analysed at different frying conditions. The results obtained during vacuum frying at 100, 120 and 140 °C and 21 kPa were compared with those obtained at atmospheric pressure at 140 and 180 °C. For the same final water content, the vacuum fried ‘churros’ showed no significant differences in the fat uptake compared to those fried at atmospheric pressure (P > 0.05). However, the vacuum fried dough had a much crunchier texture. The evolution of the CIELab a* coordinate and the browning measurement at 280 nm show that vacuum frying is able to slow down the development of browning tones. Furthermore, products can be obtained with an HMF content <1 mg kg^?1 of dry dough.     

Detecting adulteration of Dendrobium officinale by real‐time PCR coupled with ARMS

The high commercial value of ‘Tiepi Fengdou’ presents the constant risk of adulteration with cheaper Dendrobium products. Therefore, a novel method, combining SYBR Green II‐based real‐time PCR (rt‐PCR) with amplification refractory mutation system (ARMS), was established. By performing the diagnostic rt‐PCR assay, a 109‐bp fragment was specifically amplified from the internal transcribed spacer region of D. officinale. The difference between the average cycle threshold (C_t) value of ‘Tiepi Fengdou’ (20.48) and the mean of those of all reference Dendrobium products (31.83) was statistically significant (P < 0.001). The results indicate that the established system can be able to rapidly and unequivocally discriminate ‘Tiepi Fengdou’ from its adulterants.     

A rapid non‐destructive method for fish quality control by determination of smell intensity

The ‘Cosmos’ instrument (Japan) was applied to the evaluation of fish quality in six species of different origins, by determination of smell intensity. Pond‐raised fish (trout, carp, silver perch, tilapia, barramundi) were stored in ice for 4–5 weeks and frozen/thawed mackerel was kept at room temperature for 74 h. The fish quality was examined by organoleptic assessment, by determination of smell intensity and by tests of the chemical (total volatile basic nitrogen, hypoxanthine and histamine) and dielectric (Torrymeter) properties. Strong correlation was found between the organoleptic and ‘Cosmos’ results, whereas the data from the chemical and Torrymeter analyses were relatively poorly correlated with the sensory evaluation and ‘Cosmos’ data. Thus the application of the ‘Cosmos’ instrument for objective quantitative evaluation of fresh and chilled fish quality by determination of smell intensity seems practicable. The ‘Cosmos’ instrument is hand‐held and portable as well as being rapid and non‐destructive in operation; therefore it could be used for evaluation of fresh and chilled fish in the field and on board fishing vessels. Copyright © 2003 Society of Chemical Industry     

Effects of a chitosan‐based coating with ascorbic acid on post‐harvest quality and core browning of ‘Yali’ pears (Pyrus bertschneideri Rehd.)

BACKGROUND: Chitosan (CTS), as an ideal coating material, has been used for post‐harvest treatment of fruits and vegetables. The effects of coating with 1.5% CTS, alone or combined with 10 mmol L^?1 ascorbic acid (AsA), on post‐harvest quality and core browning (CB) incidence in ‘Yali’ pears during storage at room temperature (25 ± 1 °C) were investigated in this study. RESULTS: It was found that both CTS coating and CTS + AsA coating delayed the increase of weight loss, retained greater firmness, total soluble solids and titratable acidity content than controls; coatings decreased respiration rate and membrane permeability, and also effectively inhibited CB after 60 days of storage. Compared with CTS coating alone, CTS + AsA coating increased these beneficial effects and also helped to retain a much higher AsA content and the activities of antioxidative enzymes (superoxide dismutase, catalase and ascorbate peroxidase). CONCLUSION: The CTS coating has the potential to maintain post‐harvest quality and control CB which is the main problem in ‘Yali’ pears during storage. The CTS + AsA coating has more effective application in this study, which could not only be due to reducing the respiration rate and inhibiting the senescence process, but also to increasing the antioxidant capability of the fruit. Copyright © 2008 Society of Chemical Industry     

在红枣汁中乳酸菌、酵母菌单一及偶联发酵特征物质差异分析

该试验以红枣为原料,研究乳酸菌、酵母菌单一及偶联发酵对枣汁总糖、总酸、总酚、黄酮和酒精含量的影响,使用液相色谱-质谱联用（Liquid Chromatograph-Mass Spectrometer,LC-MS）技术进行游离型酚酸差异分析,气相色谱-离子迁移谱联用（Gas Chromatography-Ion Migration Spectrum,GC-IMS）技术进行挥发性有机物差异分析。结果表明,原枣汁无论是单一菌种发酵还是混合菌种发酵,总糖、黄酮含量降低,总酸、总酚含量、酒精度均增加,反式阿魏酸、4-羟基苯甲酸、氢化肉桂酸、香草酸、苯甲酸、丁香酸增加;酵母菌发酵枣汁总酚、黄酮、酒精度、苯丙氨酸、儿茶素、表儿茶素、丁香酸 、芥子酸含量均高于乳酸菌发酵枣汁,总酸含量低于乳酸菌发酵枣汁;经混菌偶联发酵,糖类物质降解效率、产酸效率、总酚生成率、黄酮留存率以及产酒精效率更高;游离型酚酸反式阿魏酸、反式肉桂酸、香草酸、没食子酸、对香豆酸、苯甲酸、原儿茶酸、咖啡酸、丁香酸较单菌发酵样品高;挥发性成分53种,包括11种醇类化合物、9种酯类化合物、8种酮类化合物、8种醛类化合物、2种酸类化合物、2种吡嗪吡嗪类化合物,混菌发酵样品中风味物质酯类、醇类、醛类分别占17.2%、58.2%、和1.3%,酯类和醛类显著高于乳酸菌发酵样品、酵母菌发酵样品及原枣汁,香味浓烈,因此采用酵母菌、乳酸菌混合发酵,可以有效地增强发酵枣汁的品质,丰富口感,该研究为推动混菌发酵在红枣酵素发酵生产行业的应用,提供相应的理论基础和科学实践依据。     

Compositional and degradative changes during the manufacture of dry‐cured ‘lacón’

The gross and mineral composition, the main physicochemical parameters, the protein extractability and the proteolytic (nitrogen fractions and free amino acids) and lipolytic (acidity index and free fatty acids) changes were studied throughout the manufacturing process of five batches of dry‐cured ‘lacón’, a traditional Spanish meat product made from the fore‐ham of the pig following a similar technological process to that of dry‐cured ham. The main compositional characteristics of this product are the high NaCl content and the low moisture content at the end of the curing process. The pH remained fairly stable (around 6) throughout the whole process and a fall in a_w was observed, reaching very low (0.767 ± 0.052) final average values. It was noted that 76% of the sarcoplasmic and 83% of the myofibrillar proteins became insoluble during the manufacturing process. The values of the different nitrogen fractions increased in a significant manner during manufacture, reaching low final values that indicate that ‘lacón’ undergoes a low level of proteolysis in comparison with other products manufactured by similar technologies. The high NaCl content and the intense dehydration suffered during the manufacturing process appear to be the principal causes of this reduced protein degradation. In accordance with the limited increase in the α‐amino acidic nitrogen during ripening, the total free amino acid content increased slightly but significantly from average values of 4371 mg kg^?1 dry matter in fresh pieces to average values of 13 020 mg kg^?1 dry matter in pieces at the end of the ripening process. The profile of free amino acids in the final product was similar to that observed by other authors in dry‐cured ham. The acidity of the fat increased by a factor of five. The final average values (49.9 g oleic acid kg^?1) were lower than those determined in dry‐cured ham, which indicates that ‘lacón’ undergoes less lipolysis during the ripening process than dry‐cured ham. C18 : 1, C18 : 2 and C16 were the most intensively released fatty acids during curing. The profile of free fatty acids in the end product was in agreement with that observed by other authors in dry‐cured ham. Copyright © 2003 Society of Chemical Industry     

不同类型丝状真菌发酵产酶性能比较及其混菌发酵性能研究

比较了实验室前期从福建红曲黄酒酿造用曲中分离及台湾生物资源研究及保存中心(BCRC)的不同丝状真菌菌株(黑曲霉AN19、黄曲霉AF20、米曲霉AO35、米根霉RO45、黑曲霉BCRC31494、黄曲霉BCRC31654、米曲霉BCRC30222和米根霉BCRC32229)的产酶性能,从中筛选出产液化酶、糖化酶和蛋白酶活力较高的4株菌株:黄曲霉AF20、米根霉RO45、黑曲霉BCRC31494和米曲霉BCRC30222。将此4株丝状真菌菌株分别进行单一和两两混合发酵糯米,研究其产酶及产糖性能。结果表明:接种纯种米根霉RO45到糯米培养基中,测得的液化酶活力和还原糖产量最高,然而整个发酵过程蛋白酶活力始终较低;米根霉RO45与米曲霉BCRC30222混合发酵,不仅保持较高的液化酶活力和还原糖产量,还能够显著提升发酵体系中的蛋白酶活力。本研究结果对于黄酒传统酿造工艺的改进和优良产酶菌株的筛选提供了重要的基础数据。     

Effect of the side chain size of 1‐alkyl‐pyrroles on antioxidant activity and ‘Laba’ garlic greening

Previous studies showed that 1‐alkyl‐pyrroles not only occur in fresh food products postulated as a natural antioxidant but also might be involved in garlic greening. In the present study, a series of 1‐alkyl‐pyrroles with different side chain size were synthesised to study the relationship of structure and antioxidative activity and their effects on ‘Laba’ garlic greening. The antioxidative activity of these compounds was evaluated by the method of scavenging ABTS˙ and DPPH˙. Results showed that increasing the size of R groups on the side chain, the antioxidative activity decreased gradually against the two radicals. The 1‐alkyl‐pyrroles generally exhibited stronger scavenging activities against ABTS˙ than DPPH˙. In contrast, their corresponding amino acids except for tyrosine showed almost no antioxidative activities while pyrrole exhibited much weaker activity as compared with the 1‐alkyl‐pyrroles, suggesting that the 1‐alkyl‐pyrroles donate H‐atom from pyrrole moiety rather than side chain to quench the two radicals. On the other hand, all 1‐alkyl‐pyrroles can turn newly harvested garlic green but to a different extent. All these results suggested that these pyrrole derivatives occurring in foodstuff played an important role in either protecting foodstuff from oxidation or acting on pigment precursors during ‘Laba’ garlic greening.