Character impact odorants of high-heat skim milk powder isolated by simultaneous distillation-extraction.
To identify the character impact odorant of high-heat skim milk powder (HHSMP), a comparative study using ultrahigh-temperature (UHT) milk was performed. Aroma concentrate was prepared by column adsorption combined with simultaneous distillation-extraction. Aroma extract dilution analysis (AEDA) revealed 58 aroma peaks with flavor dilution (FD) factors ranging from 10 to 3000; from these, 41 compounds were identified and 7 compounds were tentatively identified (FD factor > or = 300). Among these HHSMP and UHT milk components, methyl 2-methyl-3-furyl disulfide and bis(2-methyl-3-furyl) disulfide, which appeared to be generated during the processing of each product, were identified. When the results of the AEDA of both samples were compared, it was considered that the characteristic aroma of HHSMP was not explained by a single compound but instead formed from a mixture of several types of compounds contained in common with the UHT milk. The contribution of these compounds to the aroma of HHSMP was confirmed by an aroma simulation experiment.
Characterisation of aroma profiles of commercial sufus by odour activity value, gas chromatography-olfactometry, aroma recombination and omission studies
Sufu is a solid-state fermented product made from soya beans. For the sake of quality control and regulation purposes, it is essential to be able to identify key odorants of various commercial sufus. To identify the aroma-active compounds in sufus, gas chromatography-olfactometry/aroma extract dilution analysis (GC-O/AEDA) was performed, and odour activity value (OAV) was estimated. The correlations between aroma profiles and identified aroma-active compounds were also investigated by principal component analysis. Results showed that 35 aroma-active compounds were detected through OAV calculation, while 28 compounds were identified by using GC-O/AEDA. Quantitative descriptive analysis revealed that aroma recombination model based on OAV calculation was more similar to original sufu in terms of aroma comparing to aroma recombination model based on GC-O/AEDA. Omission experiments further confirmed that the aroma compounds, such as ethyl butanoate, ethyl 2-methylbutanoate, ethyl hexanoate, (E,E)-2,4-decadienal and 2,6-dimethylpyrazine, contributed most significantly to the characteristic aroma of a commercial sufu.
Hapten inhibition of passive antidextran dextran anaphylaxis in guinea pigs. Role of molecular size in anaphylactogenicity and precipitability of dextran fractions.
High titred antidextran antisera have been raised in rabbits by prolonged immunization with soluble conjugates between isomaltose oligosaccharides or dextran mw 4,400 and bovine serum albumin in complete Freund’s adjuvant. Guinea pigs sensitized with such antisera exhibited anaphylactic shock on i.v. challenge with fractions of hydrolyzed B512 dextran. The severity of anaphylaxis depended on the amount of sensitizing antibody and the dose and molecular size of the challenging dextran fraction. In maximally sensitized animals, fractions of mw 3,600 or larger were anaphylactogenic and smaller molecular size fractions were nonanaphylactogenic. In submaximally sensitized animals, dextran fractions of mw 10,500 or less were foundnonanaphylactogenic. In addition, nonanaphylactogenic dextran fractions produced desensitization, i.e. protection from anaphylaxis due to subsequent or simultaneous injection of more high molecular and anaphylactogenic dextran fractions. When the molar ratio in a mixture of nonanaphylactogenic/anaphylactogenic fractions was about 7.6, protection was complete with reduction of mortality from 100 to 0%. A molar ratio of 1.9, corresponding to a 13-percent by weight admixture of nonanaphylactogenic dextran, still significantly reduced mortality from 100 to 50%. From the ability to form precipitates with antidextrans and to elicit anaphylaxis in sensitized guinea pigs, and from the absence of these properties, the approximate molecular size range of bivalent and monovalent dextran B512 fractions was found to correspond to mw 3,600 and mw 1,430, respectively. The practical applicability of hapten inhibition is discussed.