元蘑游离必需氨基酸的测定

利用反相高效液相色谱法对元蘑游离必需氨基酸进行测定,结果表明元蘑游离氨基酸中含有7种必需氨基酸,色氨酸含量最高,达到1.56 mg/g,但缺乏蛋氨酸.     

CHANGES IN FREE AMINO ACIDS AND BIOGENIC AMINES DURING RIPENING OF FRESH AND FROZEN SARDINE

A study was carried out on the evolution of free amino acids and biogenic amines throughout the ripening process of fresh and frozen sardine. The effect of the level of fish gutting was also followed. During ripening a general increase of free amino acids content was observed in all samples. Histidine was the exception to this trend and decreased throughout the processing period. On the basis of the ratio of basic/acidic amino acids, as an indicative of the ripened state, the fresh nobbed sardine ripened faster than the gutted fish. During the course of ripening a considerable increase in biogenic amines and particularly histamine occurred until the 20th day in products from fresh fish. The maximum histamine content allowed in ripened fish products in the European Union (400 mg/Kg) was never attained in this period. A general decrease in most amines was observed by the 240th day of ripening. Tyramine behaves differently and increased in the same period. The samples prepared with frozen fish consistently showed the lowest amine values throughout the ripening period. It seems that freezing has a good effect on the final quality of ripened products as it could decrease the bacterial activity responsible for biogenic amine formation.     

CHANGES IN FREE FATTY ACID AND DIACYLGLYCEROL COMPOUNDS IN SHORT-RIPENING DRY-CURED SAUSAGE

A study on lipolysis of Southern Italy short-ripened dry-cured sausages manufactured without and with starters was carried out. Samples were submitted to microbiological and chemical analysis during drying and ripening, whereas sensory analysis was performed at the end of the ripening. The starters, addition caused the inhibition of the Enterobacteriaceae. An increase of free fatty acids (FFAs) and diacylglycerols (DAGs) during the ripening was observed. The addition of starter did not affect FFA and DAG release. The DAG profile including 1,2- and 1,3-isomers was analyzed for the first time in dry-cured sausages. Oleic, linoleic and palmitic acids, and 1,2-, 1,3-palmitinolein, 1,2- and 1,3-diolein were the most abundant compounds in FFA and DAG, respectively. A decrease in the concentration of some 1,2-DAG and an increase of 1,3-OO and 1,3-OP species during the process was observed. Finally, the addition of starter cultures slightly influenced the sensory properties of sausages.

PRACTICAL APPLICATIONS

In this work the development and application of an analytical method for the determination of free fatty acids (FFAs) and diacylglycerols (DAGs) in sausages was achieved. DAGs are intermediate products of hydrolysis and also constitute a substrate for hydrolysis reactions leading to FFA release. These latter compounds undergo a series of reactions leading to the formation of low-molecular-weight products responsible for sensory properties of dry-cured sausages. Therefore, the assessment of these lipolysis products is a useful tool for evaluating the ripening process of dry-cured sausages.     

秋刀鱼蛋白酶解物的制备及氨基酸评价

采用正交实验法优化制备秋刀鱼蛋白酶解物的最适工艺条件，探讨了影响秋刀鱼蛋白酶水解的主要因素。实验表明，最适的酶解条件为：复合酶与风味酶之比为1：3，复合酶量为0．100g／25g鱼肉，酶解温度为50℃，酶解时间为7h。在此条件下，秋刀鱼蛋白水解度为45．5％，总游离氨基酸含量为1800．53mg／100mL。经高效液相色谱分析，在水解产物中约50％的氨基酸为具有较高营养价值的抗氧化活性氨基酸和支链氨基酸。     

SUBCUTANEOUS ADIPOSE TISSUE LIPOLYSIS IN THE PROCESSING OF DRY-CURED HAM

ABSTRACT The activities of subcutaneous adipose tissue lipases and esterases were assayed at different stages (0 to 15 months) in the processing of dry-cured ham. The formation of free fatty acids during the process was also determined. Maximal generation of free fatty acids occurred during the first 10 months. Simultaneously, the triglyceride content decreased while the diglycerides increased during the aging period. Neutral and basic lipases showed maximal activity at the beginning of the process but only neutral lipase remained as the main enzyme responsible for the reported lipolysis during the drying ripening stages. Adipose tissue esterases showed excellent stability but the generation of volatile free fatty acids was negligible, suggesting a minor role of these enzymes.     

CHANGES IN NITROGEN FRACTIONS AND FREE AMINO ACIDS DURING RIPENING OF SPANISH DRIED BEEF "CECINA"

The changes in nitrogen fractions (total nonprotein nitrogen -NPN-, amino acid nitrogen, peptide nitrogen and volatile basic nitrogen) and free amino acids during the ripening of "cecina" (a Spanish dried beef product) were tracked. The amount of total NPN, amino acid nitrogen and volatile basic nitrogen increased during processing, while peptide nitrogen decreased in the last stage. An increase was observed in all amino acids except taurine. In the final product, the most abundant free amino acids were leucine-isoleucine mixture, lysine and proline-methionine mixture. Taking into account the concentrations of the most abundant amino acids detected in cecina and the taste thresholds described for L-amino acids in water, it appears that several amino acids i.e. lysine, alanine, valine and glutamic acid, could contribute to the flavor of this meat product.     

RELATIONSHIPS BETWEEN MUSCLE TISSUE CHARACTERISTICS AND SENSORY QUALITIES OF DRY-CURED HAM

Forty dry-cured hams were identified at the end of 9 months processing. The Biceps femoris was analyzed for dry matter, pH, protein, lipids, acid value, hydroxyproline, Cl^-, pigment, glycogen, lactic acid and protein fractions, and average diameter and metabolic type of fibers. Sensory analysis involved color scoring on a whole slice of ham; assessment (by sniffing) of the acceptability on the semimembranosus of all 40 hams; and evaluation of odor, texture, taste and aroma on the biceps femoris of 26 hams. Among the traits under study, dry matter, glycogen, lactic acid, Cl^- and pH appeared as the most important determinants of sensory qualities of dry-cured ham. High levels of glycogen, lactic acid and Cl^- and low pH were associated with dry texture and high intensity of dry ham and cured meat aroma. The other components studied revealed scarce and generally low correlations with sensory traits.     

干腌羊火腿工艺过程蛋白质水解及其理化性状相关性研究

通过对羊火腿工艺过程中总氮、可溶性氮及非蛋白氮的分析研究,来确定其蛋白质水解与工艺过程产品水分、NaC1含量及温湿度条件的相关性;结果表明:工艺过程中非蛋白氮的变化与工艺过程温度和产品水分的降低、温度和NaG1含量的提高呈正相关,且蛋白质在工艺过程中发生了持续降解.成品火腿的蛋白质降解指数在2～7未间.     

CHANGES IN SUGARS AND AMINO ACIDS DURING PARBOILING OF RICE

ABSTRACT Parboiled brown rice contained considerably more reducing sugars (RS) but less sucrose and free amino acids (FAA) than raw brown rice. On milling, there was considerably loss of sucrose and FAA from raw rice, but very little from parboiled rice; reducing sugars changed little in either. Processing conditions affected the contents of sugars and FAA. Maximum increase in RS and decrease in sucrose content occurred after soaking at 60°C. Controlled incubation of rice flour, intact grain, separated germ and degermed rice in water showed that considerable changes in sugars and FAA occurred in all cases, the magnitude depending on the circumstances, but a greater part of the sugars leached out into the water during soaking.     

PROPERTIES OF DRY-CURED HAM: TEMPERATURE AND pH INFLUENCE DURING SALTING STAGE

The influence of pH and temperature upon color properties, during the salting stage of 11 days for the dry-cured ham process was studied. Semimembranosus, Semitendinosus and Biceps femoris muscles were studied and each muscle was divided in three sections (outer, middle and inner). The parameters under study were: moisture, salt concentration, residual nitrite level, CIELAB and reflectance ratio (R650/R570). Neither temperature nor pH affected any parameter analyzed (P>0.05). Only Semimembranosus (and its outer zone) showed differences (P < 0.05) for moisture and salt concentration. A concentration gradient between muscles and Semimembranosus zones was found for residual nitrite level. Lightness, yellowness and chroma showed differences (P<0.01) for Semimembranosus muscle and its outer zone. Redness and reflectance ratio R650/R570 were not different (P>0.05) between muscles and zones. Only the Semimembranosus muscle was different (P<0.01) for hue. Semimembranosus and Biceps femoris zones were different (P<0.01 and P<0.05 respectively) for this parameter.     

THE MARGARET JONES MEMORIAL LECTURE AMINO ACIDS IN MALTING AND BREWING

Margaret Jones' researches into the role of amino acids in the biochemistry of malting and brewing are reviewed.     

QUANTITATIVE GAS CHROMATOGRAPHIC ANALYSIS OF AMINO ACIDS IN BEER AND WORT

Amino acids present in beer and wort samples were isolated using Dowex 50W-X8 ion exchange resin. These acids were converted to N-trifluoroacetyl methyl esters and were separated on a 10 ft. x 1/4 in. copper column packed with 3/4% Carbowax 1540 and 1/4% NPGS on Chromosorb W. Complete separation and quantitative estimation was obtained for eleven amino acids: valine, alanine, isoleucine, leucine, glycine, proline, aspartic acid, threonine, methionine, glutamic acid, and phenylalanine. Standards of the acids showed a relative standard deviation of 4% and less for nine acids while threonine and methionine gave deviations of 9% and 15% respectively. The other naturally-occurring amino acids did not interfere with the separation of the above eleven. Amino acid assimilation data is presented along with other beer and wort analyses.     

UPTAKE OF AMINO ACIDS IN BOTTOM FERMENTATIONS

The net uptake of amino acids in full-scale brewery fermentations with a strain of Saccharomyces carlsbergensis at 8–9° C. has been followed by analysing amino acids in fermenting wort and beer. The amino acids are usually taken up very incompletely and their uptake follows a certain order, not very different from that observed by British authors using top yeast fermenting at 15° C. The order is not quite constant, however; particularly the uptake of arginine and of ammonia are subject to variations. The amino acids can be divided, according to their rate of absorption and degree of utilization, into three clear-cut groups. The results suggest that it is the system allowing entry of amino acids into the cell that is of prime importance and that this is not capable of regulating the uptake to the demand of amino acids as building blocks for yeast protein. The results are considered in the light of recent investigations on amino acid permeases of yeast, and the metabolic roles of the most rapidly absorbed amino acids, serine, asparagine, glutamine, and threonine, are discussed.