发酵香肠成熟过程中的生化变化

本文综合概述了有关发酵香肠在成熟过程中的一系列复杂生物化学变化及其影响因素,并提出今后有关发酵香肠的主要研究方向.     

Mango ripening: changes in cell wall constituents in relation to textural softening

Ripening of mango (Mangifera indica L., cv. Alphonso) fruit is characterized by a series of biochemical changes resulting in gradual textural softening. From unripe to ripe stage, the starch content came down from 18% to 0.1%; pectin from 1.9% to 0.5%; cellulose from 2% to 0.9% and hemicelluloses from 0.8% to 0.2%. Concomitantly, the total soluble solids increased from 7% to 20%, total soluble sugars from 1% to 15% and pH increased from 2.8 to 5.1. The increase in activity of several of the carbohydrate‐degrading enzymes, which resulted in solubilization of the various polysaccharide fractions, correlated with fruit‐softening phenomenon. Efficient distribution of ¹⁴C‐starch into glucose, fructose and sucrose revealed considerable sugar interconversions indicating active gluconeogenesis during mango fruit ripening. Copyright © 2005 Society of Chemical Industry     

Processing date varieties into pickles

Three major Saudi Arabian date varieties ( Nabbut Ghrein, Miskani and Hulwa ) were processed into pickles. Miskani dates were also pickled after 2 months' storage in brine. Titratable acidity, pH, total soluble solids, sucrose and reducing sugars were measured. All varieties processed fresh at different initial acidity levels and after different heat treatments were equally acceptable. Pickles produced from stored dates were less acceptable.     

Compositional changes during guava fruit ripening

Compositional changes of fruit pulp and peel during ripening of white- and pink-fleshed guava fruits were studied. The white and pink guava fruits exhibited a typical climacteric pattern of respiration. Fruit tissue firmness decreased progressively, in a similar manner, in both guava fruit types. Total soluble solids (TSS) and total sugars increased in pulp and peel of both guava types with decrease in flesh firmness. More increase in total sugars was observed after the climacteric peak of respiration. Reducing sugars and titratable acidity increased up to the full-ripe stage and then decreased. Ascorbic acid and phenolic compounds decreased continuously during ripening of the two types. The peel showed higher values of ascorbic acid, total protein and phenolic compounds than the plup. The white-fleshed guavas had higher levels of TSS, total sugars, reducing sugars. titratable acidity, phenolic compounds and ascorbic acid content then the pink-fleshed fruits.     

Sensory properties of Cheddar cheese: changes during maturation

The aroma, flavour and texture of 16 samples of commercial Cheddar cheese have been profiled after ripening at 10 °C for 3, 4, 6, 8, 10 and 12 months. Systematic changes in sensory character have been studied and the main changes during maturation identified. Although sensory character changed slowly during ripening, assessment early in the maturation period was an unreliable estimate of ultimate sensory character. Progressive changes in Cheddar aroma and flavour, creamy flavour, acid flavour and mouth-coating character were noted during ripening. Changes in minor components of aroma and flavour were also observed but, on average, were small. Two samples eventually developed marked rancid character and another became excessively bitter. The relation between gross composition of the cheese and sensory properties was investigated. In the early stages of ripening, the ratings for Cheddar flavour and mouth-coating character were associated with the salt content of the cheese and with the concentration of fat in dry matter. However, as the cheese matured these associations weakened.     

Instron texture profile of buffalo milk cheddar cheese as influenced by composition and ripening changes

Buffalo milk Cheddar cheese samples of different ages were analysed for compositional attributes (CA), ripening indices (RI) and Instron Textural Profile (ITP). All samples were compositionally alike, except for pH and salt-in-moisture (SM) contents. RI showed significant variations. CA and RI showed highly significant correlations within themselves and with each other, except for moisture with pH, SM with moisture, MNFS, Fat and FDM and Fat with MNFS. The ITPs of cheeses showed significant variations and had highly significant intercorrelations indicating their interdependence. CA (except moisture and MNFS) and RI showed a highly significant correlationship with ITPs. Moisture content showed a highly significant correlationship with all ITPs, except cohesiveness and springiness, where it was significant. MNFS content showed significant correlations only with hardness and brittleness. Stepwise regression analysis revealed that MI was the most predominant factor influencing cheese texture, followed by pH, SM, FDM and TVFA. Knowing Ca and RI, the textural properties of cheeses can be forecast through mathematical equations. Similarly the age of cheese can also be predicted if RI and/or textural properties are known.     

Chemical, physical, and sensorial characteristics of "Terrincho" ewe cheese: changes during ripening and intravarietal comparison

The objectives of this study were to monitor the changes in chemical [moisture, acidity, pH, and water activity (a(w))] and physical (color and texture) parameters of "Terrincho" ewe cheese during 60 d of ripening, and to determine the correlations between the changes in instrumental texture and color parameters and the ripening time of the product. Intravarietal comparison of Terrincho ewe cheese from 5 different dairy plants was performed by evaluation of mechanical parameters from texture profile analysis (TPA) and color parameters in terms of CIELAB color space (L*, a*, and b*). In addition to mechanical and color tests, composition analyses and sensory tests were performed. The results were evaluated with statistical methods (single valued and multivariate analysis). During the first 20 d of ripening, an increase in hardness, fracturability, gumminess, chewiness, and yellowness occurred. Simultaneously, adhesiveness, resilience, L* (inside cheese, "i" and external "e"), and cohesiveness decreased. After 20 d of ripening hardness, fracturability, gumminess, and chewiness decreased and cohesiveness increased. The ripening time of Terrincho cheeses can be estimated with 6 variables: L* (external, e), L* (i), b* (inside cheese, i), hardness, a* (i), chewiness, and a constant. The estimation error was 4.2 d. Evaluation of composition, pH, texture profile analyses, color, and related sensory characteristics of Terrincho cheeses from 5 different dairy plants (with 30 d of ripening) revealed correlations between these parameters.     

Effect of ripening on the mechanical properties of Portuguese and Spanish varieties of olive (Olea europaea L)

The mechanical properties of the table olive, Hojiblanca and Douro varieties from Spain and Portugal respectively, were determined. The results showed that in a tensile test the skin was stronger and stiffer than the flesh. This was also reflected by the strain at failure of the two tissues, the skin being less deformable than the flesh. During ripening, the strength of both skin and flesh of Hojiblanca decreased, whereas the skin and flesh of Douro increased and decreased in strength respectively. In general, Hojiblanca tissues were stronger than Douro tissues. A softening phenomenon was detected during ripening in the flesh of both varieties. The stiffness of the skin of Hojiblanca decreased significantly during ripening, whereas that of the skin of Douro increased but to a lesser extent. However, in general, the skin and flesh of Hojiblanca were stiffer than those of Douro. A cutting test enabled the determination of skin and flesh toughness. However, it is suggested that the flesh contributed to the measurement of skin toughness in the early stages of ripening, as reported for other commodities. The flesh of Hojiblanca was tougher than that of Douro, with both decreasing in toughness during ripening. © 2001 Society of Chemical Industry     

Biochemical changes in new plantain and cooking banana hybrids at various stages of ripening

BACKGROUND: New varieties of plantain and cooking banana with higher yields and improved pest and disease resistance are continuously being bred. There is therefore the need to study their properties during postharvest ripening. This work investigates the effects of ripening on the dry matter content, pH, titratable acidity, ascorbic acid content, browning potential, starch content and reducing and non‐reducing sugar contents of new FHIA 19 and FHIA 20 plantain and FHIA 03 cooking banana hybrids. RESULTS: The starch and ascorbic acid contents of all hybrids decreased as ripening progressed. The starch and dry matter contents of the FHIA 03 cooking banana were reduced from about 750 to < 100 g kg^?1 and from 260 to 190 g kg^?1 respectively after stage 9 of ripening, when samples had more black than yellow colour. The FHIA 03 cooking banana had the highest content of non‐reducing sugars. The titratable acidity of the FHIA 03 cooking banana was higher than that of the FHIA 19 and FHIA 20 plantains. The browning potential of all hybrids decreased after stage 7 of ripening, when samples were yellow with black spots. The FHIA 19 plantain had the lowest browning potential. CONCLUSION: Significant reductions in the dry matter, ascorbic acid and starch contents of the plantain and cooking banana hybrids were observed during the progress of ripening. The cooking banana variety contained lower levels of dry matter, ascorbic acid and starch than the plantain varieties. Copyright © 2008 Society of Chemical Industry     

Biochemical changes during the natural fermentation of the african oil bean (Pentaclethra macrophylla) for the production of Ugba

Changes in the activities of major enzymes and in the proportion of the principal chemical components during the nataral fermentation of ugba from African oil bean (Pentaclethra macrophylla Bentham) were studied. The activities of the enzymes were related to changes in chemical composition. α-Amylase, proteolytic and lipolytic enzyme activity remained detectable throughout the 72-h fermentation period, and reached a maximum at 24-36 h. The levels of amino nitrogen, ammonia nitrogen, reducing sugar, titratable acidity and pH increased with time. A seven-fold increase in the amino nitrogen level occurred during the fermentation. The temperature of the fermentation and the moisture level reached maximum values at 24 h and 48 h of fermentation respectively. These results could provide useful indices for the improved evaluation of ugba fermentation.     

Enzyme activity and biochemical changes of three date palm cultivars with different softening pattern during ripening

The physicochemical composition changes during palm ripening were studied. The activities of invertase and cell wall-modifying enzymes, namely pectin methylesterase (PME), β-galactosidase (β-Gal), endo-1,4-β-d-glucanase (EGase), and cellulase were monitored during growth and ripening of Shahani, Piarom and Deiry cultivars with different textures. Also, we estimated the concentrations of six organic acids by HPLC. Reducing sugars, most of organic acid, pH and TSS increased up to the full-ripe stage of all date types. On the contrary, moisture, macro and microelements and proteins decreased during the same period. Despite a considerable rise in invertase activity (200 units) during ripening of Shahani, no significant trend could be discerned in Deiry cultivar (8 units) at different stages. Our results also showed that cell wall enzymes were increased in activity during ripening and these increases were coincident with fruit softening. Furthermore, our results showed that the composition and the variation of the chemical compositions mainly depended on the cultivar and maturity stage.     

Effect of NaCl on textural changes and protein and lipid degradation during the ripening stage of sufu,a Chinese fermented soybean food

Sufu is made by solid state fungal fermentation (using Actinomucor elegans) of tofu, followed by salting and maturation in dressing mixtures containing salt, alcohol and various other ingredients. NaCl in dressing mixtures strongly affected the changes in textural properties and the hydrolysis of protein and lipid of sufu. Higher salt contents (14% w/w) resulted in increased hardness (+100%) and elasticity (+18%) and reduced adhesiveness (?30%). Hardness and elasticity could be used to judge the extent of sufu ripening. SDS‐PAGE showed the disappearance of all protein subunits at 80 and 110 g kg^?1 salt content; however, some protein subunits were still detectable at 140 g kg^?1 salt content after 60 days of ripening. Higher ratios of free amino nitrogen to total nitrogen (FAN/TN = 0.4–0.45) and free amino acids to crude protein (FAA/CP = 0.24–0.26) were observed in sufu with lower (80 g kg^?1) salt content. FAN/TN and FAA/CP in white sufu (obtained with dressing mixtures containing only salt and alcohol) were higher than those in red sufu (obtained with dressing mixtures containing angkak or kojic red rice) owing to different dressing mixture compositions. Increases in free fatty acids (FFA) were also observed during ripening. FFA levels in sufu with lower salt content increased rapidly during the first 30–40 days and then increased slowly, probably resulting from the formation of fatty acid esters. Lowering the salt content (80 g kg^?1) can shorten the ripening time to 40 days, which is of benefit to manufacturers. However, sufu will spoil, ie undergo souring, during the ripening stage at salt contents of 50 g kg^?1 or lower. Copyright © 2003 Society of Chemical Industry     

Microstructural changes in fat during the ripening of Iranian ultrafiltered Feta cheese

In this study, fat globules in Iranian ultrafiltered Feta cheese (3 to 60 d) were directly observed during the ripening period by scanning electron microscopy. According to images of ultrafiltered Feta cheese samples obtained by scanning electron microscopy, individual fat globules and aggregates of fat were easily distinguishable on d 3 and had completely disappeared within 20 d of storage. On d 20, only the fingerprints of the fat globules and pools of free fat in the casein matrix remained. After 40 d of ripening, the texture was homogeneous and no fat globules or fat voids were detected. Chemical analysis of cheese samples showed that with an increase in the ripening period, the contents of dry matter and fat decreased significantly, whereas the pH values and salt content did not indicate any significant changes.     

凝乳酶对牦牛乳硬质干酪成熟期间蛋白降解的影响

以新鲜牦牛乳为原料,采用小牛皱胃酶、木瓜蛋白酶和微生物凝乳酶制作硬质干酪,探讨凝乳酶种类对牦牛乳硬质干酪成熟期间蛋白质降解的影响。结果表明:三种凝乳酶牦牛乳硬质干酪成熟过程中,不同凝乳酶牦牛乳硬质干酪在成熟期间蛋白质降解能力存在较大差异,总氮（TN）、p H4.6水溶性氮（p H4.6-SN/TN）、12%的三氯乙酸氮（12%TCA-N/TN）、5%磷钨酸氮（5%PTA-N/TN）含量、游离氨基酸均随成熟时间延长不同程度的增加,蛋白氮和酪蛋白氮逐渐降低,多肽氮呈先升高后下降趋势,且微生物凝乳酶降解牦牛乳硬质干酪蛋白能力显著（p<0.05）高于木瓜蛋白酶和小牛皱胃酶。      

Physico-chemical characteristics and sensory quality of two date varieties under commercial and industrial storage conditions

The physicochemical characteristics of two date palm varieties, “Khalas” and “Barhee”, commonly grown in the United Arab Emirates, were studied under commercial and industrial storage conditions. Storage conditions chosen were 2 months and 1 year at −3 °C and at room temperature (∼25 °C). Stored samples were analyzed for sugar, moisture, protein, ash and mineral element contents. Physical measurements on the date fruit, pit and flesh, measurements of the fruit's pitting pressure, shear pressure and modulus of elasticity, as well as sensory evaluation, were carried out on freshly harvested and stored samples. Significant variations in measured attributes were observed with storage treatments, but the two varieties did not behave similarly under matching storage conditions. Quality was best maintained after storage of 2 months at −3 °C for Khalas, and 1 year at −3 °C for Barhee. Overall, storage time and temperature as independent factors alone did not account for all of the observed variation in the studied attributes of Khalas and Barhee. Principal component analysis revealed that most of the variation of the stored dates comes from “size”, followed by “texture” variables. The work pointed to some probable chemical and physiological systems responsible for deterioration of dates, the understanding of which can prove extremely helpful in developing methods of short- and long-term preservation of the fruit.     

The effect of two types of mould inoculants on the microbiological composition,physicochemical properties and protein hydrolysis in two Gorgonzola‐type cheese varieties during ripening

The aim of this paper was to investigate the role of two types of Penicillium roqueforti moulds (type esportazione and dolce) in the ripening of two Gorgonzola‐type cheese varieties. Cheeses were analysed after 4, 14, 30 and 60 days of ripening. Microbiological analysis showed high numbers of total bacterial count, yeasts and moulds in both 60‐day‐old cheese varieties. The concentration of water‐soluble N, nonprotein N and 5% phosphotungstic acid‐soluble N increased significantly during ripening. Patterns of proteolysis by urea‐polyacrylamide gel electrophoresis showed that rind‐to‐core gradients and age‐related changes in moisture and salt content influenced mould and other enzyme activities, which are reflected in various rates of protein degradation. The hydrolysis of αs₁‐ and β‐caseins was more extensive in the core than under the rind of both cheese varieties.     

Fruit ripening phenomena--an overview

Fruits constitute a commercially important and nutritionally indispensable food commodity. Being a part of a balanced diet, fruits play a vital role in human nutrition by supplying the necessary growth regulating factors essential for maintaining normal health. Fruits are widely distributed in nature. One of the limiting factors that influence their economic value is the relatively short ripening period and reduced post-harvest life. Fruit ripening is a highly coordinated, genetically programmed, and an irreversible phenomenon involving a series of physiological, biochemical, and organoleptic changes, that finally leads to the development of a soft edible ripe fruit with desirable quality attributes. Excessive textural softening during ripening leads to adverse effects/spoilage upon storage. Carbohydrates play a major role in the ripening process, by way of depolymerization leading to decreased molecular size with concomitant increase in the levels of ripening inducing specific enzymes, whose target differ from fruit to fruit. The major classes of cell wall polysaccharides that undergo modifications during ripening are starch, pectins, cellulose, and hemicelluloses. Pectins are the common and major components of primary cell wall and middle lamella, contributing to the texture and quality of fruits. Their degradation during ripening seems to be responsible for tissue softening of a number of fruits. Structurally pectins are a diverse group of heteropolysaccharides containing partially methylated D-galacturonic acid residues with side chain appendages of several neutral polysaccharides. The degree of polymerization/esterification and the proportion of neutral sugar residues/side chains are the principal factors contributing to their (micro-) heterogeneity. Pectin degrading enzymes such as polygalacturonase, pectin methyl esterase, lyase, and rhamnogalacturonase are the most implicated in fruit-tissue softening. Recent advances in molecular biology have provided a better understanding of the biochemistry of fruit ripening as well as providing a hand for genetic manipulation of the entire ripening process. It is desirable that significant breakthroughs in such related areas will come forth in the near future, leading to considerable societal benefits.     

黑豆豆乳添加量对Mozzarella奶酪成熟过程中品质的影响

在牛乳中添加不同的黑豆豆乳,研究不同的黑豆豆乳添加量对Mozzarella奶酪在成熟0 d、30 d、60 d、90 d时的水分活度、pH、质构、色泽、蛋白质降解等品质指标变化的影响。结果显示,随着黑豆豆乳添加量在2%～6%范围内的增大,奶酪的水分活度不断增大,pH不断降低,奶酪的硬度、弹性、粘附性、咀嚼性增加,奶酪的明亮度（L*值）下降,红度（a*值）和黄度（b*值）增加,而加入黑豆豆乳的奶酪在成熟过程中蛋白质降解与对照奶酪相似。综合各个指标,在牛乳中加入4%黑豆豆乳条件下制作的黑豆豆乳牛乳奶酪,既有独特的风味,同时奶酪具有较好的色度、质构、蛋白降解等指标特性。     

快速成熟契达干酪成熟期间的理化特性变化

对天然契达(Cheddar)干酪快速成熟期间理化特性进行了研究,结果表明,在21 d内,pH值呈下降趋势(P<0.05),在21 d到35 d的成熟中,pH值缓慢增加(P>0.05);Cheddar干酪快速成熟过程中由于蛋白酶和脂肪酶的作用使蛋白发生水解,pH值为4.6醋酸溶液—水溶性氮质量分数、质量分数为12%的三氯乙酸—可溶性氮和游离氨基酸(FAA)的质量分数都呈明显增加趋势(P<0.05);成熟过程中TPA各项指标均有不同程度的变化,硬度和凝聚性呈先下降后增加的趋势,弹性和咀嚼性呈先上升后下降的趋势。