Free fatty acids and oxidative changes of a Spanish soft cheese (PDO 'Torta del Casar') during ripening

Free fatty acids (FFA) and lipid and protein oxidation changes during ripening were studied in Torta del Casar cheese. This cheese with protected designation of origin (PDO) is made from raw ewe milk and uses vegetable rennet. Cheeses were analysed at four different stages of ripening at 1, 30, 60 and 90 days. Most FFA significantly increased throughout maturation, except valeric and margaric acids. Acetic acid content increased during ripening and was the most abundant FFA in Torta del Casar cheese at the end of ripening. Short chain fatty acids (SCFA) showed an important increase throughout maturation, especially butyric, isovaleric and isobutyric acids. Lipid oxidation values significantly increased during the first month and decreased in the last 2 months of maturation; however, protein oxidation did not significantly change during ripening. Changes in FFA, especially SCFA, could have great importance in Torta del Casar cheese final characteristics; however, oxidative reactions did not play an important role.     

低钠盐对不同成熟条件下自然发酵牦牛肉灌肠脂质氧化及挥发性风味物质的影响

探究降低钠盐含量对自然发酵牦牛肉灌肠脂质氧化及风味品质的影响。分别添加2%（低钠盐）和4%（对照）钠盐制备灌肠,并分别以自然成熟和恒温成熟两种方式制备成品,测定成熟过程中相关理化指标。结果表明,两种成熟方式中低钠盐组的水分含量、1,1-二苯基-2-三硝基苯肼自由基清除能力和羟自由基清除能力均显著低于对照组（P＜0.05）,而pH值显著高于对照组（P＜0.05）。4 种处理组灌肠脂质水解和脂质氧化程度随时间延长升高,成熟过程中两种成熟方式中低钠盐组的脂质水解、氧化程度均显著高于对照组（P＜0.05）;自然成熟的两组灌肠脂氧合酶活力无显著差异（P＞0.05）,而后期恒温成熟灌肠低钠盐组脂氧合酶活性显著高于对照组（P＜0.05）。此外,从灌肠中共检出69 种挥发性风味物质,3 个主成分累计贡献率达96.206%。主成分分析结果表明,第9天和第17天成熟结束,低钠盐组中由脂质氧化生成的醇、醛等物质的相对含量较对照组多。不同钠盐含量对灌肠的脂质水解、氧化有显著影响,直接减少钠盐质量分数至2%,可能会促进脂质的氧化。     

Increase on free fatty acids during ripening of anchovies (Engraulis anchoíta)

The changes of free fatty acids (FFA) during the ripening of salted anchovy was studied. In the course of the curing process, the content of free fatty acids (FFA) in the muscle increased fifteen-fold, mostly in the first 100 days of the process. Each sample was subjected to sensory evaluations. A high correlation between FFA contents and sensory scores was found. Therefore the determination of FFA is proposed as an objective index to assess the ripening of salted anchovies.     

冻融循环对熟制鲣鱼暗色肉脂质变化的影响

为探究冻融循环对熟制鲣鱼暗色肉脂质变化的影响,对熟制鲣鱼暗色肉进行冻融循环（0、2、4、6、8 次）贮藏,测定冻融过程中样品的过氧化值（peroxide value,POV）、酸价（acid value,AV）、pH值、脂质组成、脂肪酸组成等指标。结果显示,在冻融循环贮藏过程中,脂质组成发生明显变化,甘油三酯（triacylglycerol,TAG）和磷脂（polar lipid,PL）质量分数明显降低,游离脂肪酸（free fatty acid,FFA）质量分数明显升高。在冻融循环过程中暗色肉的pH值显著减小,POV和AV显著增加（P＜0.05）。脂质中总饱和脂肪酸和总多不饱和脂肪酸含量都逐渐下降,TAG和PL中脂肪酸含量明显下降,其中PL中总多不饱和脂肪酸含量下降明显,FFA中总多不饱和脂肪酸含量显著升高（P＜0.05）。主成分分析（principal component analysis,PCA）和偏最小二乘判别分析（partial least squares discriminant analysis,PLS-DA）结果表明,经过不同冻融次数的鱼肉之间存在一定的差异性,且随着冻融次数的增加脂质氧化程度不断加剧。相关性分析结果表明FFA质量分数与POV、AV呈正相关,与PL质量分数、TAG质量分数、pH值呈负相关。实验结果表明冻融循环会影响熟制鲣鱼暗色肉脂质组成,同时引起脂质的氧化分解。这为熟制鲣鱼暗色肉在运输和贮藏过程中脂质控制提供一定的理论指导。     

Free fatty acids and oxidative changes of a raw goat milk cheese through maturation

Free fatty acids (FFA) and lipid and protein oxidation changes were studied throughout maturation process of a raw goat milk cheese with protected designation of origin. Cheeses were analyzed at 4 different times of maturation, at 1, 30, 60, and 90 d. All FFA significantly increased during maturation and the relative increase was higher for long-chain than medium- or short-chain FFA. At the end of maturation, oleic (C18:1 n9), butyric (C4:0), and palmitic (C16:0) acids were the most abundant. The higher levels of short-chain fatty acids (SCFA) regarding total FFA obtained at the end of Ibores cheese ripening compared with other raw goat milk cheeses, highlight the notable role of SCFA on the flavor of this cheese owing to their low-odor thresholds. Lipid oxidation values significantly increased during maturation process but low levels of malondialdehyde were reported; however, protein oxidation did not significantly change during ripening.     

The reuse of brine to enhance the ripening of marine and freshwater fish resistant to marinating

Cold marinades are produced mainly from the Clupeidae fish, because meat of other fish species does not reach a desired level of ripeness in the acid-salt environment of fresh brine. Hence, this work presents an innovative idea of reusing brine including cathepsins and peptides for marinating cod, salmon, trout, and carp. The extent of marinades ripening improvement depended on fish resistance to the marinating process. The reused brine proved best in improving the ripening of fatty fish (salmon and trout), which were qualified to the first class of resistance to marinating. In the case of cod, the reuse of brine did not elicit a satisfactory improvement in meat ripening. Therefore cod was qualified to the second class of resistance. The reuse of brine resulted in decreased values of lipid oxidation indices (except for cod) and meat hardness, and in increased scores for overall sensory evaluation and total volatile bases nitrogen value.     

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     

LIPOLYTIC AND OXIDATIVE CHANGES OF BARLEY LIPIDS DURING MALTING AND MASHING

Lipolytic and oxidative changes of barley lipids were studied during malting and mashing. The amount of lipid decreased by 23% during malting and changes in the composition of lipid classes were minor. On the other hand, during mashing the amount of free fatty acids (FFA) increased which indicated, that lipid hydrolysis had occurred. The same phenomenon was seen when malt flour was soaked in water at 23°C. The triglyceride (TG) and polar lipid (PL) contents were reduced and the proportion of FFA in total lipids was increased. Following similar soaking of barley flour, TG and PL were reduced but the accumulation of FFA and especially linoleic acid (LA) was slight. The results were consistent with the data on lipoxygenase activity (LOX) during malting. During steeping LOX decreased and was 15–20% of the activity of raw barley at the beginning of germination. The activity remained low during germination but rose sharply in the middle of kilning only to decrease again to a very low level at the end of kilning (5%). This in combination with the fact that the proportion of FFA remained high in the soaked malt samples suggests that the oxidation by LOX is negligible in the malt samples. However, the data suggest that mashing of barley, but not that of malt, includes the potential for the formation of highly polar lipid oxidation products.     

Biogenic amines in Iranian white brine cheese: modelling and optimisation of processing factors

The simultaneous effects of processing factors such as ripening time (25–75 days), ripening temperature (4–14 °C) and brine concentration (10–13%) on biogenic amines content, proteolysis and sensory score of Iranian white brine cheese were studied, in 12 cheeses. Response surface methodology (RSM) was used to minimise biogenic amines content. At low level of ripening time, biogenic amines content decreased with increasing levels of brine concentration but at high level of ripening time, brine concentration had inverse effect. Ripening time showed quadratic effect on biogenic amines content. Based on biogenic amines content and sensory score, the optimum conditions were 13% brine and ripening at 9–14 °C for 43–65 days.     

萨拉米香肠发酵成熟过程中蛋白质水解及脂质氧化规律

研究萨拉米香肠从加工到发酵阶段的蛋白质及脂质水解氧化规律。结果显示,在萨拉米香肠发酵成熟过程中,蛋白质水解指数不断增加,并且在高温发酵初始及发酵15 d阶段是蛋白质水解和游离氨基酸总量累计的主要阶段。发酵45 d,游离氨基酸总量略降低但与发酵中期总量差异不显著。另外,中性脂质及游离脂肪酸相对含量显著增加（P＜0.05）,而磷脂相对含量不断降低;除油酸和鳕油酸外的不饱和脂肪酸含量在发酵成熟过程中均呈现先升高后降低的趋势,并且该趋势与脂质氧化的变化趋势相同。因此,萨拉米香肠发酵成熟过程中脂质水解及氧化的发生是同步的。     

Effect of fat content on aroma generation during processing of dry fermented sausages

Dry fermented sausages with different fat contents were produced (10%, 20% and 30%). The effect of fat content and ripening time on sensory characteristics, lipolysis, lipid oxidation and volatile compounds generation was studied. Also, the key aroma components were identified using gas chromatography (GC) and olfactometry. High fat sausages showed the highest lipolysis and lipid oxidation, determined by free fatty acid content and thiobarbituric acid reactive substances (TBARS), respectively. A total of 95 volatile compounds were identified using SPME, GC and mass spectrometry (MS). Fat reduction decreased the generation of lipid derived volatile compounds during processing while those generated from bacterial metabolism increased, although only at the first stages of processing. The consumers preference in aroma and overall quality of high and medium fat sausages was related to the aroma compounds hexanal, 2-nonenal, 2,4-nonadienal, ethyl butanoate and 1-octen-3-ol which contributed green, medicinal, tallowy, fruity and mushroom notes.     

EFFECT OF IMMATURE AND OFF-COLORED SEEDS ON THE LIPID QUALITY OF MILLED FLAXSEED

The effect of visibly inferior flaxseed ( Linum usitatissimum L.) on the lipid quality of milled flaxseed was investigated. Flaxseed was aspirated and separated into low-, medium- and high-density fractions. All density fractions contained ≤ 0.1% broken seed, ≤ 0.4% contrasting seed and ≤ 0.25% extraneous material. The low-density fraction contained the most immature (2.8%) and off-colored seed (4.1%). Immature seed had a lipid content of 40.8%, a peroxide value (PV) of 2.69 meq/kg and a free fatty acid (FFA) content of 1.06%. The off-colored seed had a lipid content of 38.1%, a PV of 5.79 meq/kg, and a FFA content of 1.89%. Hand-cleaned seed (averaged across fraction density) had a lipid content of 41.4%, a PV of 0.41 meq/kg and FFA content of 0.37%. The removal of seed defects improved flaxseed quality and improved lipid quality in the low-density fraction.

PRACTICAL APPLICATIONS

Lipid oxidation is a major concern when using milled flaxseed as a food ingredient. These results indicate the importance of removing off-colored and immature flaxseed. Seed lots that contain immature and off-colored seed likely will have poor lipid quality and, when milled, be more susceptible to lipid oxidation during storage than will seed lots free of immature and off-colored seed.     

Discoloration and lipid deterioration of farmed giant catfish (Pangasianodon gigas) muscle during refrigerated storage

ABSTRACT:  Discoloration and lipid deterioration of farmed giant catfish ( Pangasianodon gigas) muscle during 14 d refrigerated storage were investigated. Lipid deterioration, lipolysis, and lipid oxidation in both dorsal and ventral muscles increased as storage time increased. A progressive formation of primary lipid oxidation products monitored by the increase in conjugated dienes (CD) was observed ( P < 0.05) and the increase in thiobarbituric reactive substances (TBARS), an index of secondary lipid oxidation products, was noticeable throughout the storage ( P < 0.05). The pH of both dorsal and ventral muscles tended to increase as storage time continued ( P < 0.05). A gradual increase in free fatty acid (FFA) formation was found within the first 10 d of refrigerated storage ( P < 0.05), suggesting hydrolysis induced by lipases and phospholipases. However, a sharp decrease in FFA content was observed at the end of storage. Refrigerated storage also resulted in changes in redness index of both dorsal and ventral muscles. These changes were coincidental with the changes in metmyoglobin content. Therefore, the discoloration and lipid changes in giant catfish muscle during refrigerated storage depended on the muscle type and might be related to the difference in composition between dorsal and ventral muscles.     

Quantification of short-chain free fatty acids in "Terrincho" ewe cheese: intravarietal comparison

Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was employed for the quantification of volatile free fatty acids (FFA) in "Terrincho" ewe cheese. Solid-phase microextraction quantitative analysis was feasible under equilibrium situations as long as the conditions of agitation and the adsorption time were held constant. An excellent linear relationship between the amount of the adsorbed analyte and its initial concentration in the sample matrix was obtained when an adequate amount of sample was chosen. Thus, quantification was possible if biases due to competition or linear range excesses were controlled. Solid-phase microextraction sampling was carried out at 65 degrees C, and a fiber coated with an 85-micro/m polyacrylate film was chosen. After equilibration at 65 degrees C for 40 min, the fiber was exposed to the headspace above the sample for 20 min and then inserted into the gas chromatograph. The evolution of the volatile FFA during Terrincho ewe cheese ripening was analyzed for a 60-d period. An overall increase in FFA contents was verified up to 30 d of ripening. Between 30 and 45 d most FFA did not suffer significant changes. All FFA increased significantly by the 60-d ripening period. The excessive lipolysis observed at 60 d of ripening may result in the presence of off-flavors. Principal component analysis performed for intravarietal comparison of volatile FFA composition of 19 Terrincho cheeses, analyzed at 30 ripening days, enabled discrimination between cheeses produced at five different dairy plants.     

Monitoring the chemical and textural changes during ripening of Iranian White cheese made with different concentrations of starter

The effect of the concentration of starter inoculated to milk on the composition, free tyrosine-tryptophan content, microstructure, opacity, and fracture stress of Iranian White cheese (IWC) was studied during 50 d of ripening in brine. Three treatments of cheese were made using 1-fold (IWC1S), 2-fold (IWC2S), and 4-fold (IWC4S) concentrations of a direct-to-vat mesophilic mixed culture containing Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis as starter. As ripening progressed, moisture and protein contents of the treatments continuously decreased, whereas their total ash, salt, and salt in moisture contents increased. Fat content and pH of cheeses remained stable during ripening. The pH of cheese milk at the time of renneting, which decreased by increasing the concentration of starter (6.57, 6.49, and 6.29 for IWC1S, IWC2S, and IWC4S, respectively), significantly affected most of the chemical characteristics and opacity of cheese. Lower pH values at renneting decreased moisture and ash contents, whereas cheese protein content increased. The concentration of free tyrosine-tryptophan in curd increased at first 29 d but decreased between d 29 and 49 of aging. The changes observed in cheese whiteness followed the changes in moisture content of the treatments. As the concentration of starter inoculated to milk increased, the value of fracture stress at a given ripening time significantly decreased, leading to a less resistant body against applied stress. A similar trend was also observed for fracture strain during cheese ripening. The micrographs taken by scanning electron microscopy provided a meaningful explanation for decrease in the value of fracture stress. As the cheese ripening progressed or the concentration of starter increased, the surface area occupied by the protein fraction in cheese microstructure decreased, leading the way to lower the force-bearing component in cheese texture.     

风干成熟工艺对风鸭脂质分解氧化影响的研究

以樱桃谷鸭为原料,通过对高温风干成熟和低温风干成熟工艺过程中鸭胸肉和皮下脂质TBARs 值、POV值及脂肪氧合酶活力的比较,研究加工过程中脂质分解氧化规律及其与工艺温度、盐分和时间的相关性。结果表明：风干72h 时,高温风干成熟加工过程中皮下脂肪的POV 值比低温风干成熟工艺降低了30.77%,脂肪氧合酶活力提高了7.26%,TBARs 值无显著变化;风干96h 时,鸭胸肉POV 值比低温风干工艺降低了62.50%;高温风干成熟过程中游离脂肪酸(FFA)总量与温度呈正相关,鸭胸肉中盐分和TBARs 值呈显著的正相关(p ＜ 0.05),可以认为盐含量与温度是影响风鸭制作过程中脂质分解氧化的主要因素。     

Effect of ascorbate and ascorbyl palmitate on lipid oxidation in semi-dry saugages manufactured from pork materials differing in stability towards oxidation

Semi-dry fermented sausages were manufactured from three batches of pork slightly differing in their polyenoic fatty acid levels and α-tocopherol contents. The sausage doughs were treated as follows: (1) control, (2) ascorbate, (3) ascorbyl palmitate and (4) a combination of ascorbate and ascorbyl palmitate. After brine fermentation, products ripened at 15°C were evaluated for rancidity by peroxide values and TBA numbers. During ripening important differences in stability towards oxidation were generally not observed. Both peroxide and TBA values gradually increased linearly with time. For the TBA values, gradients for the products derived from the three diet groups differed considerably. Only two of six batches containing increased levels of α-tocopherol and product antioxidants exhibited slightly improved stability towards oxidation, as judged by peroxide and TBA values. Sensory evaluations, performed only on the product series containing ascorbate, failed to reveal any positive effect in favour of the increased α-tocopherol content. Thus, for semi-dry sausages manufactured from pork materials with a slightly increased sensitivity towards oxidation, results indicated with there was little advantage to increasing the levels of α-tocopherol in the meat by dietary means or to changing the current commercial practice of adding ascorbate to the sausage doughs.     

腌制风干过程中卵形鲳鲹鱼肉性质、蛋白质氧化及游离氨基酸的变化

为探究卵形鲳鲹在腌制风干过程中蛋白质氧化及游离氨基酸的变化规律,对卵形鲳鲹鱼肉含水率、盐含量、质构特性、肌原纤维蛋白二级结构、羰基含量、巯基含量、蛋白质水解指数、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳图谱和游离氨基酸等进行测定分析。结果表明：在腌制风干过程中,卵形鲳鲹鱼肉的盐含量整体呈上升趋势,含水率下降,硬度增加,而弹性则先上升后下降。鱼肉蛋白质在加工过程中发生氧化反应,羰基含量明显增加,而巯基含量明显下降,同时肌原纤维蛋白二级结构中α-螺旋含量减少,而无规卷曲含量增加。在加工过程中肌球蛋白重链条带和肌动蛋白发生明显变化,肌球蛋白重链条带变浅并在风干后消失,表明肌原纤维蛋白发生水解;鱼肉的蛋白质水解指数增加,非蛋白氮含量在腌制后下降而在风干过程中增加;游离氨基酸总量在干制1 d后达到最高,鲜味氨基酸和苦味氨基酸含量整体呈上升趋势。本研究可为腌制水产品加工过程中品质控制提供一定理论参考。     

Changes in wheat lipids during mixing and resting of flour-water doughs

Lipids extracted with water-saturated n-butanol from flour and flour-water doughs were examined to determine the extent of oxidations and other changes which occurred in mixing and resting dough. Extracted lipids were converted to fatty acid methyl esters (FAME) and quantified by gas-liquid chromatography (g.l.c.) using heptadecanoic acid (17 : 0) as internal standard. The original flour or dough and the corresponding solvent-extracted residues were acid hydrolysed, and the hydrolysate lipids converted to FAME for g.l.c. determination of the total lipid and residual unextracted lipid contents. The total flour or dough lipids equalled the extracted lipids + unextracted lipids, except where there were unavoidable autoxidative losses of linoleate (18 : 2) and linolenate (18 : 3). The unextracted flour lipids (13% of total lipids) were not oxidised during dough mixing. There were no changes in any of the extracted lipid classes other than free fatty acids (FFA) and monoglycerides (MG) which showed losses of 18 : 2 and 18 : 3 after aerobic dough mixing. Losses of FFA and MG are attributed to lipoxygenase activity during dough mixing and the period immediately after. The small amount of 18 : 2 in the “free” petroleum ether-extracted FFA appeared to be unaffected by lipoxygenase. Recoveries of FFA other than 18 : 2 or 18 : 3 were constant, indicating no lipolysis of glycerolipids and no general oxidation or degradation of FFA. Experiments with [U-¹⁴C]palmitic acid confirmed that there was no oxidation, degradation or re-esterification of FFA. Much of the non-polar lipids (steryl ester, triglyceride, diglyceride, FFA, MG) and almost all of the polar lipids were bound on dough mixing. Binding was non-selective with regard to fatty acid composition. Triglyceride was the only lipid class bound to a greater extent in anaerobic dough than in aerobic dough. Some selectivity of binding between lipid classes was indicated.     

Effect of artisanal kid rennet paste on lipolysis in semi-hard goat cheese

This study examined the use of hygienised kid rennet pastes in model cheese systems and also in goat milk semi-hard cheeses to promote lipolysis. The results obtained indicated that the use of rennet paste caused greater lipolysis and increased, mostly, the short-chain free fatty acid (FFA) content. The model systems made with whole goat’s milk using rennet paste and commercial rennet mixture exhibited a higher FFA content than did the rennet paste-free controls (31,600 vs. 25,600 μmol/kg cheese). For the pilot cheeses made with bovine rennet and rennet paste mixture, the increase in FFA level after 45 days of ripening compared with the cheeses prepared only with commercial rennet was as much as 6600 (μmol/kg cheese) and the increase in the butyric acid content was also 1650 (μmol/kg cheese). Moreover, after 15 days of ripening, industrially prepared cheeses made with rennet paste exhibited greater levels of FFA than did the cheeses made with commercial rennet (11,500 μmol/kg at 45 days of ripening). Their flavour was stronger and the organoleptic characteristics were better accepted, which implies less ripening time for commercial cheese manufacture.