Changes of composition and free fatty acid contents of Urfa cheeses (a white-brined Turkish cheese) during ripening: Effects of heat treatments and starter cultures

The influences of heat treatments (at 65 °C for 20 min or 72 °C for 5 min) applied to the milk and addition of mesophilic or thermophilic starter cultures, prior to cheese-making, on the composition and free fatty acid contents of Urfa cheeses were evaluated throughout the ripening period. Sensory evaluation of cheese samples was also performed on 90th day. The basic composition of ripened cheese samples was not significantly affected by the heat treatments and starter cultures. Heat treatments adversely affected the lipolysis and sensory properties of Urfa cheeses, particularly at 72 °C. The FFA contents of cheeses made from mesophilic and thermophilic cultures were similar. Cheese made from raw milk had a higher level of lipolysis than the cheeses made from milk inoculated with mesophilic or thermophilic lactic starters (p < 0.05).     

Lipolysis in Urfa cheese produced from raw and pasteurized goats’ and cows’ milk with mesophilic or thermophilic cultures during ripening

Lipolysis was evaluated in Urfa cheese made from raw and pasteurized goats’ and cows’ milk with mesophilic or thermophilic cultures. The acid degree values (ADVs) of the cows’ milk cheeses were significantly (P < 0.05) higher until 60 d of storage than that of cheese made from goats’ milk. Total free fatty acid (FFA) contents of goats’ milk cheese were significantly (P < 0.001) lower than that of cows’ milk cheese throughout ripening, whereas goats’ milk cheese flavour was higher (P < 0.05) than cows’ milk cheese. Pasteurization of milk prior to cheese-making has a negative influence, not only on the level of lipolysis throughout ripening, but also on the relative amounts of short chain FFAs and sensory properties of the cheeses (P < 0.001). Cheese produced without starter bacteria underwent significantly (P < 0.05) higher lipolysis than cheeses produced with mesophilic or thermophilic starter bacteria, while cheese made with thermophilic starter culture had similar flavour to cheese made without starter culture.     

Some properties of urfa cheese (a traditional white-brined Turkish cheese) produced from bovine and ovine milks

In this study, the basic composition and ripening profile of traditional urfa cheese made from ovine and bovine milks were investigated. While cheese made from ovine milk had higher total solids, fat-in-dry matter and total nitrogen, the titratable acidity, salt-in-dry matter, pH, total mesophilic colony count and total yeasts and moulds counts were found to be close to each other. During storage, whilst the total solids content of cheese produced from ovine milk gradually decreased, the variation in the total solids content of cheese made from bovine milk was found to be insignificant. The salt penetration into the cheeses was rapid during the first two weeks of ripening, and it continued to diffuse into the samples throughout storage. Proteolysis developed faster in the cheese made from ovine milk than in cheese of bovine milk. The former sample had higher water soluble nitrogen, nonprotein nitrogen, phosphotungustic acid soluble nitrogen, Proteose-peptone nitrogen and tyrosine levels throughout storage, and the ripening index was higher as well.     

Flavouring of imitation cheese with enzyme-modified cheeses (EMCs): Sensory impact and measurement of aroma active short chain fatty acids (SCFAs)

Enzyme-modified cheeses (EMCs) are used to impart flavour to imitation cheese products. Cheeses (pH 6 or 5.5) were formulated with 5% w/w EMC, having low, medium or high levels of lipolysis and were examined by a sensory panel. Free fatty acid analyses were performed using SPME/GC. The flavour profile of the flavoured cheeses was affected by EMC composition and pH of the cheese base. Cheeses at a pH of 6.0, flavoured with low lipolysis EMCs, were described as ‘bland’. Lowering the pH of the cheese matrix to 5.5 appeared to increase the flavour intensity of the cheese flavoured with low lipolysis EMC and panellists ranked this cheese the highest, describing its flavour as ‘well-balanced and ‘cheesy’. This study shows that the flavours of imitation cheeses are influenced by the level of lipolysis of the EMCs used to flavour them and also by the pH of the cheese base.     

翘嘴红鲌肉腌制工艺优化

目的研究腌制方式和湿腌温度、时间对翘嘴红鲌肉品质的影响。方法以挥发性盐基氮(volatile salt-based nitrogen,VBN)、菌落总数(aerobic plate count,APC)、过氧化值(peroxide value,POV)及感官评分为指标,比较干腌与湿腌法对翘嘴红鲌鱼肉制品品质的影响,在此基础上以腌鱼肉盐分含量、感官评分及盐卤中氨基酸态氮及可溶性蛋白含量为指标,确定最适湿腌条件。结果冷藏后期干腌组鱼肉VBN、APC显著高于湿腌组鱼肉,而感官评分低于湿腌组鱼肉,湿腌组比干腌组鱼肉保质期延长2~3 d;同一腌制温度下,湿腌组鱼肉含盐量、盐卤中氨基酸态氮和可溶性蛋白的含量均随腌制时间延长而增加,最佳腌制工艺为:10~15℃湿法腌制20 min,腌制后鱼肉营养损失相对较少,鱼肉盐分含量约为4.09%。结论相比于干腌法,湿法腌制翘嘴红鲌肉更有利于腌鱼肉的保藏;合适的湿腌温度和时间分别为10~15℃和20 min,此时腌鱼肉具有较好的感官品质,冷藏条件下保质期能达到18 d左右。     

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.     

Comparison of the volatile profiles of Arzúa-Ulloa and Tetilla cheeses manufactured from raw and pasteurized milk

Levels of volatile compounds in Arzúa-Ulloa and Tetilla cheeses manufactured from raw and pasteurized milk were investigated. Analysis of volatile compounds in six raw milk (RM) starter-free cheeses (15–45 days old) and six pasteurized milk (PM) cheeses made with deliberately added starters (15–45 days old) manufactured in different dairies, was performed on an automatic dynamic headspace apparatus coupled to a GC/MS. The volatile fraction of RM cheeses displayed 46 volatile compounds (34 for PM cheeses) including fatty acids, esters, aldehydes, alcohols, ketones, hydrocarbons and sulphur compounds. Fatty acids and several esters were only detected in RM cheeses. Moreover, the highest contents of methylketones, secondary alcohols and branched-chain aldehydes and alcohols were also observed in RM cheeses. All results confirm more intense lipolysis in RM cheeses than in PM cheeses. In addition, branched-chain aldehydes and alcohols were significantly more abundant in RM than in PM cheeses, which indicates that catabolism of branched-chain amino acids was significantly higher in RM cheeses. This study has provided useful information which will allow the selection of starter and non-starter bacteria more suitable for manufacturing Arzúa-Ulloa and Tetilla pasteurized milk cheeses with organoleptic characteristics similar to those of traditional raw milk cheeses.     

The effect of different salting procedures and qualities of raw material on some nutrients during processing and storage of salted-dried mackerel

Salted-dried mackerel ( Scomber scombrus ) was prepared using fresh fish or fish which had been stored in ice for 75h and four methods of salting, namely 15% brine, saturated brine, pickle and dry salting. Samples were analysed for available lysine, thiamine and riboflavin before salting, after salting, after drying and after 1 month's storage at 20°C. Final losses of each of these nutrients were lowest when the fish were pickle cured. Losses were also lower when fresher raw material was used. the use of good quality fish and a pickle salting method is therefore recommended for this type of product.     

Modeling of proteolysis and lipolysis in Iranian white brine cheese

The simultaneous effects of processing variables such as ripening time (20–60 days), ripening temperature (6–10 °C), level of rennet added (1–2 g/100 kg milk) and brine concentration (8–14%, w/v) on the proteolysis, lipolysis and sensory score of Iranian white brined cheese (Feta type) were explored by the means of response surface methodology. The most important effect in proteolytical terms was produced by ripening temperature and ripening time in linear form, but level of rennet added and brine concentration were also significant at the 5% level. In terms of lipolysis, ripening time was dominant factor in both linear and quadratic forms; quadratic effect of ripening temperature was greater than its linear effect.     

Microstructural properties of fat during the accelerated ripening of ultrafiltered-Feta cheese

A commercial pregastric lipase was used to accelerate lipolysis of Iranian ultrafiltered-Feta (UF-Feta) cheese. Scanning electron microscopy images showed that with an increase in lipase levels from 2.0 to 6.0 g 100 kg⁻¹ of retentate, disruption of fat globules increased significantly. On day 3 of ripening and enzyme level of 2.0 g 100 kg⁻¹ of retentate, individual fat globules and fat aggregates were clearly observed on the cheese samples. An increase in the lipase level or ripening period resulted in an increase in the rate of disappearance of fat globules. After 20 days of ripening, no apparent fat globules were observed and fewer fingerprints and voids of free fat were detected, compared to when no enzyme was used.     

盐水法和包灰法腌制咸蛋理化性质的比较

研究了盐水法和包灰法在腌制咸蛋过程中理化品质的变化。结果表明:盐水法腌制的咸蛋黄的DHA含量是包灰法腌制的2倍多,而硬脂酸含量只有包灰法的2/3,其他脂肪酸没有明显差异。两种腌制方法的蛋黄和蛋清蛋白质种类没有差异,咸蛋清主要是相对分子质量为45 000的卵清蛋白,咸蛋黄的相对分子质量为46 000、66 000高密度脂蛋白的载脂蛋白和相对分子质量为100 000的低密度脂蛋白的载脂蛋白。包灰法蛋黄硬化率较高,且盐水法浸油率不如包灰法。包灰法腌制后蛋壳孔比盐水法多且表面粗糙,壳膜纤维直径由于脱水也比盐水法的纤细。两种方法腌制后可以明显看到蛋黄脂蛋白中油脂和载脂蛋白分离,包灰法油脂脱离的更多,蛋白质颗粒直径都在0.2~2μm范围。