The role of copper in the manufacture of Finnish Emmental cheese

The effects of added copper in the manufacture of Finnish Emmental cheese were studied. Consequently, cheeses were produced with or without the copper supplement and a facultative heterofermentative strain, Lactobacillus rhamnosus Lc705, which is currently utilized as a protective culture in large-scale manufacture in Finland. Cheeses were examined at 1, 7, 30, 60, and 90 d from the microbiological, chemical, and sensory points of view. Organic acid production was affected by the presence of copper in the cheeses. The addition of copper to cheesemilk increased the level of primary proteolysis and slowed secondary proteolysis as measured by nitrogen content in different extracts after citrate fractionation of cheeses, in pH 4.4-soluble nitrogen and 5% phosphotungstic acid-soluble nitrogen, respectively. The presence of copper appears to positively regulate the sensory characteristics of the cheese produced in our conditions; in particular, consistency was affected significantly. The role of the Lb. rhamnosus Lc705 protective strain has not been shown to have important effects on most of the parameters that influence the final quality of the cheeses. Although the traditional plating systems for revealing bacterial populations during cheese manufacture did not reveal any drastic differences caused by the presence of copper, the results from chemical and sensory analyses suggest that its use plays a significant role in the regulation of bacterial physiological and biochemical activities, which in turn affect the sensory quality of Emmental cheese.     

北京市蔬菜硝酸盐和亚硝酸盐污染状况评价

为了解北京市蔬菜中硝酸盐和亚硝酸盐的污染情况 ,于 2 0 0 3年 4月～ 8月从北京 15个菜市场采集应季蔬菜样品 ,共 4 0个品种 4 44份样品 ,用国标法 (GB T 5 0 0 9 33— 2 0 0 3)分析蔬菜中的硝酸盐和亚硝酸盐的含量。结果显示 :检测样品中 ,污染程度严重的占 33 1% ;中、重度污染的占2 3 6 % ;轻度的占 4 3 2 % ;硝酸盐的含量依次为绿叶菜类 >白菜类 >根茎类 >瓜茄类 >葱蒜类 >豆类 >果类 >水生植物类 ,但同一类蔬菜不同品种的硝酸盐的含量差别较大 ,从几倍到几十倍 ;同一品种的蔬菜中硝酸盐含量差别也很大 ,可能与产地、生长条件不同有关。蔬菜中亚硝酸盐含量相对较低 ,其含量与蔬菜的新鲜程度有关。研究结果提示需要制定限量标准 ,加强监督管理     

Prediction of sensory attributes of European Emmental cheese using near-infrared spectroscopy: A feasibility study

The present work evaluated the ability of near infrared (NIR) spectroscopy in predicting some sensory attributes of 20 Emmental cheeses originating from different European regions. For the purpose of this study four appearance and texture attributes, namely, adhesivity, friability, elasticity and firmness and six olfacto-gustatory attributes namely, aroma intensity, odour intensity, bitterness, saltiness, acidity and sweetness were selected by the sensory panel. Calibration models between sensory properties and NIR spectra were developed using partial least squares (PLS) regression. The squared correlation coefficients (R²) were greater than 0.5 for adhesivity, elasticity, firmness, aroma, bitterness, saltiness, acidity and sweetness. In addition, a good correlation between sensory attributes and NIR spectra was found using canonical correlation analysis (CCA). Therefore, this work demonstrates the feasibility of NIR to predict some sensory attributes since a relatively high correlation between sensory data and NIR spectra was found. However, further research with a large data bases will be needed in order to validate the method.     

Influence of manufacturing conditions on thermo‐physical properties of ripened experimental Emmental‐type cheese and comparison with commercial Emmental cheese

Experimental Emmental cheese was produced at pilot plant scale with varied process conditions, and the ripened cheeses were analysed in terms of thermo‐physical properties. The amount of propionic acid and the temperature at tan δ_max ( loss factor) were significantly influenced by varied process parameters. Experimental cheeses were compared to commercial Emmental cheese by the application of principal component analysis. Commercial Emmental cheese was clearly discriminated from experimental Emmental cheese mainly due to the melting behaviour. The results allow the establishment of a small‐scale process for Emmental cheese production to promote product development on a time and cost‐saving level.     

The design of a three strain starter system for Cheddar cheese manufacture exploiting bacteriocin-induced starter lysis

A three strain starter system was developed for increasing the level of starter cell lysis during cheese manufacture and ripening. The composition of this starter combination includes a bacteriocin (lactococcin A, B and M) producer which causes the lysis of a second strain (sensitive to bacteriocin activity) during cheese manufacture, and a third strain resistant to bacteriocin activity. The latter strain plays an essential role in ensuring acid production during cheese manufacture. Cheeses manufactured at pilot-scale (450 L vats), with the three strain starter combination were assessed for levels of the intracellular enzyme, lactate dehydrogenase, released into the cheese matrix during ripening. Experimental cheeses, manufactured with the bacteriocin-producing adjunct, exhibited higher levels of free amino acids and greater release of intracellular LDH than control cheeses manufactured in its absence. Cheese was subject to sensory analysis which revealed that experimental cheese showed a decrease in bitterness over cheeses manufactured without the bacteriocin-producing adjunct. Thus, this three strain system offers manufacturers a reliable starter system exhibiting increased lysis with concomitant improvements in cheese flavour.     

A comparison and joint use of NIR and MIR spectroscopic methods for the determination of some parameters in European Emmental cheese

The determination of winter cheese chemical properties, namely, fat, sodium chloride (NaCl), pH, non protein nitrogen (NPN), total nitrogen (TN) and water soluble nitrogen (WSN) was done using spectroscopic technologies with different wavelength zones. The Emmental cheeses provided from different European countries were studied. A total of 91 cheeses produced during the winter time in Austria (n=4), Finland (n=6), Germany (n=13), France (n=30) and Switzerland (n=38) were analysed by near infrared (NIR) and mid infrared (MIR) spectroscopies. The combination of these two spectral regions (sum of their spectra) was also studied. The partial least square (PLS) regression with the leave one-out cross validation technique was used to build up calibration models using data set designated as calibration set. These models were validated with another data set designated as validation set. The obtained results suggest the use of the NIR for the determination of fat and TN contents, and the MIR for NaCl and NPN contents as well as for the pH. Similar results were obtained for WSN using the two techniques together. The combined spectra of both NIR and MIR did improve the results, while providing comparable results to those obtained from either the NIR or MIR spectroscopy.     

The influence of diet and breed of cow on the efficiency of conversion of milk constituents to curd in cheese manufacture

The influence of diet on the efficiency of conversion of milk solids to cheese in two breeds of cow, viz. Jersey and Friesian, was examined. An increase in the efficiency of conversion of milk solids to cheese in Jersey milks produced from cows on winter diets as compared with a typical summer diet was shown to be associated with an improvement in the level of fat retention in curd. The difference in fat retention could to some extent be related to the overall fat content of the milk, the casein to fat ratio and the distribution in the size of the fat globules but these factors when considered collectively or independently could not adequately explain the differences in fat retention observed in these experiments. The level of fat retention in curd was not influenced by the thermal properties of the mik fat.     

Application of the MIR for the determination of some chemical parameters in European Emmental cheeses produced during summer

This study examines the feasibility of using the mid infrared (MIR) spectroscopy for the determination of some parameters in European Emmental cheeses produced in summer from different geographic origins. A total of 72 Emmental cheeses (4 samples from Finland, 6 samples from Germany, 8 samples from Austria, 27 samples from France and 27 samples from Switzerland) were investigated. Total nitrogen (TN), water soluble nitrogen (WSN), non protein nitrogen (NPN), sodium chloride (NaCl) and pH were analysed by the reference methods. The MIR-transmission of the investigated cheeses was measured by a Nicolet Magna 750 IR spectrophotometer in a measurement range between 4000 and 400 cm⁻¹. The best results for WSN (R ²=0.80; ratio of standard deviation to root mean square error of prediction (RPD) =2.22), NPN (R ²=0.71, RPD=1.85), pH (R ²=0.56, RPD=1.50), NaCl (R ²=0.47; RPD=1.37) and TN (R ²=0.33; RPD=1.11) were obtained when the spectra were subjected to the first derivation and smoothing after being subjected to maximum normalisation. It can be concluded that the MIR-transmission spectroscopy could be considered as an alternative technique for the determination of NPN and WSN of Emmental cheeses originating from different European countries. The NaCl, pH and TN can also be estimated, but with much lower precision.     

Evolution and distribution of phospholipids in cheese and whey during the manufacturing of fresh cheese from cows' milk

In this study, we report on the evolution of phospholipid contents and their distribution in cheese and whey, during the production of fresh cheese. We found that the phospholipid content in the total mass of whey and fresh cheese together was greater than the content of phospholipids in the starting milk used to make them. This increase was probably due to bacterial growth during fermentation and the consequent synthesis of phospholipids to generate cell membranes. In the coagulation process, ≈20% of the phospholipids were drained in the whey. Based on this result, we conclude that whey might be an interesting source of phospholipids, mainly phosphatidylethanolamine and sphingomyelin, for the food industry.     

Development of the milk fat microstructure during the manufacture and ripening of Emmental cheese observed by confocal laser scanning microscopy

Changes in the physico-chemical properties and microstructure of milk fat globules were investigated during the manufacture and ripening of Emmental cheese. The measurement of fat globule size and apparent zeta-potential showed that they were slightly affected during cheese milk preparation, i.e. storage of cheese milk overnight at 4 °C and pasteurisation. After rennet-induced coagulation and heating of curd grains, coalescence caused the formation of large fat globules (i.e.>10 μm). The structure of fat in Emmental cheese was characterised in situ using confocal laser scanning microscopy (CLSM). The rennet-induced coagulation lead to the formation of a continuous network of casein strands in which fat globules of various sizes were entrapped. Heating of curd grains induced the formation of fat globule aggregates. Pressing of the curd grains resulted in the greatest disruption of milk fat globules, their coalescence, the formation of non-globular fat (free fat) and the release of the milk fat globule membrane (MFGM) material. This study showed that milk fat exists in three main forms in ripened Emmental cheese: (i) small fat globules enveloped by the MFGM; (ii) aggregates of partially disrupted fat globules and (iii) free fat, resulting from the disruption of the MFGM and allowing free triacylglycerols to fill voids in the protein matrix. The curd grain junctions formed in Emmental cheese were also characterised using CLSM: they are compact structures, rich in protein and devoid of fat globules.     

晋南野菜和蔬菜硝酸盐、亚硝酸盐和维生素C含量分析

目的对山西南部的10种野菜和4种常食用蔬菜的硝酸盐、亚硝酸盐和维生素C含量进行测定。方法硝酸盐含量测定采用镉柱法;亚硝酸盐含量测定采用盐酸萘基乙二胺法;维生素C含量测定采用2,6-二氯酚靛酚滴定法。结果苜蓿、黄瓜和西红柿的硝酸盐含量低于轻度污染水平,亚硝酸盐含量低于亚硝酸盐含量的限量标准,维生素C的含量较低,属于一级蔬菜,可以安全生食;马齿苋、荠菜、蒲公英的硝酸盐含量低于中度污染水平,亚硝酸盐含量低于或相当于亚硝酸盐含量的限量标准,维生素C的含量高或较高,属于二级蔬菜,不宜生食,可盐渍和熟食;苣荬菜、车前草、苦菜、胡萝卜的硝酸盐含量过高,低于重度污染水平,不宜生食和盐渍,可以熟食;藜菜、菠菜、白蒿、地肤的硝酸盐含量高于1234mg/kg,属于高度污染水平,亚硝酸盐含量超过或相当于亚硝酸盐含量限量标准,维生素C的含量高或极高,不宜食用或限量食用。结论大多数供试野菜的各个指标含量均高于栽培蔬菜。     

The effect of humidity controlled environment on Stilton cheese

The aim of this study was to analyse the effects of different relative humidity levels on the maturation and eventual quality of blue Stilton cheese. Cheese samples from the same vat were subjected to different humidity conditions in order to assess effects on the moisture and weight of the cheeses. Analysis showed that exposure to a higher level of humidity during the maturation period had an effect on the moisture levels of the cheese throughout this stage and also had an effect on the overall weight loss of the cheese. It was concluded that increasing the relative humidity of the maturation environment from 70% to 85% would reduce the variation in moisture and weight of the cheese as well as increasing the yield by reducing the weight lost from moisture evaporation (termed ‘the angels share').     

The nutritional significance of cheese in the UK diet

Cheese currently suffers from an adverse nutritional image largely due to a perceived association between saturated fatty acid, cholesterol and the salt content of cheese with cardiovascular disease. However, cheese is also a rich source of essential nutrients such as proteins, lipids, vitamins and minerals that play an integral part of a healthy diet. This review outlines the composition, structure and physiological characteristics of the nutritionally significant components of cheese, whilst presenting some of the controversies that surround the role of cheese in dietary guidelines and the potential cheese has to improve health in the UK population.     

Simultaneous Determination of Nitrite and Nitrate in Milk Samples by Ion Chromatography Method and Estimation of Dietary Intake

The presence of nitrate and nitrite in foods may be considered hazardous after ingestion in the gastrointestinal tract due to their reaction with naturally occurred secondary amines to form potentially carcinogenic nitrosamines. Due to this fact, a new method was developed in this study for the simultaneous determination of nitrite and nitrate in milk samples using by ion chromatography. Proposed mobile phase composed of sodium hydrogen carbonate and sodium carbonate (1.0 and 3.2 mmol/L) with a flow rate of 0.7 ml/min. The average recoveries for nitrate and nitrite were higher than 86 and 88%, respectively. The limit of detection for nitrate and nitrite were 0.24 and 0.09 mg/L, respectively. The results of 102 real milk samples showed nitrate was found in all of the samples (100%) with a mean of 34 ± 11 mg/L, while nitrite was found in none of the samples. The mean intake of nitrate in all age groups was lower than World Health Organization guideline. The present assessment concludes that the maximum contaminant level was equal to 82.8 mg/L nitrate. This method was fast, sensitive and accurate and is capable of being an alternative method in food control laboratories for investigation of nitrite and nitrate content. This is the first study of the determination and survey of nitrite and nitrate and exposure assessment of the Iranian population to nitrite and nitrate level in milk, which was widely used in infants and adolescents as one of the basic food components.     

The effects of carbon dioxide addition to cheese milk on the microbiological properties of Turkish White brined cheese

This study invest0igated the effect of CO₂ added to achieve three pH levels: pH 6.1, pH 6.2 and pH 6.3 for treatments X, Y, Z, respectively, on some microbiological properties of Turkish White (TW) brined cheese. For each pH, four batches of cheese were produced from: raw milk with no added carbon dioxide (UR), raw milk with carbon dioxide (TR), pasteurised milk with no carbon dioxide addition (UP) and pasteurised milk with carbon dioxide addition (TP). The microbiological analysis of TW brined cheeses was carried out for 90 days of maturation period. Total aerobic mesophilic bacteria, mesophilic lactic acid bacteria, yeasts and moulds and coliform group were determined in control and CO₂ treatment groups. Mesophilic bacteria count was determined as 5.14, 5.29, 5.67 log cfu/g for pH 6.1, 6.2 and 6.3, respectively, in CO₂‐treated raw milk cheeses. Yeasts and moulds reduction increased significantly by applying CO₂ (P < 0.01). For TW cheese samples, the most significant microbial inactivation was detected at sample groups of pH 6.1.     

Combined temperature–time parameters during the pressing of curd as a tool to modulate the oiling-off of Swiss cheese

Oiling-off is essential for the culinary functional properties of hard- and semi-hard cheeses. However, the parameters implied in the mechanisms leading to oiling-off are not well known. In Emmental cheese, a marked change in the supramolecular organization of fat occurs during the pressing of the warm curd and could be related to the oiling-off of cheese. To check this hypothesis and to determine the relative effects of the temperature and pressing strength, twin-cheeses were submitted to various cooling rates after the curd have been dipped from the vat. These cheeses were either pressed or non-pressed. Using this strategy, we showed that a higher heat load yields to larger inclusions of fat in the cheese matrix, which has been characterised using confocal laser scanning microscopy, and to higher oiling-off. The heat load applied to the curd (integral of the temperature vs. time curve) and oiling-off of cheeses aged of 5 days were linearly related with r² = 0.89. In contrast, the pressing strength did not influence oiling-off. As a conclusion, the heat load applied during pressing and acidification could be a tool to modulate the oiling-off of Swiss cheese.     

Use of an exopolysaccharide-producing strain of Streptococcus thermophilus in the manufacture of Mexican Panela cheese

An exopolysaccharide (EPS) producing strain of Streptococcus thermophilus was evaluated for the production of Panela cheese using two total solids milk (TSM) concentrations (12.5 and 17.5 g/100 mL). This ropy strain increased cheese yield; nevertheless, with 12.5 TSM the increment was higher than with 17.5 TSM. Analysis of cheese composition showed that with 12.5 TSM, the ropy strain increased moisture, but did not change the fat or non fat solids on dry weight basis (dwb), suggesting that the increment of the yield is only due to water retention. In 17.5 TSM cheeses the ropy strain caused an increase in the moisture and fat (dwb), suggesting that besides water retention, fat also contributed to the yield. The difference in yield increment could be explained by cheese composition: higher fat content creates a more hydrophobic environment, which would expel more water than the cheese with lower fat content. Electron microscopy showed EPS attached to the protein matrix of the cheeses. In 17.5 TSM cheeses EPS was observed around the milk fat globules (MFG), confirming that higher TSM causes EPS to bind the MFG besides binding the protein matrix, retaining fat within the cheese. Sensory evaluation demonstrated that ropy cheeses were softer and creamier.     

Rennet caseins manufactured from seasonal milks: composition, hydration behaviour and functional performance in pilot-scale manufacture of mozzarella cheese analogues

Compositional and hydration properties of edible rennet caseins prepared from Irish milks over three production seasons were studied. The ash content of the caseins declined during early to mid-lactation and increased sharply in late-lactation. Protein content was independent of season of manufacture, while moisture content showed no clear relationship to season of manufacture. The hydration properties of the rennet caseins on dispersion in a solution of a calcium-sequestering salt were assessed in a simple model system relevant to mozzarella cheese analogue manufacture. The maximum viscosity index reached and the time taken to reach maximum viscosity index on dispersion of rennet casein both decreased as the season of manufacture progressed. Poor performance of rennet caseins in pilot-scale mozzarella cheese analogue manufacture was observed for some caseins manufactured from both early lactation milks and late-lactation milks, while caseins manufactured from mid-lactational milks generally performed well in pilot-scale mozzarella cheese analogue manufacture.     

The technology of low-fat cheese manufacture

Growth in the low-fat cheese market has been slower than would be anticipated on the basis of increased consumer awareness of dietary fat intake. Consumer dissatisfaction with the quality of first-generation low-fat products has highlighted the need for improved technology. Significant advances in understanding the biochemical and physicochemical characteristics of low-fat variants in the past decade have led to novel technological developments. Approaches that have the potential to improve the flavour, texture and functionality of reduced- and low-fat cheese are reviewed here. Topics include the control of processing variables, the selection of appropriate starter and adjunct bacteria, and the use of fat mimetics to improve texture. Factors influencing flavour and texture development in low-fat variants are also considered.