Water quality and taste sensitivity for basic tastes and metallic sensation

The aim of the study was to investigate the influence of water quality on taste sensitivity for basic tastes and metallic sensation. To familiarize subjects with sensory analysis, they were asked to recognize tastes, distinguish between different concentrations of basic tastes, and realize their own taste sensitivity. The International Standard ISO 3972 describes a set of tests to measure taste sensitivity. A “neutral, tasteless, still and odourless water, preferably of known hardness” is recommended for preparing the dilutions and for rinsing the mouth. The standard also recommends a series of dilutions for acid (citric acid), bitter (caffeine), salty (sodium chloride), sweet (sucrose), umami (monosodium glutamate) and metallic (iron(II)sulfate). The question arises if water quality affects taste sensitivity.MethodsTwenty-three female subjects (mean age: 22), who were recruited at the University of Applied Sciences Hamburg, Faculty of Life Sciences, were tested. Deionized water, spring water and tap water were used for taste dilutions. In each experiment, subjects were initially familiarized with the basic tastes.ResultsIn comparison to taste thresholds in spring water, the recognition thresholds are higher using tap water, and lower using deionized water. When using deionized water, sour was detected by all subjects at the lowest concentrations. Iron(II)sulfate could best be matched to metallic sensation in deionized water. Results indicate that taste sensitivity is influenced by water quality.     

Temperature-induced moisture migration in reduced-fat Cheddar cheese

Moisture migration during cooling of 290-kg Cheddar cheese blocks is a problem. The problem is of greater magnitude in reduced and low fat varieties. The objective of this study was to design and evaluate the performance of a laboratory-scale apparatus for simulation of temperature induced moisture migration in 290-kg blocks of Cheddar cheese. Two apparati were designed to produce a systematic temperature gradient in small cheese slabs over a 36-h period to simulate the temperature gradient that develops during cooling of a 290-kg block. One of the apparati was designed to induce a moisture migration downwards with gravity and the other against gravity. The apparati produced moisture migration ranges of 9.7 and 6.4%, for the apparatus to induce moisture migration downwards and upwards, respectively. The moisture moved from areas of warm cheese to areas of cold cheese during cooling, as occurs in 290-kg blocks. These ranges were comparable to those obtained with 290-kg reduced-fat Cheddar blocks. In addition, small but significant differences in pH were created within slabs. The direct effect of the temperature gradient on moisture migration within cheese slabs appeared to be more important than the possible impact of the small pH gradient produced within the cheese by the temperature gradient.     

Yeasts as adjunct starters in matured Cheddar cheese

Debaryomyces hansenii and Yarrowia lipolytica are typical foodborne yeast species frequently associated with dairy products and capable of predominating the yeast composition in such systems. The two species fulfil a number of criteria to be regarded as co-starters for cheesemaking. They are known for their proteolytic and lipolytic activity as well as their compatibility and stimulating action with the lactic acid starter cultures when co-inoculated. Recent studies indicated that yeasts could be included as part of starter cultures for the manufacturing of cheese, enhancing flavour development during the maturation. The potential of D. hansenii and Y. lipolytica as agents for accelerated ripening of matured Cheddar cheese has been evaluated during four cheese treatments. The interaction between the two yeast species and the lactic acid bacteria was surveyed incorporating (i) D. hansenii, (ii) Y. lipolytica, (iii) both species as adjuncts to the starter culture and (iv) a control cheese without any additions for the production of matured Cheddar cheese. The physical and chemical properties of the cheeses were monitored in order to evaluate the contribution of the yeasts to cheese maturation. The yeasts grew in association with the lactic acid bacteria without any inhibition. The yeasts species when individually added contributed to the development of bitter flavours despite accelerated development of strong Cheddar flavours. When both species were incorporated as part of the starter culture, the cheese, however, had a good strong flavour after a reduced ripening period. The cheese retained this good flavour and aroma after 9 months of production. The simultaneous application of D. hansenii and Y. lipolytica as part of the starter culture for the production of matured Cheddar cheese is proposed.     

Identification of bioactive peptides in commercial Cheddar cheese

This study examined the presence of antimicrobial, antioxidant and antihypertensive peptides in three commercially available Australian Cheddar cheeses. Peptide extracts as well as fractionated peptide extracts were examined. Commercial cheese A peptides exhibited the greatest inhibition against Bacillus cereus and also commercial cheese A fractionated peptides greater than 10 kDa showed the highest inhibition against B. cereus. Commercial cheese A peptides also showed the highest inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH), a free radical used to measure antioxidant activity. All cheese fractionated peptides greater than 10 kDa demonstrated higher inhibition of DPPH after fractionation. Antihypertensive peptides were determined by inhibition of the angiotensin-converting enzyme (ACE). Overall, commercial cheese A had the lowest concentration required to inhibit ACE and commercial cheese A fractionated peptides lower than 5 kDa had the lowest inhibition after fractionation. These preliminary findings suggest that peptide extracts of three commercial Australian Cheddar cheeses exhibit antimicrobial, antihypertensive and antioxidant properties.     

Prediction of maturity and sensory attributes of Cheddar cheese using near-infrared spectroscopy

Twenty-four experimental Cheddar cheeses were produced using 5 renneting enzymes and stored at 4 °C for up to 9 months. At 2, 4, 6 and 9 months, cheeses were analysed for sensory attributes (“crumbly”, “fragmentability”, “firmness”, “rubbery”, “gritty/grainy”, “moist”, “chewy”, “mouthcoating”, “greasy/oily”, “melting” and “massforming”) by a trained panel of 10 assessors. Near-infrared (750–2498 nm) reflectance spectra were recorded contemporaneously. Predictive models for the sensory attributes and age (months) were developed by partial least-squares (PLS) regression; raw, derivatised and scatter-corrected spectral data were investigated. As a general rule, the most accurate models were produced by spectral data in the range 750–1098 nm after a 2nd derivatisation step. Age was predicted with a root mean square error of cross-validation (RMSECV) equal to 0.61; sensory attributes successfully modelled and their respective RMSECV values were “crumbly” (2.3), “rubbery” (3.4), “chewy” (4.0), “mouthcoating” (5.0) and “massforming” (4.1). These models are sufficiently accurate to be industrially useful.     

Low‐fat Cheddar cheese made using microparticulated whey proteins: Effect on yield and cheese quality

Influence of different levels (0, 0.15, 0.35 or 0.50%) of microparticulated whey protein (MWP) on yield and quality of low‐fat (~7.3 g/100 g) Cheddar cheese was investigated. MWP improved cheese yield due to the water‐binding ability of denatured whey protein. MWP addition decreased meltability but improved the textural properties beneficial for shredding and slicing, by decreasing sensory firmness. The results emphasise the role of MWP as an inert filler within cheese matrix, in improving cheese yield and creating a softer texture without compromising the sensory or overall quality of cheese, even with moisture increases in 0.35 or 0.50% MWP cheeses.     

Application of salt whey in process cheese food made from Cheddar cheese containing exopolysaccharides

The objective of this work was to use salt whey in making process cheese food (PCF) from young (3-wk-old) Cheddar cheese. To maximize the level of salt whey in process cheese, low salt (0.6%) Cheddar cheese was used. Because salt reduction causes undesirable physiochemical changes during extended cheese ripening, young Cheddar cheese was used in making process cheese. An exopolysaccharide (EPS)-producing strain (JFR) and a non-EPS-producing culture (DVS) were applied in making Cheddar cheese. To obtain similar composition and pH in the EPS-positive and EPS-negative Cheddar cheeses, the cheese making protocol was modified in the latter cheese to increase its moisture content. No differences were seen in the proteolysis between EPS-positive and EPS-negative Cheddar cheeses. Cheddar cheese made with the EPS-producing strain was softer, and less gummy and chewy than that made with the EPS-negative culture. Three-week-old Cheddar cheese was shredded and stored frozen until used for PCF manufacture. Composition of Cheddar cheese was determined and used to formulate the corresponding PCF (EPS-positive PCF and EPS-negative PCF). The utilization of low salt Cheddar cheese allowed up to 13% of salt whey containing 9.1% salt to be used in process cheese making. The preblend was mixed in the rapid visco analyzer at 1,000 rpm and heated at 95°C for 3 min; then, the process cheese was transferred into copper cylinders, sealed, and kept at 4°C. Process cheese foods contained 43.28% moisture, 23.7% fat, 18.9% protein, and 2% salt. No difference in composition was seen between the EPS-positive and EPS-negative PCF. The texture profile analysis showed that EPS-positive PCF was softer, and less gummy and chewy than EPS-negative PCF. The end apparent viscosity and meltability were higher in EPS-positive PCF than in EPS-negative PCF, whereas emulsification time was shorter in the former cheese. Sensory evaluation indicated that salt whey at the level used in this study did not affect cheese flavor. In conclusion, process cheese, containing almost 13% salt whey, with improved textural and melting properties could be made from young EPS-positive Cheddar cheese.     

Isomaltooligosaccharide increases the Lactobacillus rhamnosus viable count in Cheddar cheese

Five batches of Cheddar cheese were manufactured containing different levels of isomaltooligosaccharide (IMO) and a probiotic strain of Lactobacillus rhamnosus to study the effect of IMO on the survival of starter lactococci and probiotic micro‐organisms, on proteolytic patterns, cheese composition and sensory properties. The cheese was exposed to conditions simulating those found in the gastrointestinal tract to evaluate the survival of Lb. rhamnosus. Results demonstrated that the addition of Lb. rhamnosus and IMO did not affect the main compositional variables of Cheddar cheese. The counts of starter culture and probiotic organisms increased in cheese which contained Isomaltooligosaccharide (Batches 3, 4 and 5) more than in the control (Batches 1 and 2) during the fermentation. The probiotic counts in fresh cheese (B‐4) was 9.23 log₁₀ cfu/g which was more than one log cycle greater than in the control (B‐2). The probiotic counts remained above 8 log₁₀ cfu/g at the end of the manufacturing process. Primary proteolysis was not affected by the addition of probiotic bacteria and IMO, but the level of secondary proteolysis was slightly higher compared with the control group. The addition of IMO improved the texture and sensory quality of the cheese and the probiotic bacterium had the same effect. Under conditions that simulated the gastrointestinal tract, the probiotic bacteria in cheese (B‐4) exhibited good survival and remained above the recommended 6–7 log₁₀ cfu/g.     

Gas-flushed packaging contributes to calcium lactate crystals in Cheddar cheese

Gas-flushed packaging is commonly used for cheese shreds and cubes to prevent aggregation and loss of individual identity. Appearance of a white haze on cubed cheese is unappealing to consumers, who may refrain from buying, resulting in lost revenue to manufacturers. The objective of this study was to determine whether gas flushing of Cheddar cheese contributes to the occurrence of calcium lactate crystals (CLC). Cheddar cheese was manufactured using standard methods, with addition of starter culture, annatto, and chymosin. Two different cheese milk compositions were used: standard (lactose:protein = 1.47, protein:fat = 0.90, lactose = 4.8%) and ultrafiltered (UF; lactose:protein = 1.23, protein:fat = 0.84, lactose = 4.8%), with or without adjunct Lactobacillus curvatus. Curds were milled when whey reached 0.45% titratable acidity, and pressed for 16 h. After aging at 7.2°C for 6 mo, cheeses were cubed (1 × 1 × 4 cm) and either vacuum-packaged or gas-flushed with carbon dioxide, nitrogen, or a 50:50 mixture of carbon dioxide and nitrogen, then aged for an additional 3 mo. Heavy crystals were observed on surfaces of all cubed cheeses that were gas-flushed, but not on cheeses that were vacuum-packaged. Cheeses without Lb. curvatus exhibited l(+)-CLC on surfaces, whereas cheeses with Lb. curvatus exhibited racemic mixtures of l(+)/d(−)-CLC throughout the cheese matrices. The results show that gas flushing (regardless of gas composition), milk composition, and presence of nonstarter lactic acid bacteria, can contribute to the development of CLC on cheese surfaces. These findings stress the importance of packaging to cheese quality.     

长春地区消费者干酪口味调查分析报告

通过对长春地区650余名消费者干酪风味、口感和营养需求等的调查,分析了不同年龄段的消费群体对干酪口味的需求.调查结果表明,大多数消费者没有食用过真正的西式干酪,在干酪的口味方面普遍喜欢风味淡、盐分低、质地柔软的新鲜干酪、软质干酪或再制干酪.本调查的结果为开发适合国人口味的干酪提供了依据.     

Microbiological quality of shredded Cheddar cheese packaged in modified atmospheres

The microbiological quality of shredded Cheddar cheese packaged in different modified atmospheres with and without oxygen scavengers included in the packaging film was studied with the aim of determining how modified air packaging would affect the mould species present on shredded Cheddar cheese. The film with oxygen scavengers was more effective than the control film against mould growth, whereas the 73% CO₂/27% N₂ atmosphere resulted in the cheese with the best microbiological qualities. The three modified atmospheres and the packaging film influenced the mycoflora of shredded Cheddar cheese as the mould species isolated initially differed, from those isolated at 16 weeks in the six treatments. This study demonstrated that O₂ scavengers were effective in controlling the growth of moulds on shredded Cheddar cheese.     

Compositional factors associated with calcium lactate crystallization in smoked Cheddar cheese

Previous researchers have observed that surface crystals of calcium lactate sometimes develop on some Cheddar cheese samples but not on other samples produced from the same vat of milk. The causes of within-vat variation in crystallization behavior have not been identified. This study compared the compositions of naturally smoked Cheddar cheese samples that contained surface crystals with those of samples originating from the same vat that were crystal-free. Six pairs of retail samples (crystallized and noncrystallized) produced at the same cheese plant on different days were obtained from a commercial source. Cheese samples were 5 to 6 mo old at the time of collection. They were then stored for an additional 5 to 13 mo at 4°C to ensure that the noncrystallized samples remained crystal-free. Then, the crystalline material was removed and collected from the surfaces of crystallized samples, weighed, and analyzed for total lactic acid, l(+) and d(−) lactic acid, Ca, P, NaCl, moisture, and crude protein. Crystallized and noncrystallized samples were then sectioned into 3 concentric subsamples (0 to 5 mm, 6 to 10 mm, and greater than 10 mm depth from the surface) and analyzed for moisture, NaCl, titratable acidity, l(+) and d(−) lactic acid, pH, and total and water-soluble calcium. The data were analyzed by ANOVA according to a repeated measures design with 2 within-subjects variables. The crystalline material contained 52.1% lactate, 8.1% Ca, 0.17% P, 28.5% water, and 8.9% crude protein on average. Both crystallized and noncrystallized cheese samples contained significant gradients of decreasing moisture from center to surface. Compared with noncrystallized samples, crystallized samples possessed significantly higher moisture, titratable acidity, l(+) lactate, and water soluble calcium, and significantly lower pH and NaCl content. The data suggest that formation of calcium lactate crystals may have been influenced by within-vat variation in salting efficacy in the following manner. Lower salt uptake by some of the cheese curd during salting may have created pockets of higher moisture and thus higher lactose within the final cheese. When cut into retail-sized chunks, the lower salt, higher moisture samples contained more lactic acid and thus lower cheese pH, which shifted calcium from the insoluble to the soluble state. Lactate and soluble calcium contents in these samples became further elevated at the cheese surface because of dehydration during smoking, possibly triggering the formation of calcium lactate crystals.     

Factors affecting calcium lactate and liquid expulsion defects in Cheddar cheese

This paper summarizes the results of 2 studies designed to investigate the influence of several manufacturing and curing treatments on the appearance of Cheddar cheese defects. Specifically, 2 defects, calcium lactate crystal formation and the expulsion of free liquid (weeping) were monitored in Cheddar cheese. Both studies were conducted at a commercial cheese manufacturing facility that produces Cheddar in 18.14-kg (40-lb) blocks. In the first study we monitored cheese calcium, both total and soluble during manufacture and early curing. In the second study we measured cheese pH from 3 d through 8 mo, as well as some factors that are influenced by cheese pH. Early cheese pH (3 d to 7 d) patterns were used to select vats of cheese for retail packaging. Mild Cheddar packaged at 30 d postmanufacture and sharp Cheddar packaged at 8 mo postmanufacture from the same vats were monitored for the incidence and severity of the defects. Our results indicated that factors measured in early stages of manufacture and curing (less than 7 d) such as cheese pH at mill, lactic acid concentration, nonprotein nitrogen, and calcium (total and soluble) in cheese did not correlate with the appearance of either calcium lactate or expulsion of free liquid in packaged cheeses. Factors including pH, lactic acid concentrations, and soluble calcium measured during curing (greater than 7 d) of cheese were found to be statistically significant in the development of defects and appeared to be associated with use of specific starter culture groups. In the study, 5 different starter culture groups, each consisting of a 4-strain blend of Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis, were used to manufacture the cheeses. Cheese manufactured with one particular culture group showed no incidence of calcium lactate crystal formation or weeping during curing and shelf-life of cheeses in this study. This starter group also generated the least amount of pH change in cheese during the first month of curing. From these results we conclude that starter culture group, more than any other factor measured, played an important role in the development of calcium lactate and liquid expulsion defects in Cheddar cheese. Starter culture group appeared to strongly influence cheese pH, lactic acid, and soluble calcium concentrations during curing and storage.     

Identification of aroma-active compounds in Cheddar cheese imparted by wood smoke

Cheddar cheese is the most popular cheese in the United States, and the demand for specialty categories of cheese, such as smoked cheese, are rising. The objective of this study was to characterize the flavor differences among Cheddar cheeses smoked with hickory, cherry, or apple woods, and to identify important aroma-active compounds contributing to these differences. First, the aroma-active compound profiles of hickory, cherry, and apple wood smokes were analyzed by solid-phase microextraction (SPME) gas chromatography-olfactometry (GCO) and gas chromatography-mass spectrometry (GC-MS). Subsequently, commercial Cheddar cheeses smoked with hickory, cherry, or apple woods, as well as an unsmoked control, were evaluated by a trained sensory panel and by SPME GCO and GC-MS to identify aroma-active compounds. Selected compounds were quantified with external standard curves. Seventy-eight aroma-active compounds were identified in wood smokes. Compounds included phenolics, carbonyls, and furans. The trained panel identified distinct sensory attributes and intensities among the 3 cheeses exposed to different wood smokes (P < 0.05). Hickory smoked cheeses had the highest intensities of flavors associated with characteristic “smokiness” including smoke aroma, overall smoke flavor intensity, and meaty, smoky flavor. Cherry wood smoked cheeses were distinguished by the presence of a fruity flavor. Apple wood smoked cheeses were characterized by the presence of a waxy, green flavor. Ninety-nine aroma-active compounds were identified in smoked cheeses. Phenol, guaiacol, 4-methylguaiacol, and syringol were identified as the most important compounds contributing to characteristic “smokiness.” Benzyl alcohol contributed to the fruity flavor in cherry wood smoked cheeses, and 2-methyl-2-butenal and 2-ethylfuran were responsible for the waxy, green flavor identified in apple wood smoked cheeses. These smoke flavor compounds, in addition to diacetyl and acetoin, were deemed important to the flavor of cheeses in this study. Results from this study identified volatile aroma-active compounds contributing to differences in sensory perception among Cheddar cheeses smoked with different wood sources.     

Effect of commercial lipolytic enzymes on flavour development in Cheddar cheese

The addition of commercial lipolytic enzymes to experimental Cheddar cheese accelerated the liberation of free fatty acids during ripening. The substrate specificity of the added enzymes generally governed the chain lengths of the free fatty acids in the cheeses. None of the enzymes accelerated the formation of typical flavour in either the presence or the absence of a flavour-enhancing proteinase, but higher addition levels produced lipolytic rancidity.     

Population dynamics of coliforms in a commercial Cheddar cheese production facility

The detection of coliforms in young cheese is a potential indication of undesirable microbial growth within the processing environment. The aim of this study was to investigate sources and conditions that lead to the intermittent detection of coliforms (1–3 log cfu/g) in young Cheddar cheese at a single commercial facility. Analysis of historical production data, in combination with iterative investigative sampling events, was performed to determine coliform levels in milk, whey, curd, and surfaces at the beginning, middle, and end of the production day. After sanitation, conveyor belt pieces from the draining and matting conveyor (DMC) were collected and evaluated for bacterial survivors using culture-based methods and scanning electron microscopy. Production data analysis indicated that cheese produced later in the production day (≥16 h) was significantly more likely to test positive for coliforms than cheese made earlier in the production day (<12 h). Enumeration of coliforms in raw and heat-treated milk demonstrated that the subpasteurization thermal treatment (67–70°C, 26–28 s) was effective at reducing, but not eliminating, coliforms. Repeated sampling identified the DMC, particularly the drain belt and belt 1, as a critical area that supported coliform growth during the production day. Coliform levels in whey entering the weir maintained a level of <1 cfu/mL throughout production; however, coliform levels in whey below the drain belt increased from <1 cfu/mL at midday (8 h) to 5.04 log cfu/mL by the end of the production day (~18 h). Routine sanitation inside the DMC resulted in undetectable coliform levels on easily accessible surfaces. However, enrichment and scanning electron microscopy of belt sections revealed pockets of viable coliforms and other bacteria in cracks and defects in conveyor belts, indicating that sanitation did not eliminate all viable bacteria. Low levels of coliforms are present in heat-treated milk and survive sanitation in the DMC and could serve as the initial seed for high levels of coliforms at the end of the production day.