Evaluation of processed cheese viscoelastic properties during sterilization observed in situ

Sterilized processed cheese is a specific dairy product with a prolonged shelf life intended for regular retail offer but also as food provisions for armies during peacetime, as well as during crisis and emergency situations, and for storage in state material reserves. Storage requirements are usually defined as ≤25°C for at least 24 mo. One of the ways to achieve such a shelf life is sterilization. Therefore, the aim of the work was to describe, for the first time in the available scientific literature, in situ changes in the viscoelastic properties of spreadable melt (34% wt/wt DM content, 45% wt/wt fat in DM content, and 14% wt/wt protein content) during an increase in temperature (target temperature 122°C), holding at sterilization temperature (20 min) and subsequent cooling (to ~30°C). While increasing to the target sterilization temperature, a significant decrease occurred in the storage and loss moduli values. Both moduli started to increase again during the target sterilization temperature period and during the whole cooling phase. The values of the storage and loss moduli were significantly higher at the end of the cooling of the sterilized product, and conversely, the phase angle value was lower compared with the melt before sterilization. As a result of sterilization, an increase occurred in the levels of markers of the Maillard reaction complex and lipid oxidation processes. The value of hardness, corrected stress, and elongational viscosity also increased compared with nonsterilized products. As a result of sterilization, the flavor worsened and sterilized processed cheeses showed darker (brownish) color. However, even after sterilization, the products were evaluated as acceptable for consumers and maintained their spreadability.     

Influence of Different Factors on Firmness and Color Evolution During the Storage of Persimmon cv. 'Rojo Brillante'

‘Rojo Brillante’ persimmons were harvested in 2 different dates, early and late, and then submitted to 1‐methylcyclopropene (1‐MCP) treatment (500 nL/L) before stored at 1 or 15 °C up to 50 or 30 d, respectively. The influence of harvest date, 1‐MCP treatment, orchard, storage time, and temperature on firmness loss and color evolution during storage of ‘Rojo Brillante’ persimmon was studied. Statistical models that allowed the prediction of these 2 quality parameters during the storage, as well as the modeling of the behavior of both of them, were also evaluated. The softening, as a consequence of chilling sensitiveness when stored at 1 °C, was more accentuated in the early harvested fruit. In storage at 15 °C, also, the firmness loss was faster in fruit harvested earlier. 1‐MCP treatment drastically reduced chilling injury (CI) symptoms at 1 °C and retarded firmness loss at 15 °C, both of these effects being dependent on harvest date. The model presented to study the firmness and color relationship offers an important tool to predict firmness from fruit color measurements.     

The influence of storage temperature and storage time on color stability,retail properties and case-life of retail-ready beef

Steaks from three different muscles were either vacuum or carbon dioxide packed and stored for up to 24 weeks at three different storage temperatures (−1.5, 2, or 5 °C). Following storage, they were displayed for up to 30 h. CIE color coordinates, the oxidative states of myoglobin and pH were measured and muscle color, surface discoloration, retail appearance, and odor were evaluated prior to storage and during display (0, 1, 2, 4, 6, 24 and 30 h), and/or immediately prior to and following display. Prior to display, pH was negatively related to duration of storage, and samples stored at −1.5 °C had the highest and samples stored at 5 °C, had the lowest pH. Perception of muscle color was influenced by duration of storage and display, but lower storage temperatures appeared to produce a stabilizing effect. Both lightness of muscle color and deoxymyoglobin content were apparently not influenced by storage temperature or duration of storage or display. Both oxymyoglobin (OMB) and redness, as defined by CIE a* values, were lost progressively during storage and display, but this loss was progressively lower as storage temperature decreased. Yellowness of muscle color, as defined by CIE b* values, generally decreased as storage was prolonged, and this decrease was observed more quickly at higher storage temperatures. Surprisingly, b* values were not related to duration of display. Both surface discoloration and metmyoglobin (MMB) content increased progressively during storage and display. Samples stored at 5 °C displayed the most surface discoloration, while samples stored at −1.5 °C contained the least MMB and displayed the least surface discoloration. Retail appearance deteriorated progressively during storage in all samples stored at 2 and 5 °C and in samples stored at −1.5 °C, which were displayed for at least 24 h. Retail appearance also deteriorated progressively during display in samples stored at −1.5 and 2 °C for three weeks or longer and in samples stored at 5 °C for 0 to 15 and 24 weeks. In unstored samples, samples to be stored at −1.5 °C generally received the lowest retail appearance scores, but after prolonged storage and display, samples stored at −1.5 °C received higher retail appearance scores than samples stored at 5 °C, particularly when samples were stored for 12 weeks or longer and displayed for 1 h or more. Odor deteriorated progressively during storage when measured both prior to display and after 30 h of display. In samples stored for three weeks or longer, samples stored at −1.5 °C generally received the lowest odor scores and were perceived to have the least prevalent off-odors. Samples stored at −1.5 °C maintained a retail case-life of 30 h, when stored for up to 17 weeks, while samples stored at 2 and 5 °C maintained a retail case-life of 30 h, when stored for only eight and seven weeks, respectively. Consequently, storage life can be more than doubled by storage at subzero temperatures (−1.5 °C).     

Physical and Sensory Properties of Block Processed Cheese with Formulated Emulsifying Salt Mixtures

Abstract

Various emulsifying salt mixtures were used in making block type processed cheeses. Ras cheese was used as the cheese base with two salt mixtures: (i) Na-diphosphate + Na-polyphosphate + Na-tripolyphosphate and (ii) Na-poly-phosphate + Na-citrate + Na-orthophosphate + Na-diphosphate comparing to commercial salts Joha SE and PZO respectively. The resultant processed cheeses were analyzed when fresh and monthly during storage at 7 and 20°C for water activity (a _w ), oil separation, meltability, flow behavior, color parameters, and sensory properties. There were no significant differences in water activity values among all treatments. The differences were significant in oil index and meltability values. The samples exhibited different shear stress values and it was highest in treatments with commercial salts. Consistency coefficient (k-value) of processed cheese samples was affected by emulsifying salt mixture being almost two folds higher with salt mixtures (i) than those of salt mixtures (ii). The color parameters L, a, b, Chroma and hue angle showed slight differences among treatments and the cheese was shinier and whiter with increasing pyrophosphate content in the salt mixture. The stored samples became less white especially when stored at room temperature (20°C). Sensory evaluation showed that all cheeses were acceptable but the most acceptable samples were produced with mixtures in the ratio of (i) 30:40:30 and (ii) 50:20:20:10.     

The impact of collagen on softening of grass carp (Ctenopharyngodon idella) fillets stored under superchilled and ice storage

The objective of this work was to study the impact of collagen on softening of grass carp (Ctenopharyngodon idella) fillets during chilled storage. The fillets were stored under superchilling (?1.5 ± 0.2 °C) and with ice (0.2 ± 0.1 °C) for 21 days, and texture properties, collagen and the related enzyme activities were measured. Results showed that firmness and collagen content were strongly influenced by storage temperature and time. Fillet firmness decreased by 32.3% (superchilling) and 49.6% (ice stored) of the initial values after 3 days of storage, respectively. Total collagen content decreased with time, but different collagen fractions showed variations. Collagen degraded to different extents depending on storage conditions as indicated by SDS‐PAGE and amino acid analysis. In addition, collagenase activity declined significantly during the first 3 days, followed by a slow increase. This study demonstrated that collagen degradation was involved in grass carp fillet softening and provided useful information for fillet quality improvement.     

Employing an intelligence model and sensitivity analysis to investigate some physicochemical properties of coated bell pepper during storage

The objectives of this work were to study the effects of three different coatings (gum Tragacanth, sesame oil and gum Tragacanth–sesame oil), temperature and time on shelf life of bell pepper. Moisture reduction, shrinkage as well as firmness and colour changes were studied during 30 days at 4, 10, 15 and 23 °C. Results of this study showed that bell peppers treated with gum Tragacanth at higher temperatures, such as 10 °C, had good quality up to 30 days of storage. However, sharp changes in physicochemical characters were observed in bell peppers stored at 23 °C. In order to predict moisture reduction, shrinkage, firmness and colour changes genetic algorithm–artificial neural network model was developed. It was found that artificial neural network with eight hidden neurons truly could predict the physicochemical changes of bell pepper during storage (R² > 0.9598). The results of sensitivity analysis showed that shrinkage percentage and also changes of firmness and colour were very sensitive to storage time, while storage temperature had the most effect on moisture reduction.     

Addition of olein from milk fat positively affects the firmness of butter

Butter is highly valued for its characteristic flavor and aroma; however, it has the disadvantage of unsatisfactory spreadability at low temperatures. The functional characteristics of butter can be modified by changing its composition or physical structure. The objective of this study was to evaluate the effect of olein on structure and composition of butter. Olein was obtained by two stage dry fractionation process of the anhydrous milk fat (AMF) and added to commercial cream prior to butter manufacture. The fractions were characterized for triacylglycerols composition, solid fat content, crystallization isotherm, and thermal behavior. Butter was manufactured using commercial cream or cream containing 50% olein. Butter samples were characterized for physicochemical composition, instrumental color, crystallization parameters, and firmness after 1 and 7 days of storage at 10 °C. The firmness of butter subjected to room temperature was also evaluated. Butter containing olein differed significantly from the control and had darker yellow color, higher crystallization time, and lower solid fat content after 120 min at 15 °C, and hence lower firmness after 1 and 7 days of refrigerated storage. Although lower firmness was observed over time for all samples at room temperature, butter containing olein exhibited lower firmness after both 1 and 7 days, thus suggesting changes in organization of solid fat crystal network in the liquid fat. The addition of olein to butter allowed obtaining a softer product, with more intense color and possible nutritional benefits due to the medium chain triglycerides and higher carotene levels.     

Color and Texture of Acidified Ripe Olives in Pouches

The effects of pouch material (aluminum, plastic), packing pH (3.8,4.3), acidifying compound (lactic, gluconic), and storage temperature were tested on polyphenol content and color of holding brines, surface color, and firmness of ripe olives. Using pouches of plastic films, pH 4.3–4.0 holding solution, and lactic or gluconic acid products with color and texture similar to traditional canned ripe olives were produced. They could be properly stored at room temperature (25°C). As storage temperature rose, color improved but texture was seriously degraded at 50°C.     

How do different cooling temperatures affect the characteristics of set-type yoghurt gel?

The impact of cooling temperatures on gel characteristics of set-type yoghurts was investigated through 28 days of storage. Yoghurt samples were cooled at four different temperatures (−10 °C, −5 °C, 0 °C, 4 °C) after incubation until the central temperature of yoghurt cups reached 4 °C. Cooling temperature and storage period were determined as significant factors affecting the yoghurt gel characteristics (p < 0.05). Yoghurts cooled at 0 °C clearly differed from the other yoghurts in terms of gel firmness and consistency. Confocal images of yoghurts cooled at 0 °C showed more homogeneous protein matrix than the other samples. Microbial counts and the acidity of the yoghurt samples increased with storage period. Textural parameters, water holding capacity and susceptibility to syneresis increased until 14th day of storage and then decreased. Sensory analysis of yoghurt samples confirmed the results obtained by microbiological and textural measurements.     

Efficacy of bovicin HC5 and nisin combination against Listeria monocytogenes and Staphylococcus aureus in fresh cheese

Fresh and soft cheeses provide a suitable medium for the growth of many microorganisms and have been frequently associated with foodborne diseases. This study aimed to evaluate the effects of the bacteriocins bovicin HC5 and nisin on Listeria monocytogenes and Staphylococcus aureus in Minas Frescal cheese, a traditional Brazilian fresh product. The cheese was inoculated with 10⁴ CFU g^?1 of both pathogens, and the bacteriocins were added at 600 AU g^?1 of each one. After 9 days of storage at 4 °C, L. monocytogenes Scott A were not detected in 25 g samples. Although the bacteriocins reduced the population of S. aureus ATCC 6538, increasing numbers were detected after 15 days of storage at 4 °C. Staphylococcal enterotoxin C was detected in cheeses added of bacteriocins and stored under abusive temperature of 15 °C. The results demonstrate the potential application of combination of bovicin HC5 and nisin in controlling the pathogens growth assessed in Minas Frescal cheese.     

Changes in physicochemical characteristics of rice during storage at different temperatures

This study investigated the changes in the physicochemical properties of rice during storage at different temperatures. Milled rice stored at high temperatures showed higher fat acidity than rice stored at low temperatures. Although the moisture content of milled rice stored at 30 °C and 40 °C decreased below 15.5% (15.33% and 15.22%, respectively) after 1 month, adequate values were maintained with storage at 4 °C for 3 months (15.50%) and at 20 °C for 2 months (15.53%). Rice stored at low temperatures retained its white coloration, whereas low color retention values were obtained at higher storage temperatures. Peak viscosity increased during 4 months of storage and larger changes were found at higher storage temperatures. Breakdown decreased and setback increased with storage, regardless of storage temperatures. Storage at higher temperatures increased cohesiveness and hardness in compared with storage at lower temperatures. High temperatures also led to a decrease in adhesiveness with age. High temperatures (30 °C and 40 °C) significantly decreased all sensory values even after 1 month of storage. These results are similar to those obtained in an analysis of cooked rice texture. The results of this study indicate that storage temperature is an important factor affecting the physicochemical properties of rice. Short storage periods below room temperatures are recommended to maintain rice quality.     

Quantification of Visual Characteristics of Whipped Cream by Image Analysis and Machine Vision: Method Development

The appearance (color, shine, surface roughness, bumpiness, view area, height) of whipped cream samples change with time. Quantitative methods based on image analysis were developed to measure these parameters in cream samples stored at 3 temperatures (room temperature, 10 °C and 2 °C) for up to 24 h. There was a small decrease in L* and a* values over time, and a significant increase in b* values. ΔE values suggest that these color changes are significant and observable (2.96 for room temperature, 9.46 for 10 °C, 12.6 for 2 °C). Difference between polarized and nonpolarized images was used to quantify shine. The length of a laser line over the cream sample was measured to quantify the change in bumpiness of the surface (33.8%, 41.78%, and 33.27% reduction in laser line length for room temperature, 10 °C, and 2 °C, respectively). For room temperature stored samples, most changes occurred during the first 5 min. For samples stored at 10 °C and 2 °C, most changes occurred during the first 30 min. Turn angles data did not provide useful information. The changes in view area depended on temperature: at room temperature the area increased over time, at 10 °C it increased first then decreased; at 2 °C the view area decreased over time. Correlation of the results of these methods with sensory evaluation can make the evaluation of the appearance of whipped cream more objective, repeatable, and quantitative.     

Changes in antioxidants and taste-related compounds content during cold storage of fresh-cut red sweet peppers

Changes in antioxidants (ascorbic acid, phenolic compounds and carotenoids) and in taste-related compounds (sugars and organic acids) content were monitored in fresh-cut red sweet peppers (Capsicum annuum L., local ecotype “Peperone Cornetto di Pontecorvo”) during 9 days of cold storage. Pepper slices were placed in polystyrene trays, wrapped with a polyvinyl chloride film, and stored at 4 °C or at 8 °C; besides, to evaluate the effect of a prestorage hot water treatment, half of the slices were subjected to a dipping treatment in water at 53 °C for 4 min, before packaging and storage. During storage limited changes in O₂ and CO₂ concentrations were observed within all packages. Storage temperature strongly affected weight loss: at the end of the storage time it was <3 and >10% in fruits stored at 4 and 8 °C, respectively. Sugars (glucose and fructose) content showed a significant increase (+11%) only in fruits stored at 8 °C; this change was due to a concentration effect associated to water loss. A higher increase (+23 and +17% in fruits stored at 8 and 4 °C) was observed in organic acids (citric and malic) content. Minimal processing and storage produced only a quite limited degradation of ascorbic acid. Both hydroxycinnamic acid derivatives and flavonoids accumulated in fruits stored at 8 °C (and not heat treated), whereas at 4 °C phenolics accumulation appeared to be partially inhibited. All the main carotenoids (capsanthin, cucurbitaxanthin A, zeaxanthin, β-carotene and β-cryptoxanthin) markedly accumulated in fruits stored at 8 °C (not heat treated), and showed a general decrease at 4 °C. Hot water treatment did seem to affect organic acids metabolism, though it did not promote ascorbic acid degradation. In addition, it inhibited both phenolics and carotenoid accumulation in fruits stored at 8 °C.     

Cutting Shape and Storage Temperature Affect Overall Quality of Fresh-cut Papaya cv. 'Maradol'

: The effect of cutting shape (cubes or slices) and storage temperature (5 °C, 10 °C, and 20 °C) on overall quality of fresh‐cut papaya were investigated. CO₂ production, color, firmness, total soluble solids (TSS), weight loss, overall quality, ascorbic acid, β‐carotene, and antioxidant capacity were evaluated as a function of shelf life. CO₂ production was high on day 0 for cubes and slices with an average of 150 and 100 mL/ kg/h, respectively. Storage temperature did not affect color changes; however, lower temperatures prevented loss of firmness. Fresh‐cut papaya stored at 20 °C showed the lowest TSS value and the highest weight losses. Shelf life based on visual quality ended before significant losses of total ascorbic acid, b‐carotene, and antioxidant capacity occurred. In general, quality parameters were not affected by shape. However, slices stored at 10 °C and 5 °C had a shelf life of 1 d and 2 d longer than cubes, respectively.     

Effect of hot air on Deglet Noor palm quality parameters and on Ectomyelois ceratoniae

Insect infestation caused by Ectomyelois ceratoniae or carob moth is one of the main postharvest problems that lead to a decrease of marketable quality of dates. The control of carob moth is a mandatory process for exported fruits, and the main chemical method used to prevent pest diseases of palm date is methyl bromide. However, its use is being restricted due to direct, harmful effects to the environment, and indirect effects on humans. Hot air treatments (HATs) could be physical alternatives to methyl bromide and other chemicals. Three HATs (55 °C for 30 min, 60 °C for 15 min, 60 °C for 20 min) were studied on Deglet Noor date fruits when stored for 45 d at 2 °C followed by a retail period of 4 d at 23 °C. The results showed that the use of HATs led to 100% E. ceratoniae larvae mortality in naturally-infested date. These HATs did not cause any damage on fruit quality and reduced mesophilic bacterial counts (<1 log CFU g⁻¹). These HATs, especially the combination of highest temperature and longer time of application (60 °C for 20 min), decreased the antioxidant activity (25% in DPPH and 14% in FRAP assay). Storage time also had a significant impact, reducing color (h°), antioxidant activity, and total phenolic content of date fruits (39%). When this storage was accompanied by a retail period at 23 °C, the firmness and sensorial parameters of date fruits was significantly reduced. Nevertheless, all date fruits from HATs and control treatments maintained their marketability quality for 45 d at 2 °C followed by a retail period of 4 d at 23 °C. Results show that HATs are a physical, non-chemical, treatment for E. ceratoniae larvae mortality that maintained date fruits' postharvest quality.     

Influence of CMC‐ and guar gum‐based silver nanoparticle coatings combined with low temperature on major aroma volatile components and the sensory quality of kinnow (Citrus reticulata)

Aroma profile and organoleptic quality of CMC‐ and guar gum‐based silver nanoparticle‐coated kinnow (Citrus reticulata cv. Blanco) was evaluated for 120 days at 4 °C and 10 °C, 85–95% relative humidity. Loss in three major aroma‐active volatile compounds (limonene, linalool and γ‐terpinene) was determined after every 15 days by GC‐MS. Sensory quality of coated and uncoated fruit stored at 10 °C was declined during storage. Twenty five volatile aroma compounds were identified in fresh kinnow juice. Guar gum‐Ag coatings and 4 °C storage has significantly reduced losses of limonene, linalool and γ‐terpinene contents from 91 to 23%, 99 to 10% and 97 to 29% respectively as compared to uncoated fruit stored at 10 °C. Study suggests that CMC‐ and guar gum‐based silver nanoparticle‐coated kinnow stored at 4 °C has preserved the fruit aroma and sensory quality for 120 days.     

Effect of concentrated plum juice on physicochemical and sensory properties of yoghurt made at bench top scale

Yoghurt with 9% (v/v) of plum juice concentrate (PJC) was stored for 24 days in darkness at 6 °C. Titratable acidity and pH were similar in all samples during storage. The firmness was in the range of 1.7–2.3 N and correlated with total solids of the mixes (R² = 0.982). The sample with PJC and 5.33% (w/v) nonfat dry milk had the highest firmness and the weakest creaminess. The colour in PJC yoghurt was stable during the first seven days of storage. In the ranking test for acceptability, there were no significant differences (P ≤ 0.05) between the yoghurts.     

Shelf Life of Pretreated Dried Tomato

Determining the shelf life has become a factor of major importance in the development of foods designed to meet consumer demands in terms of quality and safety. The goal of the present study was to investigate the shelf life of vacuum-packed dried tomatoes, stored at both room and refrigeration temperature (4 °C) for a period of 180 days. The following determinations were performed during the storage period studied: microbiological analysis, instrumental color, lycopene, and ascorbic acid. Sorption isotherms were determined at both temperatures (room temperature and 4 °C). The microbiological quality of vacuum-packed dried tomatoes remained unchanged during 180 days for the refrigerated samples and 90 days for the samples stored at room temperature. The rate constant (k) of lycopene degradation of the refrigerated samples and the samples stored at room temperature was 3.209 × 10⁻⁵ and 12.994 × 10⁻⁵/day, respectively. The rate constant (k) of ascorbic acid degradation was 3.339 × 10⁻⁴/day for cold storage and 76.655 × 10⁻⁴/day for storage at room temperature. The tomatoes stored at room temperature were subjected to analysis over 90 days of storage, period after which both the appearance and sensory characteristics of the product fell below the levels of consumer acceptability. As for the tomatoes stored at refrigeration temperature, the original sensory characteristics were maintained throughout the entire storage period of 180 days.     

Physical and sensory characteristics of processed Ras cheese spreads with formulated emulsifying salt mixtures

Processed cheese spreads were produced using Ras cheese and various emulsifying salt mixtures. Acidified Ras cheese (2 months old) was used as the cheese base and blended with following emulsifying salt mixtures: (i) Na‐pyrophosphate + Na‐polyphosphate, (ii) Na‐pyrophosphate + Na‐polyphosphate + Na‐tripolyphosphate, and (iii) Na‐pyrophosphate + Na‐polyphosphate + Na‐orthophosphate + Na‐tripolyphosphate. The control cheese spreads were also made with commercial emulsifying salts, Joha S10, S9s, and NO. Water activity, oil index, meltability, flow behavior, color parameters and sensory evaluations for the resultant processed cheese were studied. Cheeses showed slight differences in water activity while the differences were significant in oil index and meltability values. Shear stress of the processed cheese samples measured at 60°C was different from that of the control. It was dependent upon the individual salts in emulsifying mixture. Spreadable Ras cheese was shinier in treatment (iii) and exhibited darker color in samples stored at room temperature (20°C). Sensory evaluation showed that all cheeses were acceptable but the mixtures (i) 70:30, (ii) 60:30:10, and (iii) 50:20:20:10 produced the most acceptable processed cheese.