Dielectric spectroscopy-based characterisation of different types of Paneer (Indian cottage cheese) in terms of texture,microstructure and functional groups

Different variants of Paneer were prepared with cow milk (CM), buffalo milk (BM), skimmed milk powder (SMP) and blends (40:60, 50:50, 60:40) of SMP with CM/BM. The Paneer composition, texture, microstructure and spread of functional groups were correlated with the dielectric capacitance values. Results depicted a strong correlation (R² > 0.95) between milk used for Paneer making and its proximate composition in terms of the capacitance value, and it was highest for CM followed by BM; 100% SMP Paneer recorded lowest values. Paneer made from blends of SMP and liquid milk had the lowest transmittance value, indicating higher total protein content.     

脱脂乳热处理对农家干酪品质及其加工的影响

乳制品生产离不开热处理，用于加工的脱脂乳的品质和微生物数量对农家干酪的品质和生产中关键环节的控制都有重要的影响。针对脱脂原料乳经不同热处理后对乳中蛋白质，农家干酪的产率厦加工品质的影响进行了探讨。     

Microbiological quality of ayib, a traditional Ethiopian cottage cheese

One-hundred samples of ayib, a traditional Ethiopian cottage cheese, were purchased from Awassa market and analysed for their aerobic mesophilic counts, psychrotropic counts, yeasts and molds, coliforms, spore-formers, enterococci, lactic acid bacteria, Listeria monocytogenes, staphylococci and Bacillus cereus. The majority of the samples showed counts of mesophilic aerobic bacteria, yeasts and enterococci of 10⁸, 10⁷ and 10⁷ cfu/g. About 55% of the samples were positive for coliforms and faecal coliforms. Listeria spp. were not detected in any of the samples. B. cereus and S. aureus were isolated at varying frequencies but at low numbers (10²–10³). The pH value of the samples varied between 3.3 and 4.6 with about 40% having pH lower than 3.7.     

Short communication: Production of cottage cheese fortified with vitamin D

The availability of alternative food products fortified with vitamin D could help decrease the percentage of the population with vitamin D deficiency. The objective of this study was to fortify cheese with vitamin D. Cottage cheese was selected because its manufacture allows for the addition of vitamin D after the draining step without any loss of the vitamin in whey. Cream containing vitamin D (145 IU/g of cream) was mixed with the fresh cheese curds, resulting in a final concentration of 51 IU/g of cheese. Unfortified cottage cheese was used as a control. As expected, the cottage cheese was fortified without any loss of vitamin D in the cheese whey. The vitamin D added to cream was not affected by homogenization or pasteurization treatments. In cottage cheese, the vitamin D concentration remained stable during 3 weeks of storage at 4°C. Compared with the control cheese, the cheese fortified with vitamin D showed no effects of fortification on cheese characteristics or sensory properties. Cottage cheese could be a new source of vitamin D or an alternative to fortified drinking milk.     

Estimation of compaction and fouling effects during membrane processing of cottage cheese whey

Effects of transmembrane pressure on membrane performance and permeate flux were studied using pure water and cottage cheese whey. The transmembrane pressure was varied from 0·8 to 30 bar and the temperature was maintained at 21 ± 1°C. Mechanical deformation and compression of the ultrafiltration membrane used (MW cut-off 25 000 daltons) were considered to be the main factors responsible for the non-linearity of the relationship between processing pressure and water permeate flux rate. During membrane processing of cottage cheese whey, a further deviation from linearity was observed, possibly due to the effect of membrane fouling. Assuming that compaction effects were dependent only on the transmembrane pressure applied and not on the type of liquid being processed, compaction effects appeared to exceed fouling markedly in the pressure range 4–30 bar. Fouling and compaction effects were of the same order at pressures below 3 bar. In spite of the compaction phenomena, no substantial change in total solids flux was observed in membrane processing of cottage cheese whey.     

Cactus cladode polysaccharide as cryoprotectant in frozen Paneer (Indian Cottage Cheese)

The study investigated the optimisation of freezing conditions for Paneer (Indian cottage cheese) incorporated with cactus cladode polysaccharide as cryoprotectant. The freezing rate of both natural and commercial cryoprotectant‐containing samples varied significantly. The optimised (2% natural cryoprotectant) Paneer sample had about 44% moisture content, 14% protein, 16% carbohydrate and 22% fat. Freezing time of optimised Paneer sample packed in metalised polyester was 40 min. The study concluded that Paneer incorporated with 2% cactus cladode polysaccharide, packaged using metalised polyester and frozen with packaged immersion freezing method, had the least freezing time (40 min) and retained better texture during freezing.     

Assessment of the quality of cottage cheese produced from standard and protein-fortified skim milk

The effects of milk protein fortification on the texture and microstructure of cottage cheese curd were evaluated. Protein powder (92.6% protein) was added to the skim milk at a level of 0.4% (w/w) to produce curds. Control curds with no protein powder addition were also produced. These curds were analysed for differences in yield, total solids, curd size, texture and structure. It was found that the addition of protein powder contributed to a significant yield increase, which can be attributed to increased water retention, with better curd size distribution. Control curds were firmer than the fortified curds and the structure showed less open-pore structure as revealed by electron microscopy. However, the addition of dressing masked the textural differences, and a sensory panel was unable to distinguish between cheeses produced from fortified milk and controls.     

Effect of carrot on quality improvement of sweet syrupy cheese ball (Rasgulla)

To evaluate the effect of carrot on the quality improvement of the sweet syrupy cheese ball known as Rasgulla, six types of Rasgulla samples containing carrot paste in the proportions of 0, 10, 20, 30, 40 and 50% were prepared and stored in closed containers at 25°C for 40 h. With increasing storage time the acidity of syrup, free fatty acid formation, absorptivity value and colour of all Rasgulla samples increased. The addition of carrot to chhana (analogous to cottage cheese) decreased acid and free fatty acid formation in Rasgulla syrup, decreased absorptivity, and also gave colour stability. Carrot concentration up to 30% improves the quality of Rasgulla. More than a 30% concentration of carrot reduced the oxidative stability of Rasgulla, while a more than 40% carrot concentration reduced its colour stability. Thus, the use of carrot up a concentration of 30% is suggested to increase the oxidative stability as well as the colour stability of Rasgulla.     

Production of probiotic cheese (cheddar-like cheese) using enriched cream fermented by Bifidobacterium infantis.

Probiotic cheeses (Cheddar-like cheese) were produced with microfiltered milk standardized with cream enriched with native phosphocaseinate retentate and fermented by Bifidobacterium infantis. During the manufacture and storage of cheeses, viability of the bifidobacteria was determined. Biochemical changes such as proteolysis, sugar metabolism, and organic acids production were estimated. No bifidobacteria growth was observed during cheese-making steps. Bifidobacteria survived very well in cheeses packed in vacuum sealed bags kept at 4 degrees C for 84 d and remained above 3 x 10(6) cfu/g of cheese. No significant difference was observed between cheeses produced with or without bifidobacteria for fat, protein, moisture, salt, ash, or pH. After 12 wk of storage, more than 56% of the as1-CN was hydrolyzed in cheeses that were produced with bifidobacteria and inoculated at 10(8) cfu/g in the cream, and > 45% of hydrolysis was observed in the control cheese. However, no significant differences in the electrophoretic sodium dodecyl sulfate-PAGE patterns were observed in cheeses at any period of storage. At the first day after manufacture, lactose was completely hydrolyzed in cheeses made with bifidobacteria, which suggested high beta-galactosidase activity by B. infantis. Small quantities of acetic acid were detected in bifidus cheeses. The results indicated that B. infantis introduced into hard pressed cheese exhibited excellent viability during storage for 12 wk and could be metabolically active.     

Electron microscopy of normal and defective cottage cheese curd

Defects in cottage cheese curd were examined by electron microscopy and the structure of defective curd was compared with that of normal curd at cutting. The formation of the minor sludge frequently found as a thin layer at the bottom of vats was attributed to the very low _pH produced by the sedimentation of agglutinated starter bacteria. In contrast, the ultrastructural appearance of curd from incidents of major sludging, in which whole vats were lost, suggested that a slowing down of acid production had caused the defect by allowing aggregated micelles to sediment. It is suggested that in such cases loss of acid production is the result of starter destruction by low initial numbers of bacteriophages.     

Potential applications of high pressure for improvement in salmon quality

Cold-smoked salmon is an important value added, ready-to-eat food. Quality issues associated with cold-smoked salmon are examined. Effects of smoking, drying, enzymatic spoilage, feed usage, textural and biochemical changes during frozen storage of cold-smoked salmon are described. Important pathogens associated with cold-smoked salmon, such as Listeria monocytogenes and other spoilage organisms are also described and potential areas for further research are identified. Recent advances in the application of high pressure processing to seafood safety and quality improvement are discussed and the potential of this technology to improve the quality of cold-smoked fish from farmed Atlantic salmon is outlined.     

Evolution of quality parameters of high pressure processing (HPP) pretreated albacore (Thunnus alalunga) during long-term frozen storage

The aim of this work was to study the application of high pressure processing (HPP) before freezing for maintaining as much as possible the fresh characteristics of albacore steaks after long-term storage. HPP treatments were applied at 200 MPa for 0–6 min. Then, samples were immediately frozen (−20 °C) and stored (−20 °C) for up to 12 months. Once thawed (4 °C; 24 h), weight losses, color, texture, lipid oxidation (TBARS) and salt-soluble protein content were analyzed.After 12 months of frozen storage, 200 MPa for 6 min minimized thawing loss inherent to freezing and frozen storage and decreased TBARS (53.9%) with respect to the control. However, it resulted in changes in color (higher L*, b* and ΔE values) and texture (higher adhesiveness and springiness) and decreased the salt-soluble protein content with respect to non-pretreated samples. Nevertheless, after cooking, there were no differences in color and texture between HPP pretreated fish and the controls.     

Electrophoresis of cottage cheese whey proteins and their polymers.

Cottage cheese whey solutions containing sodium dodecyl sulfate were resolved electrophoretically on 5% sodium dodecyl sulfate polyacrylamide gels. Major bands were identified by comparing their electrophoretic mobilities to those of known whey components. Other components were identified principally from molecular weights determined from a calibration correlating mobility and molecular weight. Conditions which affect polymerization of proteins were studied in whey and solutions of purified beta-lactoglobulin. Formation of a number of polymers was induced by concentrating the whey samples, lowering the temperature, adjusting pH, or adding salts. The dimer, trimer, tetramer, and octamer of beta-lactoglobulin, the dimer and trimer of bovine serum albumin, and several unidentified components in the 100,000 to 300,000 molecular weight range were observed. The octamer state of beta-lactoglobulin was observed in whey at pH values between 5.1 and 8.0, at temperatures below 10 C, and with .2M addition of potassium thiocyanate, potassium iodide, calcium chloride, or sodium acetate. Similar polymer formation, and temperature and pH effects, were observed with solutions of purified beta-lactoglobulin, which contained dimers, trimers, and tetramers. The beta-lactoglobulin octamer in whey samples could be dissociated by the addition of acid. The bovine serum albumin dimer appeared in whey at pH above 6.2 and at -minus 1 C.     

乳扇加工新工艺及品质的研究

在乳扇传统加工工艺基础上,结合意大利干酪加工技术,研究乳扇新加工工艺和产品质量。筛选的最佳工艺为:生鲜乳→质检→净乳→巴氏杀菌→冷却→接种发酵→加酶凝乳→凝乳、切割→乳清成熟→堆叠后熟→热烫拉伸→成型→干燥→包装→检验→成品。水牛奶乳扇的蛋白质平均质量分数29.25%,脂肪平均质量分数为51.14%,水分10.14%;霉菌≤50g-1,酵母菌≤50g-1,大肠菌群(最近似值)≤0.30 g-1,致病菌未检出。产品质量符合相关规定。     

High pressure processing (HPP) of honey for the improvement of nutritional value

The present study was undertaken to assess the effect of high pressure processing (HPP) on total phenolic content (TPC) in manuka honey. Manuka honey is known for its amazing antimicrobial action and antioxidant properties. The effect of HPP (200, 400 and 600 MPa) at ambient and moderate temperatures (53.41 ± 0.30 °C, 65.29 ± 1.77 °C, 71.92 ± 1.63 °C) and their combination for different processing time (5, 10 and 15 min) was investigated. Conventional thermal processing (51.74 ± 0.03 °C, 61.90 ± 0.10 °C and 71.58 ± 0.04 °C) was also carried out as comparison to HPP. Operating HPP at 600 MPa (26.80 ± 0.95 °C–30.18 ± 2.14 °C) for 10 min was found to be the most effective process with 47.16% increment in TPC as compared to unprocessed honey, whereas no significant increase (p < 0.05) was observed in thermal processing as well as in combined HPP–thermal processing. Therefore, HPP at ambient temperatures could be an appropriate method to produce tastier and more nutritive manuka honey.Industrial relevanceThe preservation of total phenolic content (TPC) as a main phytochemical component in honey is very important with direct impact on nutritional value and antioxidant activity. A significant increase in the TPC was obtained by processing. Results demonstrated the HPP capability to increase TPC in manuka honey by 47%. From a nutritional perspective, this result is associated with the production of a higher antioxidant honey, known to prevent certain diseases such as cancer. The study generates a new approach in honey processing which can guarantee the high nutritional quality of honey and its original natural freshness.     

Effect of high pressure processing on the quality of squid (Todarodes pacificus) during refrigerated storage

The influence of high pressure processing (HPP) on the inhibition of trimethylamine-N-oxide demethylase (TMAOase) activity and off-odour production in squid treated at 300 MPa for 20 min was investigated during 12 days of refrigerated storage. TMAOase activity of raw squid (21.5 nkat/g) was significantly decreased to approximately 5 nkat/g after 20 min of HPP. The production of dimethylamine (DMA) in HPP-treated squid for 20 min was significantly decreased to 0.31 μmol/g after 12 days of storage. The decrease in DMA was correlated with the decrease in TMAOase activity. At 300 MPa, the number of total aerobic bacteria in squid was reduced by 1.26 log units after 20 min of HPP. The HPP-treated samples effectively reduced the amount of trimethylamine (TMA). Therefore, the HPP could be used as a promising alternative technology to retard the quality deterioration of squid by inhibiting TMAOase activity and microbial growth.     

Characterization of cottage cheese using Weissella cibaria D30: Physicochemical,antioxidant, and antilisterial properties

This study aimed to evaluate the potential of Weissella cibaria D30 as an adjunct culture in cottage cheese, including an assessment of antioxidant, antilisterial, and compositional parameters. Cottage cheese samples were manufactured using a commercial starter culture and probiotic strains Lactobacillus rhamnosus GG (GG) or W. cibaria D30 (W) and without probiotic (control). Samples were stored at 4 ± 1°C for 28 d. Bacterial cell counts (log cfu/g) of control, GG, and W samples were counted at 0, 7, 14, 21, and 28 d. Counts of W. cibaria D30 in the W samples remained at 6.85 log cfu/g after 28 d. Total solids, fat, protein, ash, and pH were measured and no significant differences were observed in compositional parameters or pH after 28 d of storage in all cheeses except those inoculated to Listeria monocytogenes. To measure the antilisterial effect, Listeria monocytogenes was inoculated into the cottage cheese samples and bacterial cell counts were obtained at 0, 6, 12, 24, 48, 72, 96, 120, and 144 h. Listeria monocytogenes counts were less than the analytical limit of detection (<10 cfu/g) in the inoculated GG and W samples, whereas the counts of L. monocytogenes in the inoculated control sample remained at 3.0 log cfu/g after 144 h. We used the DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS [2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] radical scavenging activity assays to assess antioxidant activity: GG and W samples exhibited significant increases in antioxidant activity compared with the control sample. These results indicate that W. cibaria D30 has potential as an adjunct culture in the dairy industry.     

Effect of high pressure on fresh cheese shelf-life

The effect of high pressure (HP; 300 and 400 MPa for 5 min at 6 °C) on physico-chemical, microbial, color, texture and sensorial characteristics of starter-free fresh cheeses stored at 4 and 8 °C was studied. Physico-chemical parameters considered were total solids, fat, total protein, pH, whey loss and water activity. The microbiological quality was studied, on cheeses stored at 4 and 8 °C, by enumerating aerobic mesophilic bacteria, lactococci, psychrotrophic bacteria, Enterobacteriaceae, Escherichia coli, molds and yeasts. Cheeses treated at 300 and 400 MPa, stored at 4 °C, presented a shelf-life of 14 and 21 days, respectively, compared to untreated control cheese, which presented a shelf life of 7 days. On the other hand, HP treatments modified the texture (more firm) and color (more yellow) compared to control cheeses. These changes were detected by instrumental and sensory analysis.