Skim Milk Powder Research Articles

Non-Fat Yogurt Fortified with Whey Protein Isolate: Physicochemical, Rheological, and Microstructural Properties.

The demand for low- and non-fat products has recently increased due to the health problems, such as obesity, diabetes, and cardiovascular diseases, that have resulted from high-fat products. However, the reduction in fat can affect the quality of products adversely. The objective of this work was to explore the potential of whey protein isolate (WPI) in improving the quality of non-fat yogurt prepared using skim milk powder (SMP). Yogurt mixes (standardized at 14% total solids) were formulated using SMP as a milk base enriched with WPI. The SMP was replaced by WPI in the yogurt mixes at a rate of 3, 5, 7, and 9%. Full-fat and non-fat set-style yogurts were prepared from whole milk and skim milk, respectively, as controls. Yogurts were fermented at 43 °C to get a pH of 4.6 and stored at 4 °C for the next day. The texture, microstructure, rheological characteristics, and sensory properties of the yogurt samples were studied. The incorporation of WPI increased the water holding capacity to 50% as compared to the non-fat control. This improved the rheological properties while the yogurt viscosity increased in direct proportion with increasing the WPI. The firmness of yogurt was inversely proportional to the increase in WPI, which resulted in 180 g firmness when 9% WPI was added to the non-fat yogurt formulations. Yogurts’ microstructure improved by the addition of WPI. The non-fat yogurt incorporated with 3 and 7% WPI had comparable sensory and textural characteristics to the full-fat yogurt. WPI can be used as a fat replacer to develop low-fat yogurt with desired features. WPI may be a natural and economical ingredient for producing low- and non-fat fermented dairy food products.

Effect of substituting whey cream for sweet cream on the textural and rheological properties of cream cheese

In the manufacture of cream cheese, sweet cream and milk are blended to prepare the cream cheese mix, although other ingredients such as condensed skim milk and skim milk powder may also be included. Whey cream (WC) is an underutilized fat source, which has smaller fat droplets and slightly different chemical composition than sweet cream. This study investigated the rheological and textural properties of cream cheeses manufactured by substituting sweet cream with various levels of WC. Three different cream cheese mixes were prepared: control mix (CC; 0% WC), cream cheese mixes containing 25% WC (25WC; i.e., 75% sweet cream), and cream cheese mixes with 75% WC (75WC; i.e., 25% sweet cream). The CC, 25WC, and 75WC mixes were then used to manufacture cream cheeses. We also studied the effect of WC on the initial step in cream cheese manufacture (i.e., the acid gelation process monitored using dynamic small amplitude rheology). Acid gels were also prepared with added denatured whey proteins or membrane proteins/phospholipids (PL) to evaluate how these components affected gel properties. The rheological, textural, and sensory properties of cream cheeses were also measured. The WC samples had significantly higher levels of PL and insoluble protein compared with sweet cream. An increase in the level of WC reduced the rate of acid gel development, similar to the effect of whey phospholipid concentrate added to mixes. In cream cheese, an increase in the level of added WC resulted in significantly lower storage modulus values at temperatures <20°C. Texture results, obtained from instrumental and sensory analyses, showed that high level of WC resulted in significantly lower firmness or hardness values and higher stickiness compared with cream cheeses made with 25WC or CC cream cheeses. The softer, less elastic gels or cheeses resulting from the use of high levels of WC are likely due to the presence of components such as PL and proteins from the native milk fat globule membrane. The use of low levels of WC in cream cheese did not alter the texture, whereas high levels of WC could be used if manufacturers want to produce more spreadable products.

Assessment of market milk adulteration in Tiruchirapalli city of Tamil Nadu

A study was conducted to analyze the market milk samples sold in Tiruchirapalli city of Tamil Nadu for the presence of adulterants. A total of 110 milk samples, 10 from the organized brands, 50 from local vendors and 50 from tea and coffee shops were collected. The present study revealed the presence of starch in 02 milk samples (1.82%) and that to from organized brands were detected. Further, the presence of neutralizers, detergents and sodium chloride were found in 36 samples (32.73%), 21 milk samples (19.09%) and 33 milk samples (30%) respectively. The skimmed milk powder was detected in all the ten organized brands. The milk samples obtained from local vendors, tea and coffee shop were negative for skimmed milk powder. The study also revealed the presence of sugar in 45 milk samples (40.91%), hydrogen peroxide in 03 samples (2.73%) and pond water/nitrate in 20 milk samples (18.18%) respectively. In addition, the study revealed that none of the sample was found positive for the presence of alizarin, formalin, urea, glucose / dextrose, cellulose, maltodextrin, protein and boric acid.

Optimization and Development of Ready to Eat Chocolate Coated Roasted Flaked Rice as Instant Breakfast Food.

The present study aimed to optimize and develop ready-to-eat rice-based functional breakfast food using response surface methodology. The levels of ingredients viz. skim milk powder, guar gum, and ferrous sulfate were pre-optimized and remained constant, whereas jaggery and dark chocolate were taken as independent variables. The optimum levels of jaggery and dark chocolate for chocolate-coated roasted flaked rice (CCRFR) were 8.49 g and 25.43 g, respectively. The physical, pasting, textural, functional, morphological, optical, and sensory characteristics of CCRFR and uncoated roasted flaked rice (RFR) were also studied. CCRFR had significantly higher mineral (iron and calcium) and total polyphenolic contents. Furthermore, the dimensional, sensory, and functional properties were also improved. The changes in morphological structure were also observed between the CCRFR and uncoated product using scanning electron microscopy. The coating adds nutritional value to the roasted rice and renders it an essential functional RTE convenience gluten-free cereal breakfast item.

Improving acid resistance and characteristics of microencapsulated Lactobacillus brevis RK03 using top fluid bed drying technology

Thermoprotective carrier agents increase bacterial viability during the drying process. We investigated the ability of various carriers, including skim milk powder, casein, and whey protein, to improve the survival rate of Lactobacillus brevis RK03 under gastrointestinal tract conditions. Employing optimized top fluid bed drying (TFBD) conditions (40 min at 50 °C), the highest bacterial survival rate (95 %) was achieved using casein and whey protein as carriers for RK03. Additionally, whey protein-microencapsulated RK03 displayed the highest survival rates in gastric juice at pH 3.0 (96 %) and 2.0 (75 %). Further, whey protein-microencapsulated RK03 exhibited better dispersibility and solubility than RK03 microencapsulated with other carriers, displayed a slower degradation rate at 50 °C and 60 °C, and had the lowest activation energy (30.27 J/mol). These results indicate that the use of whey protein as a carrier during TFBD is suitable for the production of RK03 probiotic powder.

Ultrasound-modified interfacial properties and crystallization behavior of aerated emulsions fabricated with pH-shifting treated pea protein

The interfacial properties of pea protein isolate (NPP) were modified by pH12-shifting (BPP) and ultrasound treatment as a substitute for skimmed milk powder (SMP) in ice cream. The physicochemical properties and fat crystallization in emulsions before and after whipping were analyzed. Compared with SMP, the BPP emulsion displayed superior stability with small particle size and high viscosity. Fat clusters were observed in both SMP and BPP emulsions, which may promote the puncture and protrusion of fat crystals within droplets and lead to partial coalescence to allow air bubble entrapment. Aeration activity of BPP in cream was 1.5-fold that of NPP. Although the overrun value was smaller than SMP cream, the BPP cream retained the stable shape and had a slow melting rate due to its interactive dimensional network of fat. Ultrasound treatment was found to promote fat crystallization of emulsions, leading to the improved stability of final products.

Fluidized-Bed Granulation of Probiotics-Encapsulated Spray-Dried Skim Milk Powder: Effects of a Fluidizing Aid, Moisture-Activation and Dehydration.

A probiotic powder of poor flowability with high dust content, prepared by spray drying reconstituted skim milk fermented with Lactobacillus rhamnosus GG (LGG), was granulated by fluidized-bed granulation (FBG). The effects of the addition of skim milk powder (SMP) as a fluidizing aid, and of simple moisture-activation with or without dehydration, were investigated with respect to the performance of the FBG process. A fine, poorly fluidizable LGG powder (Geldart Group C) could be fluidized and granulated, with a 4- to 5-fold increase in particle size (d4,3 = 96–141 μm), by mixing with SMP (30–50%), which has larger, fluidizable particles belonging to Geldart Group A. Moisture-activation after the mixing, followed by fluidized-bed dehydration with hot air to remove excess moisture, further improved the FBG; the yield of the granules increased from 42% to 61% and the particle size distribution became much narrower, although the average particle size remained almost the same (d4,3 = 142 μm). These granules showed a popcorn-type structure in scanning electron microscopy images and encapsulated a sufficient level of viable LGG cells (1.6 × 108 CFU g−1). These granules also exhibited much better flowability and dispersibility than the spray-dried LGG powder.

Optimization of the freeze-drying of marine yeast Sporidiobolus pararoseus ZMY-1 for its application in biocontrol of fungal infections

Penicillium expansum, Botrytis cinerea and Alternaria alternata are three common fungal pathogens infecting a variety of fruit and vegetables, resulting in postharvest decay and huge loss. In this work, the marine yeast Sporidiobolus pararoseus ZMY-1 was studied for its antagonistic effect against P. expansum, B. cinerea and A. alternata both in vitro and in vivo. The results showed that S. pararoseus ZMY-1 antagonized the three pathogens both in vitro and in apple fruit, and the antagonistic effect against P. expansum was the best. Considering commercializing S. pararoseus ZMY-1 as a potential biocontrol agent, three protective agents (skim milk powder, polyethylene glycol and trehalose) were added to make freeze-dried S. pararoseus ZMY-1. The appropriate cryoprotectant combination was optimized by a three-factor and three-level orthogonal experiment, which consisted of 1.5% skim milk powder, 0.1875% polyethylene glycol and 5.25% trehalose, and the survival of freeze-dried S. pararoseus ZMY-1 was improved to 93.9%. The freeze-dried yeast also showed good biocontrol efficacy against P. expansum, B. cinerea and A. alternata in apple fruit. Refrigerated storage at 4 °C was better than storage at 20 °C to maintain the stability of freeze-dried yeast, with higher survival of 66.5% after storage for 3 months. Therefore, freeze-dried marine yeast S. pararoseus ZMY-1 has good potential for biocontrol applications for postharvest fruit.

Ovine ice cream made with addition of whey protein concentrates of ovine-caprine origin

The use of whey protein concentrates (WPC) of ovine/caprine origin in the manufacture of ovine ice cream (5% fat) was evaluated. Three ice cream mixes were prepared using ovine skimmed milk and cream, stabilisers/emulsifiers, mix of sucrose:fructose (50:50) and bovine skimmed milk powder (SMP) (35% protein; ice cream A), WPC 65% protein (ice cream B) or WPC 80% protein (ice cream C). Ice cream A melted faster than ice creams B and C, and presented higher overrun (76%), compared with ice cream B (46%) and ice cream C (36%); for hardness the opposite was true. Ice cream A was significantly brighter, ice creams B and C were more yellow. The flavour scores of ice cream B was similar to those of ice cream A. The substitution of bovine SMP with ovine/caprine WPC (65% protein) in ovine ice cream to produce a product with no ingredient of bovine origin seems to be feasible.

Quality of Set Yogurts Made from Raw Milk and Processed Milk Supplemented with Enriched Milk Fat Globule Membrane in a Two-Stage Homogenization Process.

Dairy products are relevant in the food industries as functional ingredients for several food products and contribute towards human nutrition in ameliorating certain disorders. In this study, set yogurts were produced from raw milk and processed milk combined with 4% Lacprodan®PL20 concentration and subjected to two-stage pressure homogenization. The total solids concentration of the mixture was raised to 15% using SMP (skim milk powder). The purpose of this study was to investigate the effect of Lacprodan®PL20 on the set yogurt quality produced by homogenization-induced pressure and its interaction with milk components. The changes in the physical and chemical attributes of the milk fat globule membrane (MFGM) via destabilization of the membrane significantly affected the physicochemical properties of set yogurts produced from processed or raw milk. There was a slight variation in MFGM-specific proteins detected in the set yogurts. Set yogurt produced from homogenized raw milk (HRM) had a considerably higher water-holding capacity, firmness, and apparent viscosity. The microstructure of HRM was dense and compacted, unlike non-homogenized raw milk (NRM) with large MFGM fragments and pore holes between the matrixes. The inclusion of homogenization showed a remarkable improvement in set yogurt quality, promoting interaction between MFGM components and milk proteins.

Tracking the dissolution behavior of zinc oxide nanoparticles in skimmed milk powder solutions

Zinc oxide nanoparticles (ZnO NPs) are recently recommended as food additives owing to their outstanding nutritive function. Therefore, understanding their comprehensive information and stability in food samples is highly necessitated. However, the characterization of ZnO NPs in the complex food matrices remains a great challenge, limiting an in-depth understanding of their transformation during food storage. In this study, the hollow fiber flow field-flow fractionation was combined with UV–Vis absorption spectroscopy and inductively coupled plasma optical emission spectroscopy to assess the dissolution behaviors of ZnO NPs in skimmed milk powder solutions by monitoring the changes in the residual ZnO NPs and the amount of dissolved Zn(II) ions. The simultaneous characterization of these two Zn species in skimmed milk powder solutions was achieved without the need for tedious sample pretreatments, and the dissolution of ZnO NPs in skimmed milk powder solutions had time- and temperature-dependent behaviors.

Shelf life of Microencapsulated and Free Cells of Lactobacillus plantarum IS-10506 at Different Temperatures

Survival of microencapsulated probiotic Lactobacillus plantarum IS-10506 ofdadih origin at different storage conditions has been investigated. L. plantarum cells suspension was dispersed in Flocel pH 101 mixed with skim milk powder and dried by Fluid Bed Dryer (FBD) at 37°C for 2 hours, then microencapsulated by 4.75% (w/v) sodium alginate and 5.5% (w/v) calcium chloride. The microencapsulated and free cells probiotics were packed in standing aluminium pouch and stored at three different temperatures, 24°C (room temperature), 4°C (chiller), and-20°C (freezer) for 24 weeks, and the viable counts of probiotic were enumerated using MRS Agar medium every two weeks. Microencapsulated and free cells of probiotic Lactobacillus plantarum IS-10506 showed stable viability at -20°C for 24 weeks. At 4°C free cells showed significant decreased of viability while microencapsulated cells showed stable viability at week 24. Storage at 24°C led to significant loss of viability (p< 0.05) of both free cells and microencapsulated cells after 8 and 10 weeks, respectively, to undetectable level. Moisture content in both of free cells and microencapsulated cells at 24° C significantly increased at week 2. While at 4°C, there was significant increase of moisture content observed in free cells at week 2, and microencapsulated cells showed significant increase of moisture content at week 10. Likewise, at -20°C, moisture content of both free and microencapsulated cells showed significant increase at week 2 and 10, respectively.

Safety and quality aspects of whole and skimmed milk powders.

Nowadays, dried milk products are highly traded and consumed all over the world, so we aimed in this study to evaluate to what extent whole and skim milk powders are safe and comply with Egyptian standards. Eighty samples of dried milk (50 whole milk powder and 30 skim milk powder) were gathered from several retailers and supermarkets for evaluation of their differing quality and safety parameters. The most frequent off-flavors recovered from whole milk powder samples were cooked ones and, in the case of skim milk powder samples, flat ones. Five samples of whole milk powder were of fair quality and three samples of poor quality, according to the sensory evaluation. The compositional parameters, moisture, %, fat, %, protein, %, and acidity, %, were measured as mean values of 3.90 ±0.15, 26.90 ±0.19, 25.53 ±0.27, and 0.99 ±0.03% in the examined whole milk powder samples and 3.77 ±0.08, 1.11 ±0.05, 34.62 ±0.29, and 1.22 ±0.03% in the examined skimmed milk powder samples, respectively. These results were within the range of component requirements set by the Egyptian Standard (2014; ES: 1780/2014) for dried milk products. Also, the microbiological safety of the milk powder samples was analyzed by assessment of the total viable count, total yeast and mold count, Coliforms count, Enterobacteriaceae, E. coli, C. sakazakii, Staphylococcus aureus, Salmonella, and Listeria monocytogenes. Staphylococcus aureus was the most prevalent isolate (36.00% and 6.67%) followed by Enterobacteriaceae (20.00% and 3.33%), of whole and skim milk powder, respectively. Enterobacteriaceae isolates included Enterobacter cloacae ssp. Cloacae, and Pantoea spp., which were specified by traditional biochemical tests and Vitek2 system. All Enterobacteriaceae isolated spp. were resistant to cephalothin, neomycin, tobramycin and colistin sulphate, and sensitive to chloramphenicol, gentamycin and nalidixic acid. E. coli, C. sakazakii, Salmonella, and Listeria monocytogenes couldn't be isolated from all the tested samples. By using Inductive Coupled Plasma - Mass Spectrometer (ICP-MS), we could measure lead and mercury as mean values of 0.243 ±0.069 and 0.261 ±0.052 mg/kg for whole milk powder samples at a percentage of 68.00 and 34.00%, while for the skim milk powder samples they were 0.150 ±0.037, and 0.347 ±0.110 mg/kg at a percentage of 66.67 and 40.00%, respectively. Finally, thirty-four whole milk powder and twelve skimmed milk powder samples didn't comply with Egyptian standards, so it is necessary for authorities to put more attention on this and regular monitor it.

Safety and quality aspects of whole and skimmed milk powders [pdf

Safety and quality aspects of whole and skimmed milk powders [pdf

Повышение эффективности выращивания телят в послемолочный период

Aim. To establish the effect of raising young cattle on whole milk, a substitute for whole and skimmed milk powder on its productivity and physiological state in the post-dairy period. Materials and Methods. The studies were conducted on three groups of young cattle of the first phase of cultivation, 10 heads each, at the age of 115 days with an initial live weight of 125.3-127.5 kg. Animals of all groups were given the same diet. During the dairy period, the calves of the control group received milk, a second and third substitute for whole milk and a substitute for skimmed milk powder. Classical and modern zootechnical, biochemical and mathematical methods of analysis were used in research. The digital material obtained in the course of the research was processed by the method of variation statistics, taking into account the Student's criterion of reliability and using the Microsoft Excel software package. Results. Taking into account the feed consumption in the scientific and economic experience showed that the consumption of silage-haylage mixture increased by 0.5-0.6 kg in the animals of the experimental groups. 1 kg of dry matter contained 10.47-10.56 MJ of exchange energy and 0.90-0.91 feed units, 13.4% of crude protein and 22.4-23.2% of fiber. Per 1 feed unit, 95.7-96.4 g of digestible protein was accounted for. As a result of the research, it was found that the majority of the blood parameters studied by us, reflecting the general physiological state of the body, in the compared groups were within the physiological norm. In the blood of animals of the II and III experimental groups, compared with control animals, there was an increase in the number of red blood cells by 10.0 and 9.8%, hemoglobin – by 5.8 and 3.9%, glucose – by 11.0 and 9.5%. The study of the growth dynamics of experimental animals during the experimental period of scientific and economic experience showed that the increase in the live weight of young animals of the experimental group was more intense than the control ones. At the same time, the average daily increase in live weight of control calves was 796.7 g, experimental calves-870.0 and 881.7 g, or increased by 9.2 and 10.7%. The increase in the growth energy of the bulls of the experimental group allowed to obtain an additional 4.4 and 5.1 kg of live weight per head during the experiment period. Based on the conducted studies, it was found that the cost of feed per kg of growth in the II and III experimental groups was lower than the control variant by 5.8 and 7.6%, and therefore the cost of growth in the experimental groups decreased by 6.1 and 7.7% compared to the control analogues, this allowed us to get additional profit per 1 head in the experimental groups in the amount of 8.35 and 10.58 rubles for the research period. Conclusion. The use of ZTSM and ZSOM in feeding young cattle at the age of 10-115 days provided an increase in the average daily increase in the post – dairy period by 9.2 and 10.7%, while reducing the cost of feed for obtaining an increase by 5.8 and 7.6%, the cost of growth-by 6.1 and 7.7 percent.

Foaming and foam mat drying characteristics of ripe banana [Musa balbisiana (BB)] pulp

AbstractFoam‐mat drying characteristics of wild ripe banana [Musa balbisiana (BB)] pulp on the attributes of the product were investigated. The effects of pulp concentration (PC), skim milk powder (SMP) and whipping time (WT) on foaming characteristics such as foam density, drainage volume and foam expansion were studied. The obtained optimum condition for the foaming process was 9.62°Brix of PC, 8.18% of SMP, and 145.54 s of WT. The hot air drying of banana foam was carried out at 50–70°C; the drying rate and moisture diffusivity (3.9–5.9 × 10−10 m2/s) increased with drying temperature. The physico‐chemical properties of banana foam powder such as moisture content, water activity, bulk density, and Carr index decreased with an increase in drying temperature, whereas hygroscopicity, water solubility index, and water absorption index increased. The dried samples were moderately bright in color and had a porous microstructure. The present study is expected to be useful in the preparation of banana powder.Practical ApplicationsFoam‐mat drying technology is a pragmatic method to dry fruit juices and pulps. The concept behind the foam‐mat drying is an increase in the surface area of material to be dried. The process depends on the material property of pulp/juice and the use of the additives to create a foam structure and ensuring its stability during the phase of drying to offer granular products having low bulk density.

Development of instant phirni mix (a traditional dairy dessert) from high amylose rice, skim milk powder and carboxymethyl cellulose-resistant starch, predicted glycemic index and stability during storage

High amylose rice (HAR) and carboxymethyl cellulose (CMC) are ideal choices to enhance the resistant starch and reduce the glycemic index of dairy desserts. Therefore, the effect of ingredient composition (i.e., skim milk powder: high amylose rice flour -SMP: HAR, and carboxymethyl cellulose- CMC) on physical characteristics of phirni dry mix were investigated in the present study. Variation in SMP: HAR flour and CMC concentration significantly (p < 0.05) affected the insolubility index, wettability, Hausner ratio, luminosity (L*), and yellowness (b*) of different phirni dry mix samples. Design expert predicted SMP (70%), HAR (30%) and CMC concentration of 0.85% as desirable conditions for preparation of phirni dry mix. A typical A-type diffraction pattern and absorption bands representative of proteins, lactose and starch were detected in optimized phirni dry-mix (OPDM). Irrespective of packaging material and storage condition, resistant starch (RS) increased significantly (p < 0.05) while predicted glycemic index (pGI) showed significant (p < 0.05) decrease during storage. However, maximum RS content (7.57%) and minimum pGI (44.95) were recorded in LDPE packed samples (LDPE-PS) on 90th day of storage under accelerated conditions. At the same time, moisture content, water activity, free fatty acids, and peroxide value increased significantly (p < 0.05), while overall acceptability showed a significant (p < 0.05) decrease in LDPE-PS. The inference drawn from the present study was that irrespective of packaging material and storage condition, the OPDM was safe to consume up to 90 days, however, aluminum laminated package and ambient storage condition could be better options to retain the quality of OPDM with better consumer acceptability.

Performance of Holstein calves receiving increased nutrient intake through the addition of skim milk or milk replacer powder to the whole milk

The purpose of this research was to describe the performance of Holstein calves before and after weaning when total solids in their daily milk were increased with skim milk or milk replacer powder. Forty-five female Holstein calves (body weight = 39.5 ± 1.61 kg) were assigned in random to 1 of 3 treatments: 1) whole milk (WM) with total solids of 123 ± 4.1 g/kg, 2) whole milk + skim milk powder (WM + SM) with total solids of 181 ± 6.2 g/kg, and 3) whole milk + milk replacer powder (WM + MR) with total solids of 184 ± 9.7 g/kg. Calves received 6 l/day of milk from days 2–14, 7 l/day from days 15–35, 6 l/day from days 36–42, 5 l/day from days 43–49, and then 2 l/day from days 50 until weaning (d 56). Calves remained in the study until day 90. Calves exhibited no difference in their pre- and post-weaning starter consumption. Although pre-weaning feed conversion efficiency was slightly different among calves, post-weaned calves receiving WM were more efficient in converting feed nutrients to body weight gain. Evolution of body frame development was slightly different among calves. However, WM + SM-fed calves had greater body length at weaning. Pre-weaning weight gain and body weight at weaning were greater when calves consumed high-solids milk based on SM or MR. Feeding WM + SM increased the number of days with diarrhea, which resulted in the highest proportion of calves in this group to receive antibiotics treatment. Amount of electrolytes administered per calf as well as days with antibiotic therapy were generally lesser in WM-fed calves. Slight treatment differences were noted in post-weaning total-tract digestion of DM, CP and OM in calf starter. However, fat digestibility was greatest in calves consuming WM + SM. Overall, our findings indicate that a high-solids milk feeding strategy based on SM or MR improved calf growth rate in the pre-weaning phase while having no effect on starter consumption. However, diarrhea incidence increased when calf nutrient intake was increased through SM.

Influence of drying conditions, food composition, and water activity on the thermal resistance of Salmonella enterica

Salmonella contamination of low-water activity (aw) foods poses a serious concern worldwide. The present study was conducted to assess the effects of drying conditions, food composition, and water activity on the desiccation tolerance and thermal resistance of S. Enteritidis FUA1946, S. Senftenberg ATCC43845 and S. Typhimurium ATCC13311 in pet food, binder formulation, and skim milk powder. The samples were wet inoculated with the individual Salmonella strains and were equilibrated to aw 0.33 and 0.75, followed by an isothermal treatment at 70 °C. The thermal inactivation data was fitted to the Weibull model. Irrespective of the aw, food composition and physical structure of the selected foods, strain S. Enteritidis FUA1946 displayed the highest desiccation and thermal resistance, followed by S. Senftenberg ATCC43845 and S. Typhimurium ATCC13311. The food matrix and strain type significantly (p < 0.05) influenced the thermal resistance of microorganisms in foods along with aw change during thermal treatments. To further study the effect of food composition, an additional set of experiments using dry inoculation of the resistant Salmonella strain in the low-aw foods was designed. Significant (p < 0.05) matrix-dependent interaction on Salmonella reduction was observed. The water adsorption isotherms of selected low-aw foods were measured at 20 and 70 °C to relate the thermal inactivation kinetics with the change in the aw. The characterization of thermal resistance of the Salmonella serovars in low-aw products with different compositions and aw in this study may be used for the validation of thermal challenge studies.

Assessment of powder flow, functional and microbiological characteristics of ozone-treated skim milk powder

The influence of ozone treatment (OT) of skim milk powder (SMP) on functional, physicochemical characteristics, powder flow behaviours and microbiological quality was evaluated. SMP was ozone-treated for 0 (control), 30, 60, 90 or 120 min. Particle size parameters of samples were not affected by OT. OT increased dispersibility and foaming capacity, but decreased wettability time. The cohesion index of samples ranged from 11.98 to 18.34, with higher treatment times decreasing it. OT significantly decreased the tendency for caking and cohesion, as well as compaction characteristics, and increased the flow stability of ozone-treated samples compared with control. OT could be effective for improving SMP flow behaviours in terms of caking, cohesion, and compaction. OT for 120 min decreased the count of all analysed microorganisms to under the detection limit. Inactivation of microorganisms and improving functional and powder flow characteristics by OT may have applications in dairy powder processing and food safety.