The impacts of protein concentration, milk solids content and heat/run time "AGING" on the fouling and cleaning of a dairy heat exchange surface

The mechanisms of the fouling and cleaning processes of dairy heat exchangers are affected by various factors such as the bulk fluid protein concentration, the bulk fluid solids content and the heating/run time 'aging' during the processing of dairy fluids. Little has been published about the effect of the last two factors on the fouling and cleaning processes in dairy plants. In this study, laboratory produced heat induced whey protein gels (HIWPGs), and fouling layers from different dairy solutions (produced using a pilot-scale test rig) were used to investigate the effect of protein concentration, milk solids content and heating/run time on the fouling and cleaning of dairy heat exchange surfaces. HIWPGs were used, because they are considered to be a suitable model material for studying proteinaceous milk fouling. This is because HIWPGs have the same nature as type "A" milk fouling and they are easy to reproduce and to dissolve in the laboratory under well-controlled conditions. The results from the HIWPGs investigations provided a good foundation for the pilot-plant investigation. In the HIWPGs studies, the effect of protein concentration and the effect of the heating/run time on the formation and dissolution of HIWPGs were investigated using HIWPGs made from different protein concentrations (14, 20, and 26 wt %) and HIWPGs produced at various heating times (60, 120,240, 1440 and 2880 minutes). The HIWPGs were formed in tubular capsules and then dissolved in aqueous sodium hydroxide at an optimal condition of 0.5 wt % at 60°C. The dissolution rate calculation was based on a UV Spectrophotometer analysis. The microstructure and texture of the HIWPGs was analysed using scanning electron microscope (SEM) and texture analyser. It was found that increasing the HIWPGs protein concentration from 17 wt % to 26 wt % significantly increased the gel hardness and the penetration force from approximately 8N to 48N and decreased the dissolution rate from 0.34 g m-2 S-1 to 0.12 g m-2 S-I. It was also found that increasing the heating time from 60 min to 1440 mm significantly increased the gel hardness and penetration force from approximately 3N to 25N, and decreased the dissolution rate from 0.40 g m-2 S-1 to 0.24 g m-2 S-I. The HIWPGs contained larger aggregates and the structure became more rigid, implicating the difficulty in cleaning. In the pilot-scale plant studies, the effects of bulk protein concentration, bulk solids content and heating/run time on the fouling and cleaning of dairy heat exchange surfaces were investigated using fouling layers produced from different concentrations of whey protein fluid, different solids content of milk fluid and fouling layers produced at various heating/run times. The fouling layers were produced by re-circulating the dairy fluids in the pilot-scale test rig. The dairy fluids used include: reconstituted whey protein, fresh whole milk, fresh skim milk, reconstituted whole milk, and reconstituted skim milk. The cleaning of the fouling layers was achieved by re-circulating aqueous sodium hydroxide (0.5 wt %) at 60°C, and the cleaning efficiency was monitored in the form of the recovery of the overall heat transfer coefficient while both fluid electric conductivity and turbidity were recorded as an indication of the cleaning completion. The microstructure structure of the fouling deposits was analyzed usmg scanmng electron microscope. It was found that the pilot-scale plant study results mirror the results from the HIWPGs study, increases in the bulk protein concentration, bulk solids content and the heating/run time in the pilot plant study significantly increased both the rate of fouling and the time required to remove the fouling deposit. The slopes of the overall heat transfer coefficient versus time in the cleaning curves provide a good indication of the effect of bulk protein concentration, bulk solids content and aging, particularly for the fouling formed at the earliest stage (the inner fouling layer). The inner fouling layers were affected by the initial high bulk concentration and experienced the longest aging period during the heating time, and they were the hardest to clean. Contribution of this research This research has contributed reliable data for improving the understanding of the effect of protein concentration; solids content and dairy fluids heating/run time on the fouling and cleaning of dairy heat exchangers, and will provide a strong basis and guide the decision for further studies

The impacts of protein concentration, milk solids content and heat/run time "AGING" on the fouling and cleaning of a dairy heat exchange surface

The mechanisms of the fouling and cleaning processes of dairy heat exchangers are affected by various factors such as the bulk fluid protein concentration, the bulk fluid solids content and the heating/run time 'aging' during the processing of dairy fluids. Little has been published about the effect of the last two factors on the fouling and cleaning processes in dairy plants. In this study, laboratory produced heat induced whey protein gels (HIWPGs), and fouling layers from different dairy solutions (produced using a pilot-scale test rig) were used to investigate the effect of protein concentration, milk solids content and heating/run time on the fouling and cleaning of dairy heat exchange surfaces. HIWPGs were used, because they are considered to be a suitable model material for studying proteinaceous milk fouling. This is because HIWPGs have the same nature as type "A" milk fouling and they are easy to reproduce and to dissolve in the laboratory under well-controlled conditions. The results from the HIWPGs investigations provided a good foundation for the pilot-plant investigation. In the HIWPGs studies, the effect of protein concentration and the effect of the heating/run time on the formation and dissolution of HIWPGs were investigated using HIWPGs made from different protein concentrations (14, 20, and 26 wt %) and HIWPGs produced at various heating times (60, 120,240, 1440 and 2880 minutes). The HIWPGs were formed in tubular capsules and then dissolved in aqueous sodium hydroxide at an optimal condition of 0.5 wt % at 60°C. The dissolution rate calculation was based on a UV Spectrophotometer analysis. The microstructure and texture of the HIWPGs was analysed using scanning electron microscope (SEM) and texture analyser. It was found that increasing the HIWPGs protein concentration from 17 wt % to 26 wt % significantly increased the gel hardness and the penetration force from approximately 8N to 48N and decreased the dissolution rate from 0.34 g m-2 S-1 to 0.12 g m-2 S-I. It was also found that increasing the heating time from 60 min to 1440 mm significantly increased the gel hardness and penetration force from approximately 3N to 25N, and decreased the dissolution rate from 0.40 g m-2 S-1 to 0.24 g m-2 S-I. The HIWPGs contained larger aggregates and the structure became more rigid, implicating the difficulty in cleaning. In the pilot-scale plant studies, the effects of bulk protein concentration, bulk solids content and heating/run time on the fouling and cleaning of dairy heat exchange surfaces were investigated using fouling layers produced from different concentrations of whey protein fluid, different solids content of milk fluid and fouling layers produced at various heating/run times. The fouling layers were produced by re-circulating the dairy fluids in the pilot-scale test rig. The dairy fluids used include: reconstituted whey protein, fresh whole milk, fresh skim milk, reconstituted whole milk, and reconstituted skim milk. The cleaning of the fouling layers was achieved by re-circulating aqueous sodium hydroxide (0.5 wt %) at 60°C, and the cleaning efficiency was monitored in the form of the recovery of the overall heat transfer coefficient while both fluid electric conductivity and turbidity were recorded as an indication of the cleaning completion. The microstructure structure of the fouling deposits was analyzed usmg scanmng electron microscope. It was found that the pilot-scale plant study results mirror the results from the HIWPGs study, increases in the bulk protein concentration, bulk solids content and the heating/run time in the pilot plant study significantly increased both the rate of fouling and the time required to remove the fouling deposit. The slopes of the overall heat transfer coefficient versus time in the cleaning curves provide a good indication of the effect of bulk protein concentration, bulk solids content and aging, particularly for the fouling formed at the earliest stage (the inner fouling layer). The inner fouling layers were affected by the initial high bulk concentration and experienced the longest aging period during the heating time, and they were the hardest to clean. Contribution of this research This research has contributed reliable data for improving the understanding of the effect of protein concentration; solids content and dairy fluids heating/run time on the fouling and cleaning of dairy heat exchangers, and will provide a strong basis and guide the decision for further studies

Effects of the Sous Vide and Conventional Electric Oven Cooking Methods on the Physio-Sensory Quality Attributes of Arabian Camel (<i>Camelus dromedarius</i>) Meat

This study aimed to evaluate the effect of the sous vide and electric oven cooking methods on the physical and sensory characteristics of camel meat. A combination of 4 cooking temperatures (70, 80, 90, and 100 °C) and 6 cooking times (30, 60, 90, 120, 150, and 180 min) was applied. Both methods significantly affected the meat’s physical properties (pH, cooking loss, density, lightness, redness, and yellowness color components), except for water activity. Furthermore, the cooking temperature and time significantly affected all the sensory properties (tenderness, flavor, juiciness, and general acceptance). The cooking loss was the only parameter affected significantly by the interaction of the cooking method, cooking temperature, and cooking time. It is concluded that the sous vide method is the more suitable method for cooking camel meat compared to the electric oven method considering the cooking temperature and time. Further studies are recommended to estimate energy consumption for both cooking methods evaluated in this study aiming at reducing the overall power expenditure

Pulsed Electric Field as a Novel Technology for Fresh Barhi Date Shelf-Life Extension: Process Optimization Using Response Surface Methodology

Fresh dates of the Barhi cultivar at the Khalal maturity stage are well known for their pleasant taste, crispy texture, and bright yellow color. One of the primary technical challenges is preserving the initial high-quality fresh Khalal Barhi dates and extending their shelf life for the longest possible period after harvesting and during the marketing process. Resolving this problem would permit the export of high-quality fresh Saudi dates to international markets. Therefore, the main aim of this study is to evaluate the feasibility of utilizing a pulsed electric field as a novel non-thermal postharvest processing technology for preserving the nutritional, microbiological, and physical quality of Barhi dates during storage at different temperatures and durations. To accomplish this goal, a five-factor mixed-level central composite rotating design (CCRD) with a response surface methodology (RSM) model was used to define the best PEF processing conditions and subsequent storage environments. The influence of independent factors, PEF intensity (10, 20, 30, and 40 kV/cm), PEF exposure time (40, 80, 120, and 160 ms), PEF numbers (50, 100, 150, and 200 pulses), storage temperature (1 &deg;C, 5 &deg;C, 15 &deg;C, and 25 &deg;C), and storage time (1 day, 6 days, 11 days, 16 days, and 21 days), on the total soluble solids, firmness, total color changes, total viable count, total phenolic content, DPPH antiradical activity, fructose, and glucose were assessed. The results indicated the optimal conditions of PEF treatment and subsequently storage conditions for conserving the quality and elongating the storability of fresh Barhi dates were: 10.3 kV/cm PEF intensity; 46.73 ms PEF duration; number of PEF, is 169.9 pulses; 18.7 &deg;C storage temperature; and 21 days&rsquo; storage time. At the aforementioned optimal conditions, the values of total soluble solids (TSS), firmness, &Delta;E, total viable count (TVC), total phenolic content (TPC), DPPH antiradical activity, glucose, and fructose were 41.44%, 62.47 newton, 0.1, 0.098 log CFU/g, 1.29 mg GAE/g, 65.95%, 3.45, and 3.44, respectively. These values were comparable to the predicted values (Desirability value = 1), indicating that the applied RSM models were ideal for optimizing the PEF and storage conditions for preserving the quality and prolonging the fresh Barhi dates&rsquo; shelf life. Overall, the ideal PEF treatment and storage conditions for sustaining the quality characteristics of Barhi dates during an extended storage time were identified in this study

Pulsed Electric Field as a Novel Technology for Fresh Barhi Date Shelf-Life Extension: Process Optimization Using Response Surface Methodology

Fresh dates of the Barhi cultivar at the Khalal maturity stage are well known for their pleasant taste, crispy texture, and bright yellow color. One of the primary technical challenges is preserving the initial high-quality fresh Khalal Barhi dates and extending their shelf life for the longest possible period after harvesting and during the marketing process. Resolving this problem would permit the export of high-quality fresh Saudi dates to international markets. Therefore, the main aim of this study is to evaluate the feasibility of utilizing a pulsed electric field as a novel non-thermal postharvest processing technology for preserving the nutritional, microbiological, and physical quality of Barhi dates during storage at different temperatures and durations. To accomplish this goal, a five-factor mixed-level central composite rotating design (CCRD) with a response surface methodology (RSM) model was used to define the best PEF processing conditions and subsequent storage environments. The influence of independent factors, PEF intensity (10, 20, 30, and 40 kV/cm), PEF exposure time (40, 80, 120, and 160 ms), PEF numbers (50, 100, 150, and 200 pulses), storage temperature (1 °C, 5 °C, 15 °C, and 25 °C), and storage time (1 day, 6 days, 11 days, 16 days, and 21 days), on the total soluble solids, firmness, total color changes, total viable count, total phenolic content, DPPH antiradical activity, fructose, and glucose were assessed. The results indicated the optimal conditions of PEF treatment and subsequently storage conditions for conserving the quality and elongating the storability of fresh Barhi dates were: 10.3 kV/cm PEF intensity; 46.73 ms PEF duration; number of PEF, is 169.9 pulses; 18.7 °C storage temperature; and 21 days’ storage time. At the aforementioned optimal conditions, the values of total soluble solids (TSS), firmness, ΔE, total viable count (TVC), total phenolic content (TPC), DPPH antiradical activity, glucose, and fructose were 41.44%, 62.47 newton, 0.1, 0.098 log CFU/g, 1.29 mg GAE/g, 65.95%, 3.45, and 3.44, respectively. These values were comparable to the predicted values (Desirability value = 1), indicating that the applied RSM models were ideal for optimizing the PEF and storage conditions for preserving the quality and prolonging the fresh Barhi dates’ shelf life. Overall, the ideal PEF treatment and storage conditions for sustaining the quality characteristics of Barhi dates during an extended storage time were identified in this study