High-pressure pulses for Aspergillus niger spore inactivation in a model pharmaceutical lipid emulsion

High hydrostatic pressure (HHP) is a non-thermal process widely used in the food industry to reduce microbial populations. However, rarely its effect has been assessed in products with high oil content. This study evaluated the efficacy of HHP (200, 250, and 300 MPa) at different temperatures (25, 35, and 45 °C) by cycles (1, 2, or 3) of 10 min in the inactivation of Aspergillus niger spores in a lipid emulsion. After treatments at 300 MPa for 1 cycle at 35 or 45 °C, no surviving spores were recovered. All treatments were modeled by the linear and Weibull models. The presence of shoulders and tails in the treatments at 300 MPa at 35 or 45 °C resulted in sigmoidal curves which cannot be described by the linear model, hence the Weibull + Tail, Shoulder + Log-lin + Tail, and double Weibull models were evaluated to elucidate the inactivation kinetics. The tailing formation could be related to the presence of resistance subpopulations. The double Weibull model showed better goodness of fit (RMSE <0.2) to describe the inactivation kinetics of the treatments with the higher spore reductions. HHP at 200-300 MPa and 25 °C did not reduce the Aspergillus niger spores. The combined HHP and mild temperatures (35-45 °C) favored fungal spore inactivation. Spore inactivation in lipid emulsions by HHP did not follow a linear inactivation. HHP at mild temperatures is an alternative to the thermal process in lipid emulsions.

Lipid emulsions in clinical nutrition: Enteral and parenteral nutrition

Clinical nutrition emulsions are important products that can be life-saving for many patients suffering from gastrointestinal tract disorders, swallowing impairment, cancer, liver diseases, and many other clinical conditions. The transfer of lipids to the human body can be either intravenously (Parenteral Nutrition, PN) or through the gastrointestinal tract (Enteral Nutrition, EN). PN emulsions are considered pharmaceuticals and thus regulated accordingly. On the other hand, EN emulsions are classified as Food for Specific Medical Purposes (FSMP) and do not follow pharmaceutical regulations. Regarding product design, PN emulsions must follow theoretical emulsion formulation and production aspects, but special requirements regarding droplet size distribution must be followed to comply with national pharmacopeia monographs. Furthermore, a full clinical program on clinical evidence to prove safety and efficacy must be provided for marketing approval. On the contrary, EN emulsions require limited clinical evidence to substantiate health or clinical benefits. A short introduction to clinical nutrition with a focus on lipid emulsions is presented in this chapter. Furthermore, a general overview of the composition and main ingredients of clinical nutrition lipid emulsions is reviewed. Main clinical aspects are also mentioned here, highlighting the difficulties of clinically proving the efficacy of these products. The manufacturing and control of clinical nutrition emulsions are also reviewed, focusing on PN products and the main regulatory requirements related to the safety of these intravenous emulsions. Finally, stability and physicochemical properties are reviewed, and examples of commercially available products are used to illustrate these properties linked to the stability of these products. Lipids in clinical nutrition is a moving field and we do hope this chapter may remain a valuable source to understand newly emerging research on this topic.

Rheological Issues on Oropharyngeal Dysphagia

There is an increasing proof of the relevance of rheology on the design of fluids for the diagnosis and management of dysphagia. In this sense, different authors have reported clinical evidence that support the conclusion that an increase in bolus viscosity reduces the risks of airway penetration during swallowing. However, this clinical evidence has not been associated yet to the definition of objective viscosity levels that may help to predict a safe swallowing process. In addition, more recent reports highlight the potential contribution of bolus extensional viscosity, as elongational flows also develops during the swallowing process. Based on this background, the aim of this review paper is to introduce the lecturer (experts in Dysphagia) into the relevance of Rheology for the diagnosis and management of oropharyngeal dysphagia (OD). In this sense, this paper starts with the definition of some basic concepts on Rheology, complemented by a more extended vision on the concepts of shear viscosity and elongational viscosity. This is followed by a short overview of shear and elongational rheometrical techniques relevant for the characterization of dysphagia-oriented fluids, and, finally, an in-depth analysis of the current knowledge concerning the role of shear and elongational viscosities in the diagnosis and management of OD (shear and elongational behaviors of different categories of dysphagia-oriented products and contrast fluids for dysphagia assessment, as well as the relevance of saliva influence on bolus rheological behavior during the swallowing process).

Effect of operating parameters on the physical and chemical stability of an oil gelled-in-water emulsified curcumin delivery system

BACKGROUND

Curcumin is a natural antioxidant with important beneficial properties for health, although its low bioavailability and sensitivity to many environmental agents limits its use in the food industry. Furthermore, some studies mention a potential synergistic effect with omega-3 polyunsaturated fatty acids, comprising other bioactive compounds extremely unstable and susceptible to oxidation. A relatively novel strategy to avoid oxidation processes is to transform liquid oils into three-dimensional structures by adding a gelling agent and forming a self-assembled network that can later be vectorized by incorporating it into other systems. The present study aimed to design and optimize an oil gelled-in-water curcumin-loaded emulsion to maximize curcumin stability and minimize lipid oxidation in terms of some critical operating parameters, such as dispersed phase, emulsifier and stabilizer concentrations, and homogenization rate.

RESULTS

The operating conditions that had a significant effect on the formulation were the dispersed phase weight fraction affecting droplet size and total lipid oxidation, homogenization conditions affecting droplet size and primary lipid oxidation, and emulsifier concentration affecting droplet size (significance level = 95%). The optimal formulation for maximizing curcumin load and minimizing lipid oxidation in the oleogelified matrix was 140.4 g kg^-1 dispersed phase, 50.0 g kg^-1 emulsifier, 4.9 g kg^-1 stabilizer and homogenization speed 1016 × g.

CONCLUSION

The results obtained in the present study provide a valuable tool for the rational design and development of oil gelled-in-water emulsions that stabilize and transport bioactive compounds such as curcumin. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Combination of supercritical CO2 and high-power ultrasound for the inactivation of fungal and bacterial spores in lipid emulsions

For the first time, this study addresses the intensification of supercritical carbon dioxide (SC-CO2) treatments using high-power ultrasound (HPU) for the inactivation of fungal (Aspergillus niger) and bacterial (Clostridium butyricum) spores in oil-in-water emulsions. The inactivation kinetics were analyzed at different pressures (100, 350 and 550 bar) and temperatures (50, 60, 70, 80, 85 °C), depending on the microorganism, and compared to the conventional thermal treatment. The inactivation kinetics were satisfactorily described using the Weibull model. Experimental results showed that SC-CO2 enhanced the inactivation level of both spores when compared to thermal treatments. Bacterial spores (C.butyricum) were found to be more resistant to SC-CO2 + HPU, than fungal (A.niger) ones, as also observed in the thermal and SC-CO2 treatments. The application of HPU intensified the SC-CO2 inactivation of C.butyricum spores, e.g. shortening the total inactivation time from 10 to 3 min at 85 °C. However, HPU did not affect the SC-CO2 inactivation of A.niger spores. The study into the effect of a combined SC-CO2 + HPU treatment has to be necessarily extended to other fungal and bacterial spores, and future studies should elucidate the impact of HPU application on the emulsion's stability.

Non-thermal pasteurization of lipid emulsions by combined supercritical carbon dioxide and high-power ultrasound treatment

Supercritical carbon dioxide (SC-CO₂) is a novel method for food pasteurization, but there is still room for improvement in terms of the process shortening and its use in products with high oil content. This study addressed the effect of high power ultrasound (HPU) on the intensification of the SC-CO₂ inactivation of E. coli and B. diminuta in soybean oil-in-water emulsions. Inactivation kinetics were obtained at different pressures (100 and 350 bar), temperatures (35 and 50 °C) and oil contents (0, 10, 20 and 30%) and were satisfactorily described using the Weibull model. The experimental results showed that for SC-CO₂ treatments, the higher the pressure or the temperature, the higher the level of inactivation. Ultrasound greatly intensified the inactivation capacity of SC-CO₂, shortening the process time by approximately 1 order of magnitude (from 50 to 90 min to 5-10 min depending on the microorganism and process conditions). Pressure and temperature also had a significant (p < 0.05) effect on SC-CO₂ + HPU inactivation for both bacteria, although the effect was less intense than in the SC-CO₂ treatments. E. coli was found to be more resistant than B. diminuta in SC-CO₂ treatments, while no differences were found when HPU was applied. HPU decreased the protective effect of oil in the inactivation and similar microbial reductions were obtained regardless of the oil content in the emulsion. Therefore, HPU intensification of SC-CO₂ treatments is a promising alternative to the thermal pasteurization of lipid emulsions with heat sensitive compounds.

Freeze-drying: A relevant unit operation in the manufacture of foods, nutritional products, and pharmaceuticals

Freeze-drying, a drying unit operation frequently used in food, pharmaceutical, and biopharmaceutical industries to prolong the shelf life of labile products, is an energy-intensive, time-consuming, and expensive process. Although all three steps (freezing, primary drying, and secondary drying) of freeze-drying are important, primary drying is the longest and most critical one. As sublimation during primary drying is mainly described in terms of heat and mass transfer, the present work provides extensive theoretical and experimental analyses of these processes. First, a detailed review of the current state-of-the art of freeze-drying, focusing on the drying stage, is given, which contributes to a fundamental understanding of the drying process. Second, a detailed experimental study of the drying section of the freeze-drying process is discussed, furnishing information on the relationship between input and output process parameters during the primary drying stage and thus aiding freeze-drying process design and optimization. In this regard, the influence of primary drying input parameters (i.e., shelf temperature and chamber pressure) and vial position on output parameters such as product temperature, sublimation rate, overall vial heat transfer coefficient, and resistance to mass transfer of the dried product are extensively discussed. For all combinations of shelf temperature and chamber pressure studied herein, the highest product temperature, sublimation rate, and overall vial heat transfer coefficient are observed in front edge vials, whereas the lowest values are observed in center vials. In general, the highest sublimation rate, at a given product temperature, is observed for low chamber pressure-high shelf temperature combinations.

Use of a temperature ramp approach (TRA) to design an optimum and robust freeze-drying process for pharmaceutical formulations

Freeze-drying, until now, has been a process that was designed using a trial and error experimental approach. This approach is often material and time consuming, and the resulting freeze-drying processes are neither optimum nor robust. Accordingly, the objective of this study was to develop a simple-to-use and experimental-based approach to design an optimum and robust freeze-drying process for any given formulation. The temperature ramp approach (TRA) detailed in this study involves the implementation of a customized design of experiments (DoE) to perform few (three or four) experiments using a given drug formulation. The DoE results are analyzed to define optimum processing conditions (i.e., shelf temperature and chamber pressure) based on a predefined range of target product temperature for primary drying, which could be defined from formulation characterization at its frozen state. In this study, a successful freeze-drying process of two model formulations using the TRA was designed. Verification experiments at the optimum processing conditions showed excellent agreement in both product temperature and sublimation rate with the values obtained using the TRA. Thus, the TRA detailed in this study offers a significant advantage to reduce development time and material, and enhance the efficiency and robustness of the resulting freeze-drying process.

An Experimental-Based Approach to Construct the Process Design Space of a Freeze-Drying Process: An Effective Tool to Design an Optimum and Robust Freeze-Drying Process for Pharmaceuticals

The application of quality by design (QbD) is becoming an integral part of the formulation and process development for pharmaceutical products. An essential feature of the QbD philosophy is the design space. In this sense, a new approach to construct a process design space (PDS) for the primary drying section of a freeze-drying process is addressed in this paper. An effective customized design of experiments (DoE) is developed for freeze-drying experiments. The results obtained from the DoE are then used to construct the product-based PDS. The proposed product-based PDS construction approach has several advantages, including (1) eliminating assumptions on the heat transfer coefficient and dried product resistance, as it is constructed from experimental results specifically obtained from a given formulation, yielding more realistic and reliable results and (2) PDS construction based on a narrow range of product temperatures and considering the variations in product temperature and sublimation rate of vials across a shelf. This guarantees the effectiveness and robustness of the process and facilitates the process scale-up and transfer. The PDS developed herein was experimentally verified. The PDS predicted parameters were in excellent agreement with the experimentally obtained parameters.

Droplet-size distribution and stability of commercial injectable lipid emulsions containing fish oil

PURPOSE

The droplet size of commercial fish oil-containing injectable lipid emulsions, including conformance to United States Pharmacopeia (USP) standards on fat-globule size, was investigated.

METHODS

A total of 18 batches of three multichamber parenteral products containing the emulsion SMOFlipid as a component were analyzed. Samples from multiple lots of the products were evaluated to determine compliance with standards on the volume-weighted percentage of fat exceeding 0.05% (PFAT(5)) specified in USP chapter 729 to ensure the physical stability of i.v. lipid emulsions. The products were also analyzed to determine the effects of various storage times (3, 6, 9, and 12 months) and storage temperatures (25, 30, and 40 °C) on product stability. Larger-size lipid particles were quantified via single-particle optical sensing (SPOS). The emulsion's droplet-size distribution was determined via laser light scattering.

RESULTS

SPOS and light-scattering analysis demonstrated mean PFAT(5) values well below USP-specified globule-size limits for all the tested products under all study conditions. In addition, emulsion aging at any storage temperature in the range studied did not result in a significant increase of PFAT(5) values, and mean droplet-size values did not change significantly during storage of up to 12 months at temperatures of 25-40 °C.

CONCLUSION

PFAT(5) values were below the USP upper limits in SMOFlipid samples from multiple lots of three multichamber products after up to 12 months of storage at 25 or 30 °C or 6 months of storage at 40 °C.