Liliana Alamilla-Beltrán

Morphological and physicochemical characterization of agglomerates of titanium dioxide nanoparticles in cell culture media

Titanium dioxide nanoparticles (TiO2 NP) are possible carcinogenic materials (2B-IARC) and their toxicity depends on shape, size, and electrical charge of primary NP and on the system formed by NP media. The aim of this work was to characterize agglomerates of three TiO2 NP by evaluating their morphometry, stability, and zeta potential (ζ) in liquid media and their changes with time. Sizes of agglomerates by dynamic light scattering (DLS) resulted to be 10-50 times larger than those obtained by digital image analysis (DIA) given the charged zone around particles. Fractal dimension (FD) was highest for agglomerates of spheres and belts in F12K, and in E171 in FBS media. E171 and belts increased FD with time. At time zero, using water as dispersant FD was larger for agglomerates of spheres than for of E171. Belts suspended in water had the smallest values of circularity (Ci) which was approximately unchanged with time. All dispersions had ζ values around -30 mV at physiological pH (7.4) and dispersions of NP in water and FBS showed maximum stability (Turbiscan Lab analysis). Results help in understanding the complex NP geometry-size-stability relationships when performing in vivo and in vitro environmental-toxicity works and help in supporting decisions on the usage of TiO2 NP.

Water droplet spreading and recoiling upon contact with thick-compact maltodextrin agglomerates.

BACKGROUND The food and pharmaceutical industries handle a number of compounds in the form of agglomerates which must be put into contact with water for rehydration purposes. In this work, liquid-solid interaction between water and maltodextrin thick-compact agglomerates was studied at different constituent particle sizes for two compression forces (75 and 225 MPa). RESULTS Rapid droplet spreading was observed which was similar in radius to the expected one for ideal, flat surfaces. Contact angle determinations reported oscillations of this parameter throughout the experiments, being indicative of droplet recoiling on top of the agglomerate. Recoiling was more frequent in samples obtained at 225 MPa for agglomerate formation. Agglomerates obtained at 75 MPa exhibited more penetration of the water. Competition between dissolution of maltodextrin and penetration of the water was, probably, the main mechanism involved in droplet recoiling. Micrographs of the wetting marks were characterized by means of image analysis and the measurements suggested more symmetry of the wetting mark at higher compression force. CONCLUSION Differences found in the evaluated parameters for agglomerates were mainly due to compaction force used. No significant effect of particle size in recoiling, penetration of water into the agglomerate, surface texture and symmetry was observed.

Effects of Storage Temperature and Water Activity on the Degradation of Carotenoids Contained in Microencapsulated Chili Extract

The aim of this work was to evaluate the effects of storage temperature and water activity on degradation of carotenoids contained in microencapsulates of non-aqueous extracts from chili (NAEC). Total carotenoids content and adsorption isotherms of microencapsulated NAEC in a 1:1 weight ratio with gum Arabic-maltodextrin DE 20 (GA 50%–MD50%) were determined at 25, 35, and 40°C. The isotherms were fitted using the Guggenheim-Anderson-de-Boer model and their enthalpies and entropies, both differential and integral, were estimated by the Clausius-Clapeyron method. The minimum integral entropy was considered as the point of maximum stability at which water less readily participates in degradation reactions. Zones of minimum integral entropy were found between 7.56–8.30, 6.10–6.95, and 5.15–6.04 kg H2O/100 kg dried solids, corresponding to water activity (aw) of 0.210–0.239, 0.238–0.277, and 0.262–0.313 at 25, 35, and 40°C, respectively. Total carotenoids content (CT) degraded over time, but degradation of carotenoids was lower in microcapsules stored at 25°C than those stored at 35 or 40°C. The morphology of microcapsules was altered at aw > 0.6, including swelling of the polysaccharide matrix was presented, and possible subsequent dissolution of the wall material, which indicates a high rate of carotenoid degradation. When microencapsulated NAEC were storage between 0.2–0.6 of water activity, the highest glass transition temperatures were achieved. In this range, the wall materials of the microcapsules suffer less microstructural modifications, associated with the minimum level of degradation of carotenoids. Sometimes, in this water activity range, the zones of minimal entropy were observed.

Morphometric Analysis of Transverse Surface of Fractured Maltodextrin Agglomerates

Fracture creates complex surfaces. The aim of this work was to characterize the irregular surface generated in the fracture of maltodextrin thick-agglomerates using gray level intensities and texture features extracted by digital image analysis. Results showed that particle size had no significant effect on texture features and had a significant interaction with load. A 50 N load caused rougher surfaces, while a 500 N load produced smooth surfaces. Obtained values of texture fractal dimension were not higher than 2.23 and were related to image entropy.

Zeta Potential of Food Matrices

Food matrices contain electrically charged particles, which interact with each other and with the media and are produced via several interface processes and mechanisms. The understanding of electric charge interactions is complex and essential towards the development of food systems since they can determine the type of particle-particle and particle-media interactions. They strongly affect stability, rheological behavior, sedimentation, re-dispersion, filtration, shelf life, texture, flavor, and color; thus, importantly influencing food structure and stability. One of the most useful parameters that allow the study of electric interactions in food systems is the zeta potential (ZP). It is possible to find a variety of laboratory instruments designed for its evaluation. ZP is an important property for the characterization of dispersed systems in which sample preparation and measuring methods play a key role to obtain reliable and reproducible results. The use of this parameter has increased in a number of fluid food systems such as alcoholic beverages, juices, extracts, coffee, milk, yoghurt, and edible films, most of which are described in this review. There is a wide amplitude in the number of relevant publications in the literature involving ZP for different products and this is reflected in the length of the different sections of this document. This work depicts a thorough review of the main theoretical principles, applications, and relevance of this parameter in food science and technology.

Effect of traditional dehydration processing of pepper jalapeno rayado (Capsicum annuum) on secondary metabolites with antioxidant activity

ABSTRACT Jalapeno rayado peppers (Capsicum annuum) are usually subjected to a traditional smoke-dehydration process using Quercus sp. This treatment provides peppers with their characteristic functional attributes. To differentiate the production of antioxidant metabolites during the dehydration-smoking process, this process was compared with convective dehydration, both at 60°C. A higher antioxidant activity in smoke-dried pepper was observed due to the increase in concentration of phenolic compounds, flavonoids and Maillard products in the last hours of the process and was related to the presence of radicals with m/z (-) values: 585.32, 292.2, 326.18, 653.28, 240.11 and 210.14, generated during both dehydration processes. The change in colour was mainly due to the increase of Maillard compounds. Convective dehydration favoured the extraction of capsaicinoids, whereas no significant change was observed in smoke-dehydration, and carotenoid degradation was 40% with either process. A similar final moisture content was achieved in both processes.

Food Preservation by Nanostructures-Water Interactions Control

Understanding structure–function properties in food systems has led to possibilities of food preservation by managing product structural features so that water and nutriments are subjected to various levels of physical immobilization, thus reducing reactivity and allowing a better control of product stability. In this chapter it is noted that to achieve this, it is necessary to induce in the solid matrix of the product the formation of micro–nano cavities, fissures, and pores into which water and other substances will strongly (and tightly) bound. Important thermodynamic characteristics of the system control this reduction in mobility and entropy control of food matrix-liquid is aimed to achieve the task. Also, principles and practical applications of such processes are discussed as well as structural features-appraisal methodologies.

Antioxidant Activity of Microencapsulated Capsicum annuum Oily Extract Obtained by Spray Drying

There is great interest today in development of food additives obtained from vegetables and fruits, due to the presence of phytochemicals and the potential use of these substances as functional ingredients. Chiles are used in the manufacture of condiments and food formulations because of their pigmentation and flavor. In addition to its provitamin and antimicrobial properties (Acero-Ortega et al. 2005), Capsicum has shown antioxidant activity because of its content of polyphenolic compounds and carotenoids. Carotenoid consumption has been associated with a lower risk of developing chronic degenerative diseases (Matsufuji et al. 1998; Dutta et al. 2005). In some studies, certain carotenoids were identified in the fruits of dry chile (Capsicum annuum L. grosum Sendt), such as β-carotene, α-carotene, β-cryptoxanthin, zeaxanthin, lutein, capsanthin, capsorubin, and criptocapsina (Collera-Zuniga et al. 2005). Carotenoids can be extracted from chile’s natural matrix in order to use their properties as phytochemicals; however, due to the unsaturated nature of chile’s molecular structure, once carotenoids are extracted, they can be modified by isomerization and subsequent oxidative degradation, resulting in the loss of antioxidant activity with formation of fractions carotenoids called apocarotenoids (Maoka et al. 2001).

Hydrodynamic Characterization of the Formation of Alpha-Tocopherol Nanoemulsions in a Microfluidizer

The use of nanoemulsions produced by microfluidization as delivery systems for nonpolar functional compounds such as bioactive lipids, drugs, flavors, and antioxidants has raised increasing interest mainly in food, pharmaceutical, and cosmetic industries. Despite the high surface-to-volume ratio handled in fluid microchannels, which is beneficial for the higher mass and heat transfer (with a shorter residence time), the small cross-section is a major disadvantage for achieving a good mixture. A commonly used technique to understand and characterize flow in micromixers is the determination of residence time distribution (RTD). This distribution allows determining the effect of mixing on the behavior of a fluid by knowing the mean residence time of molecules within the channels and thus achieving a process design leading to improved product quality. This time, must be adequate to allow the breakdown of the droplets and absorption of emulsion compounds.

Caking Process and Microstructural Changes of Wall Materials Used in Spray-Drying Process

Microencapsulation process is applied to protect the core material or active agent against environmental factors and helps resist brittle material processing conditions improving flavor, aroma, stability, nutritional value, and appearance. Microencapsulation applications are found in agricultural, pharmaceutical, food, cosmetics, and fragrance industries (Madene et al. 2006). The retention of the active agent in this process is governed, among other factors, by type of wall material, so its selection is an important step. The most commonly used materials include carbohydrates such as maltodextrin (MD) and gum arabic (GA) and proteins such as whey and soy protein isolate (SPI) (Madene et al. 2006; Matalanis et al. 2011). During microencapsulation process, the final products are in the form of powder containing individual microparticles, agglomerates, or both. The food powders containing amorphous carbohydrates could experiment physical changes as stickiness and caking when the powder is exposed to temperature above the powder’s glass transition temperature (T g ). This temperature is a function of the moisture content and water activity (a w ) of the powder (Foster et al. 2005; Schebor et al. 2010). At the T g , the viscosity of amorphous materials decreases significantly, allowing greater molecular mobility, which has effect in sticky behavior (Foster et al. 2005). The caking of food powders is an unwanted and very common problem that occurs during processing, handling, and storage. The particles of amorphous powders may progressively be deformed until they stick to each other and, eventually, form great agglomerates (Saragoni et al. 2007). This phenomenon is affected by microstructure and hygroscopicity; however, other facts are reported as decisive like stress, humidity, and temperature for caking mechanism and caking kinetics (Hartmann and Palzer 2011). The caking phenomenon reduces the product quality and functionality, rehydration, dispersibility, and the shelf life and increases deterioration of organoleptic quality and the formation of lumps and agglomerates (Lipasek et al. 2012). Microscopy techniques have been applied to analyze powder microstructure, identifying useful factors to describe changes observed during processing and storage (Guadarrama-Lezama et al. 2014).