Microwave Processing: Current Background and Effects on the Physicochemical and Microbiological Aspects of Dairy Products.

Overheating is still a major problem in the use of conventional heating for milk and various dairy products, because it leads to the lowering of quality and sensory and nutritional values. Microwave (MW) heating has been credited with providing superior-quality dairy-based products with extended shelf-life, representing a good alternative to conventional heat treatment. The main drawback of MW heating refers to nonuniform temperature distribution, resulting in hot and cold spots mainly in solid and semisolid products; however, MW heating has been shown to be suitable for liquid foods, especially in a continuous fluid system. This review aims to describe the main factors and parameters necessary for the application of MW heating technology for dairy processing, considering the theoretical fundamentals and its effects on quality and safety aspects of milk and dairy products. MW heating has demonstrated great ability for the destruction of pathogenic/spoilage microorganisms and their spores, and also inactivation of enzymes, thereby preserving fresh characteristics of dairy products.

Ultrasound pre-treatment prior to unripe banana air-drying: effect of the ultrasonic volumetric power on the kinetic parameters.

Aiming to decrease the water content during the air-drying process of unripe banana slices, ultrasound (US) pre-treatments (25 °C) for 20 and 25 min at 9.38 and 25.63 W/L ultrasonic volumetric power were evaluated. Air-drying was performed at 50 and 60 °C for 360 min. Unripe banana slices pretreated at 25.63 W/L did not improve water migration, under either air-drying temperature, while slices pretreated at 9.38 W/L resulted in an increase in water effective diffusivity of 4.8 and 13.7% at 20 min US + air-drying at 50 °C and 25 min US + air-drying at 60 °C, respectively. The drying time saving of 7% and 9%, respectively, was achieved, showing that these treatments were alternative for processing unripe banana slices. Thus, ultrasound and air-drying operational parameters required accurately defined to achieve desirable results. Experimental data were adjusted to four models and the Midilli model resulted in the best experimental data fit, with r 2 > 0.9988, RMSE < 0.0873 and χ2 < 0.00996.

Use of alpha-amylase and amyloglucosidase combinations to minimize the bread quality problems caused by high levels of damaged starch.

The objective of this work was to investigate the contribution of α-amylase and amyloglucosidase to dough fermentation process and bread quality, as an alternative to reduce the negative effects caused by high damaged starch in flour. The dough properties during the proofing process were modified by higher damaged starch content. Higher damaged starch in flour resulted into breads with darker crusts and firmer crumbs. The enzymes reduced the negative influence of damaged starch, producing a positive effect on the maximum carbon dioxide pressure reached during fermentation and the carbon dioxide volume retained by dough. Incorporation of alpha-amylase reduced dimension ratio and crumb firmness attributes; however, progressive additions of this additive produced lower bread volume and red intensity, and higher crumb firmness. The amyloglucosidase additions produced higher bread volume and red intensity of the crust, and lower brightness crust and gas cell diameter. Incorporation of amyloglucosidase was beneficial in the presence of a suitable quantity of damaged starch. The results confirmed that the α-amylase and amyloglucosidase additions significantly improved bread quality. Incorporation of α-amylase and amyloglucosidase led to higher bread loaves and lower crumb firmness throughout the storage period, promoting a longer life of the finished product.

The Importance of Heating Unit Operations in the Food Industry to Obtain Safe and High-Quality Products.

Civilization has begun around 3,500 BCE in Mesopotamia and the realization by people that they could manipulate food to preserve it, through sun drying, fermentation, freezing in the snow, or cooking by fire, was an important factor for the nomadic humans to start settling. Food by nature is subject to spoilage and the application of any kind of preservation method enables storage and weighted consumption. Throughout human history, many techniques have been developed and improved such as heat treatment, drying, freezing, extraction, mixing and the use of preservatives, among others. In the food industry of the modern world, each technique is implemented through sequential steps, known as unit operations. This opinion paper presents an overview of the main heating unit operations used in the food industry, highlighting their benefits to converting raw materials into palatable products with high quality and safe for consumption. Examples are presented to illustrate how several food products available in the market were submitted only to physical transformations based on scientific knowledge. However, there is a range of intensity in physical processing and the applied energy level depends on the nature of the food, target microorganism, storage conditions, type of packaging, and desired shelf-life. The importance of food safety is stressed since processed foods have been criticized for confusion between nutritious values and processing steps. There are still many challenges to the food industry to design the process in optimal conditions for food quality and with less environmental impacts and novel thermal and non-thermal technologies have been studied and implemented.

Applying the concept of state diagram on the stability analysis of an NSP-rich ingredient extracted from overripe bananas (Musa cavendishii var. Nanicão).

In this work, an ingredient containing non-starch polysaccharides (NSP), obtained from overripe bananas, was characterized using differential scanning calorimetry (DSC) and vapor sorption isotherms. Soluble sugars from overripe bananas were extracted using ethanol, resulting in a solid NSP-rich fraction. The physical properties of this new ingredient and its response to temperature and water interactions are needed for its application as a fiber flour aggregate in food preparations. Results from thermal analyses, including gelatinization, glass transition and fusion, allowed building state diagrams, then compared to vapor sorption isotherms which resulted similar to a Brunauer-Emmet-Teller (BET) type III isotherm at 25 °C, for NSP and standards samples as arabinoxylan and polygalacturonic acid. A good fit was obtained for the glass transition curves using the Kwei model. This approach enabled us to explore the stability of the material, regarding safety limits for microbial deterioration and structural changes due to glass transition.

Ozonation of cassava starch to produce biodegradable films.

In this study, biodegradable films were produced from cassava starch modified by ozone at different levels. The films were produced by casting technique using native and ozonated cassava starch, glycerol as the plasticizer, and water as the solvent. Films were characterized in term of their mechanical, barrier and functional properties, morphology, crystallinity, colour, and opacity. The morphology of the ozonated films was more homogeneous in comparison to the films produced with the non-modified starch and enhanced properties were achieved. Films produced with ozonated cassava starch presented higher tensile strength, Young's modulus and lower elongation. The water vapour permeation and the oxygen permeation were increased by increasing the ozonation time. Moreover, ozone processing resulted in films with a more hydrophilic surface and lower solubility after 24 h. Possible explanations and applications were discussed. In conclusion, the ozone processing showed to be a good alternative for starch based packaging production.

Preparation and characterization of bio-nanocomposite films based on cassava starch or chitosan, reinforced with montmorillonite or bamboo nanofibers.

In this study, films based on two different polysaccharides (chitosan and cassava starch) were produced by casting technique and nanostructured by montmorillonite (MMTNPs) or bamboo nanofibers (BNFs) at two different concentrations: 0.5g/100g and 1.0g/100g of polymer, using glycerol as plasticizer at concentration of 30g/100g of polymer. The particle size and surface charge of the MMTNPs and BNFs nanoparticles were 315±14nm and 60±3nm and -31.78mV and -20.77mV, respectively. In relation to the mechanical properties, the nanofibers increased the tensile strength in 50% of starch films, while the elongation at break shows a similar increase (66%) for both types of nanoparticles at concentration of 1.0g/100g. Cassava starch films showed a better response to nanostructure process, noticed through by the mechanical properties. XRD analyses showed good interaction between the polymer matrix and bamboo nanofibers.

Impregnation of cinnamaldehyde into cassava starch biocomposite films using supercritical fluid technology for the development of food active packaging.

In this work, supercritical solvent impregnation (SSI) has been tested for the incorporation of natural compounds into biocomposite materials for food packaging. Cinnamaldehyde, with proved antimicrobial activity against fungi commonly found in bread products, was successfully impregnated on biocomposite cassava starch based materials using supercritical carbon dioxide as solvent. Different process experimental conditions were tested (pressure, impregnation time and depressurization rate) at a fixed temperature (35 °C) in order to study their influence on the amount of impregnated cinnamaldehyde as well as on the morphology of the films. Results showed that all conditions permitted to impregnate antimicrobial active amounts superior to those previously obtained using conventional incorporation methods. Moreover, a significant decrease of the equilibrium water vapor sorption capacity and water vapor permeability of the films was observed after SSI processing which is a clear advantage of the process, considering the envisaged applications.