Relationships between morphometrical properties and the texture of an extrusion-expanded snack made from squid mantle (Dosidicus gigas)

Quality of Refrigerated Squid Mantle Cut Treated with Mint Extract Subjected to High-Pressure Processing

Squid (Loligo vulgaris) is commonly prone to spoilage, leading to a short shelf-life. High-pressure processing (HPP) can play a role in maintaining the quality and freshness of squid. Along with HPP, food preservatives from natural sources such as mint extract (ME), which are effective, safe, available, and cost-effective, are required. The present study aimed to investigate the combined effect of ME and HPP on the quality of refrigerated squid mantle cuts (SMC) over a period of 15 days. The time-kill profiles of ME and planktonic cell inactivation by HPP were assessed. ME (400 mg/L) inhibited bacterial growth, while planktonic cells treated with HPP (400 MPa) exhibited a reduction at 5 min. Physicochemical and microbial qualities of SMC treated with ME (0, 200, 400 mg/L) followed by HPP (0.1, 200, 400 MPa) for 5 min were monitored during refrigerated storage. Samples treated with ME (400 mg/L) and HPP (400 MPa) exhibited lower weight loss, cooking loss, pH changes, volatile base content, microbial counts, and higher textural properties than other samples. Based on next-generation sequencing results, Brochothrix campestris from family Listeriaceae was the predominant spoilage bacteria in treated sample after 12 days of storage. Therefore, ME and HPP combined treatments exhibited effectiveness in extending the shelf-life of refrigerated SMC.

A comprehensive study from the micro- to the nanometric scale: Evaluation of chilling injury in tomato fruit (Solanum lycopersicum)

Tomato fruit is susceptible to chilling injury (CI) during its postharvest handling at low temperature. The symptoms caused by this physiological disorder have been commonly evaluated by visual inspection at a macro-observation scale on fruit surface; however, the structure at deeper scales is also affected by CI. This work aimed to propose a descriptive model of the CI development in tomato tissue under the micro-scale, micro-nano-scale and nano-scale approaches using fractal analysis. For that, quality and fractal parameters were determined. In this sense, light microscopy, Environmental Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM) were applied to analyse micro-, micro-nano- and nano-scales, respectively. Results showed that the morphology of tomato tissue at the micro-scale level was properly described by the multifractal behaviour. Also, generalised fractal dimension (Dq=0) and texture fractal dimension (FD) of CI-damaged pericarp and cuticle were higher (1.659, 1.601 and 1.746, respectively) in comparison to non-chilled samples (1.606, 1.578 and 1.644, respectively); however, FD was unsuitable to detect morphological changes at the nano-scale. On the other hand, lacunarity represented an appropriate fractal parameter to detect CI symptoms at the nano-scale due to differences observed between damaged and regular ripe tissue (0.044 and 0.025, respectively). The proposed multi-scale approach could improve the understanding of CI as a complex disorder to the development of novel techniques to avoid this postharvest issue at different observation scales.

Comparative Evaluation of the Thermal, Structural, Chemical and Morphological Properties of Bagasse from the Leaf and Fruit of Bromelia hemisphaerica Lam. Delignified by Organosolv

Bromelia hemisphaerica Lam., a wild plant native to Mexico, has medicinal attributes and is mainly used for its hemisphericin content in foods. However, the residues of its leaves and fruits are underutilized, representing an area of opportunity for foods or materials. Lignocellulosic material from leaves and fruit bagasse was isolated using an organosolv treatment to separate their components (cellulose, hemicellulose and lignin) and to determine the influence after processing on the physicochemical, thermal and microstructural characteristics. The extracted fiber presented a cellulose content of 44% in the leaf and 33.5% in the fruit. The release of lignin after the organosolv process represented a greater amount of amorphous material in the leaf than in the fruit. By FTIR and X-ray diffraction (DRx), the change in the crystallinity of the cellulose was determined (from 18% higher in the leaf than the fruit before to 14% higher in the fruit after the organosolv process), with values similar to type I cellulose. The thermal properties showed a high order in the structure of the cellulose. Microscopy and digital analysis techniques showed the microstructural changes and the effectiveness of delignification during the process. It is concluded that the leaf fiber of B. hemisphaerica presents characteristics that make it useful as a potential ingredient for food product development and other uses.

Comparative Analysis of Fermentation Conditions on the Increase of Biomass and Morphology of Milk Kefir Grains

Kefir grains represent a symbiotic association group of yeasts, lactic acid bacteria and acetic acid bacteria within an exopolysaccharide and protein matrix known as kefiran. The mechanism of growth of a biomass of kefir after successive fermentations and optimal conditions is not well understood yet. Biomass growth kinetics were determined to evaluate the effects of temperatures (10 °C to 40 °C) and different substrates, such as monosaccharides (fructose, galactose, glucose), disaccharides (lactose, saccharose) and polysaccharides (Agave angustifolia fructans) at 2%, in reconstituted nonfat milk powder at 10% (w/v) and inoculated with 2% of milk kefir grain (105 CFU/g), after determining the pH kinetics. The best conditions of temperature and substrates were 20 °C and fructans and galactose. An increase in cells, grain sizes and a change in the morphology of the granules with the best substrates were observed using environmental scanning electron microscopy, confocal laser scanning microscopy and Image Digital Analysis (IDA). Kefir grains with agave fructans as their carbon source showed the higher fractal dimension (2.380), related to a greater co-aggregation ability of LAB and yeasts, and increase the formation of exopolysaccharides and the size of the kefir grains, which opens new application possibilities for the use of branched fructans as a substrate for the fermentation of milk kefir grains for the enhancement of cellular biomasses and exopolysaccharide production, as well as IDA as a characterization tool.

Physical Characterization of Maize Grits Expanded Snacks and Changes in the Carotenoid Profile

The objective of this work was to evaluate the effects of feed moisture (13-17%, wb) and barrel temperature (120-160 °C) on physicochemical properties, and changes in the carotenoid profile of maize grits extruded snacks. The extrudates were obtained in a single-screw extruder, according to a 3² factorial design with two replicates. The linear coefficients of feed moisture and barrel temperature mainly affected the physicochemical properties. On the other hand, the interaction coefficient β₁₁₂ dominated the change in total carotenoids, lutein, zeaxanthin, and β-carotene. The quadratic coefficients were also important for changes in total color (regarding feed moisture), and for β-cryptoxanthin, specific mechanical energy, and volumetric expansion index (regarding barrel temperature). β-cryptoxanthin and β-carotene increased, whereas lutein and zeaxanthin decreased. The mathematical models developed from responses revealed two feasible operating regions under the domain explored. For a satisfactory process, from a technological and nutritional point of view, it is suggested to extrude at the operating conditions ranging between 13.2-13.7% feed moisture and 120-132 °C barrel temperature. Under these conditions, the specific mechanical energy input required was 410-450 kJ/kg, and extrudates with a volumetric expansion index greater than 12, a crispness work less than 0.4 N.mm, and with moderate increments in the levels of β-carotene and β-cryptoxanthin were produced. The use of richer cultivars in carotenoids could contribute to the production of healthier snacks.

Influence of osmotic pretreatments on the quality properties of deep-fat fried green plantain

Modification of the surface properties of materials is a promising approach to reduce the uptake of oils during frying. In this work, the quality characteristics of plantain chips subjected to a pretreatment consisting of osmotic drying in sugar solutions (29 and 45° Brix; 40 and 80 °C) were evaluated. True density, apparent density, porosity and moisture content were measured in pretreated samples (PS) before frying. Image ESEM was used to evaluate microstructural changes on the surface and in cross-sections at different depths. Global oil absorption (GOA) and fatty acid profile were monitored in surface and deep cross-sections (DCS). The color parameters of chips (L*, a*, b*, ΔE), browning index, crispness, crunchiness and hardness were evaluated during frying. Oil absorption in the crust was lower in samples subjected to pretreatments with a higher temperature. PS showed high gelatinization in both the surface and DCS, thus changing crust physical properties, total oil uptake and fatty acid profile. An exponential correlation between porosity (ε) and GOA was found, while a second order correlation was found between ε and the fatty acid profile. The characteristics of texture and color, as desired by the consumer, were reached more quickly in the PS at 29° Brix and 40 °C.