No abstract

A mixture of orange vesicle flour, commercial nixtamalized corn flour and potato starch was extruded using a Brabender Laboratory single screw extruder (2:1 L/D). The resulting pellets were expanded by microwaves. Expansion index, bulk density, penetration force, carotenoid content, and dietary fiber were measured for this third-generation snack and optimum production conditions were estimated. Response surface methodology was applied using a central composite rotatable experimental design to evaluate the effect of moisture content and extrusion temperature. Temperature mainly affected the expansion index, bulk density and penetration force, while carotenoids content was affected by moisture content. Surface overlap was used to identify optimum processing conditions: temperature: 128-130°C; moisture content: 22-24 %. Insoluble dietary fiber decreased and soluble dietary fiber increased after extrusion.

The aim of this work was to study the effects of barrel temperature (BT, 93.5–140.5°C), feed moisture (FM, 21.3–34.7%), and winter squash flour content (SFC, 0.43–15.6%) on physicochemical properties of microwave‐expanded third‐generation snack foods obtained by extrusion. Physicochemical properties used for optimization were expansion index (EI), penetration force (PF), specific mechanical energy (SME), and total color difference (ΔE). Response surface methodology was used for the analysis of data. The highest values of EI and lowest values of PF were found at high BT and low FM. The lowest values of SME were obtained at high levels of FM throughout the range of BT and SFC, whereas the highest values of ΔE were obtained at high SFC and low FM. Increasing levels of SFC increased ΔE values, whereas EI and SME values decreased. The best processing conditions (EI > 6.0, PF < 9.5 N, SME < 172 kJ/kg, and ΔE < 18) were found in the range of BT, 122–141°C; FM, 24.7–29.5%; and SFC, 0–10.9%. Under optimal process conditions, the retention of total carotenoids was higher than 60%. It is possible to manufacture third‐generation snack foods with good physicochemical properties, which could bring a health benefit because of the presence of carotenoids and dietary fiber in winter squash flour.

Tomato (Solanum lycopersicum) fruit is susceptible to chilling injury (CI), a physiological disorder caused by low, non-freezing temperatures that affects fruit postharvest quality. Little is known about the biochemical basis of CI, and the aim of this study was to identify proteins related to this disorder in ‘Imperial’ tomato fruit. CI and protein expression changes were analyzed during fruit ripening (0, 4, 8, and 12 days at 21 °C) after storage under chilling (5 °C) and non-chilling conditions (21 °C) for 5, 15, and 25 days. The main CI symptoms observed were uneven fruit ripening and color development, pitting, and decay. Protein analysis of two-dimensional gels showed that 6% of the detected spots (≈300) changed their expression in response to cold. The identified proteins are involved in carbon metabolism, oxidative stress, photosynthesis, and protein processing and degradation; two were related to cold stress, showing higher accumulation in non-damaged tissue of chilled fruit: thioredoxin peroxidase (TPxI) and glycine-rich RNA-binding protein (GR-RBP). This is the first report suggesting an important role for TPxI and GR-RBP in cold response during tomato fruit ripening, and they may be acting through redox sensing and regulation of gene expression at low temperature. These enzymes and the other chilling-related proteins might be working together to maintain the cellular homeostasis under cold stress conditions.

Waxed and nonwaxed mature green tomato fruits were stored at 12C (nonchilled) or 5C (chilled) for 5, 10, 15 and 20 days before being transferred to 22C for 3, 6, 9 and 12 days, were evaluated for weight loss, chemical composition, skin color, chilling injury (CI) index and pigment content. Waxed fruits showed a delay in weight loss, color development and ripening. The sensitivity of tomato fruit to CI was reduced in waxed fruits, which showed a delay in the appearance of symptoms. A delay in chlorophyll degradation and lycopene synthesis was observed as a result of the use of wax and low temperature. Waxing of tomato fruits allowed their storage at temperatures below critical reducing CI sensitivity and maintaining quality giving more time for marketing. PRACTICAL APPLICATIONS Nowadays, local tomato producers use wax on fruits as an everyday practice to carry postharvest fungicides and to improve brightness. They store tomato fruits at nonchilling temperature (12C) because lower temperatures would cause chilling injury and irregular ripening. In this way, it is interesting that waxing tomato fruits allow reducing their storage temperature, protecting them from chilling injury and maintaining their quality and correct color change and ripening; thereby producers and sellers have more days to position their fruits with no extra cost.