Effects of a chitosan‐based coating with ascorbic acid on post‐harvest quality and core browning of ‘Yali’ pears (Pyrus bertschneideri Rehd.)

BACKGROUND: Chitosan (CTS), as an ideal coating material, has been used for post‐harvest treatment of fruits and vegetables. The effects of coating with 1.5% CTS, alone or combined with 10 mmol L^?1 ascorbic acid (AsA), on post‐harvest quality and core browning (CB) incidence in ‘Yali’ pears during storage at room temperature (25 ± 1 °C) were investigated in this study. RESULTS: It was found that both CTS coating and CTS + AsA coating delayed the increase of weight loss, retained greater firmness, total soluble solids and titratable acidity content than controls; coatings decreased respiration rate and membrane permeability, and also effectively inhibited CB after 60 days of storage. Compared with CTS coating alone, CTS + AsA coating increased these beneficial effects and also helped to retain a much higher AsA content and the activities of antioxidative enzymes (superoxide dismutase, catalase and ascorbate peroxidase). CONCLUSION: The CTS coating has the potential to maintain post‐harvest quality and control CB which is the main problem in ‘Yali’ pears during storage. The CTS + AsA coating has more effective application in this study, which could not only be due to reducing the respiration rate and inhibiting the senescence process, but also to increasing the antioxidant capability of the fruit. Copyright © 2008 Society of Chemical Industry     

Novel rotating die coupled to a twin-screw extruder as a new route to produce meat analogues with soy,pea and gluten

Modern plant-based meat analogues should have a pronounced fibrous structure as an important characteristic. In this study, we demonstrate that the combination of high moisture extrusion cooking (HMEC) with well-defined shear during cooling is a new process to make fibrous products using common meat analogue ingredients. The shear was applied via a cooling die attached to the extruder that was specially designed for that purpose. The in–house developed cooling die consists of two sequential rotating inner cylinders with a separate drive-unit in an outer cylinder that can be thermo-regulated. Three rotational speeds of the inner cylinder, 45, 75 and 105 min⁻¹, were tested for pea protein isolate, soy protein concentrate, vital wheat gluten and blends of pea or soy with gluten. A large effect on macro- and micro-texture and anisotropy index was found when the concentration of gluten was increased. The different ingredients and blends had different optimal conditions and reacted differently to the applied shear. Interestingly, the angle of the fibers observed in the samples differed at the different rotational speeds. This was attributed to the shear thinning behavior of the plant proteins and the velocity gradient in the rotating die, arising from the temperature and viscosity gradient. The ability to change the shear rate as an independent parameter in the rotating cooling die is unique and allows texture adjustments during processing. This is an important improvement for industrial HMEC and opens new product design possibilities.