Abstract:
The purpose of this research was to examine the feasibility of carbon dioxide (CO2)
laser perforation and its potential utilization as a novel skin pretreatment for the
sugar infusion process of IQF (individually quick frozen) blueberries. In the first
study, IQF blueberries were treated with varying degrees of laser perforation (i.e., 3
levels of perforation density x 3 levels of perforation depth = 9 treatment
combinations) and then subjected to stepwise sugar infusion using low solution
concentration increments (5 °Brix/day) to a final °Brix of 70 with a high fructose
corn syrup (HFCS) solution. The effects of the perforation density: depth
combinations were evaluated against a traditional mechanical treatment in terms of
fruit weight change and final product characteristics. A clear, systematic tendency of
increasing final fruit weight was observed as the two perforation parameters were
increased. The increase in the two parameters also contributed to producing infused
blueberries that were maintaining the original shape and appearance with reduced
product shrinkage and texture hardening as a result of enhanced solute impregnation.
Due to the invasive nature of the treatment, blueberries that were subjected to the
mechanical treatment showed considerable rupture at the end of the infusion process.
The second study was carried out under a sugar infusion condition using higher
solution concentration increments (10, 20 and 30 °Brix/day). Due to the increased
osmotic gradient, the time required for the fruit to reach the target soluble solid
content (70 ± 0.5 °Brix) was markedly shortened. A systematic increase in the final
fruit weight with increasing perforation density and depth was again observed.
However, only the fruit that was subjected to the greatest laser perforation exhibited
promoted solute gain, thereby attaining a moderate final process yield with reduced
product shrinkage. Overall, the results of the two studies demonstrate the ability of
CO₂ laser perforation as a non-contact, minimally invasive skin pretreatment for the
sugar infusion of frozen blueberries that significantly enhances solute impregnation,
leading to improved process yield, process efficiency, and final product quality.
