Design-Driven Optimisation of Brine Blanching for Quality Improvement in Freeze-Dried Shrimp Bites

Abstract

This study optimised brine blanching conditions to produce freeze-dried shrimp bites from Parapenaeopsis stylifera using a multilevel factorial design. The effects of brine concentration (1%, 2%, 3% w/v) and blanching duration (1, 3, 5, and 7 min) at 90 °C were assessed on physicochemical, sensory, and structural quality attributes, including blanching loss, sensory acceptability, rehydration ratio, water activity, colour parameters, salt content, astaxanthin content, and texture properties. Both processing variables significantly affected most measured quality attributes, although the magnitude and significance of the main and interaction effects varied across responses. Short-time, low-salt treatments (1–3 min, 1–2% brine) yielded the highest sensory acceptability and rehydration capacity, while effectively preserving colour and texture. Multi-response optimisation identified 3 minutes of blanching at 2% brine concentration as optimal, achieving a composite desirability of 0.511. In contrast, extended treatments (5–7 min, 3% brine) enhanced preservation traits by lowering water activity and improving astaxanthin content, but reduced sensory appeal and rehydration performance. Colour analysis showed that minimal processing better maintained lightness, whereas longer treatments intensified red–yellow pigmentation due to controlled carotenoid release. Texture firmness increased progressively with processing intensity, likely due to enhanced formation of the protein gel network. Overall, the study shows how brine concentration and blanching time can be adjusted to achieve a suitable balance among the physicochemical, textural, rehydration, and sensory properties of freeze-dried shrimp bites.