Monitoring retrogradation in liquorice-type sweets of different size and hardness

Four different liquorice-type sweets (LTS) were compared: LS: long stick (253 mm length x 9 mm diameter) + soft recipe (3% w/w acetylated starch; 49/21 w/w sugar/glucose syrup ratio); LH: long stick + hard recipe (6%; 24/42); SS: short stick (115 x 5 mm) + soft recipe; SH: short stick + hard recipe. The length values were used to establish short-term retrogradation kinetics using Avrami's crystallisation model. The subsequent hardness (48 h) was checked. The retrogradation was faster in the hard recipes. The shortening kinetics could be explained by Avrami's model. The equations Log [-Ln theta] vs. Log (t) used to calculate the constants of retrogradation (k) and Avrami's coefficients (n) presented R-2 values of between 0.98 and 0.99. The mean k.10(3) (min(-n)) values were: SH (111.5) > LS (110.9) > LH (97.3) > SS (92.2), while the mean n values were: LH (0.722) > SH (0.680) > SS (0.669) > LS (0.537). Differences in hardness between recipes were only detected (p < 0.05) in long sticks, which showed more pronounced differences in the retrogradation rate. This suggests that the rate of retrogradation could be related with subsequent LTS hardness. Thus, the on-line control of shortening is proposed for monitoring the rate of retrogradation in LTS.