Frozen State Transitions in Freeze-Concentrated Lactose-Protein-Cornstarch Systems

Figures & data

Figure 1 DSC thermograms (Second scan) of 20% freeze-dried anhydrous, lactose, lactose/albumin (1:1), lactose/gelatin (1:1), lactose/cornstarch (1:1), and lactose/gelatin/cornstarch (1:1:1). The arrow indicates the onset of T_g.

Figure 2 State diagrams for lactose, lactose/albumin (1:1), lactose/gelatin (1:1), lactose/cornstarch, and lactose/cornstarch/gelatin (1:1:1). T_g curve predicted by the Gordon and Taylor equation (Gordon and Taylor, 1952). Below T_g all solutions are in the glassy state. Maximally freeze concentrated solutions show constant T_g′ (onset of glass transition) and T_m′ (onset ice melting temperature) values. The T_m′ of solutions was at the endpoint region of T_g′. All solution show maximum concentration of unfrozen phase at C_g′.

Table 1 Anhydrous onset of glass transition temperature (T_g) as well as onset of glass transition temperature (T_g′), onset of ice melting temperature (T_m′), and solute concentration value (C_g′) of maximally freeze-concentrated solutions of lactose, lactose protein, and lactose cornstarch mixtures. A 15 minute annealing time was used for all solutions

Material	Annealing temperature (°C)	Tg (°C) ^a (onset) (°C)	Tg′ (°C ) ^a (onset) (°C)	Tm′ (°C ) ^a (onset) (°C)	k ^a	Cg′ ^b ^(%)
Lactose	−31	105 ± 1 ^a	−41 ± 1 ^a	−31 ± 1 ^a	6.5	82
Lactose/albumin (1:1)	−28	113 ± 2 ^b	−48 ± 1 ^b	−28 ± 1 ^b	6.4	78
Lactose/gelatine (1:1)	−27	117± 1 ^a	−53 ± 1 ^a	−25 ± 1 ^a	6.6	78
Lactose/cornstarch (1:1)	−24	123± 1^d	−47 ± 1 ^b	−23 ± 1^d	6.5	78
Lactose/gelatine/ cornstarch (1:1:1)	−26	140 ± 1 ^a	−49 ± 1 ^b	−24 ± 1 ^a	5.5	75
^aConstant k for eq. (1); ^bCalculated using eq. (1).

Figure 3 Thermograms of 20%, lactose, lactose/albumin (1:1), lactose/gelatin (1:1), lactose/cornstarch (1:1), and lactose/gelatin/cornstarch (1:1:1) solutions isothermally annealed for 15 minutes before determination of the transitions during rewarming from −100 to 20°C at 5°C min⁻¹.