Air Naturel GOTA Ultrasonic Air Humidifier User Manual download pdf (Page 49)

IV Congreso Internacional de Ciencia y Tecnología de Alimentos - Córdoba, Argentina 14 a 16 de Noviembre de 2012

showed the lowest 

as well as the lowest . GG-trehalose system had intermediate values. These results

show that the inhibition of trehalose crystallisation was achieved by both gums and especially by VG.

Figure 1: DSC thermograms of freeze dried trehalose systems with 0.1% w/v guar or vinal gums 0.1% (GG

and VG, respectively) or without gums equilibrated in DSC pans at 43 % RH for one day. Arrows show glass

transition (T

) and crystallisation and melting enthalpies values are indicated.

Table 1: Degree of total trehalose dihydrate crystallisation () and degree of trehalose dihydrate

crystallisation during humidification (

) of freeze dried trehalose systems with 0.1% w/v guar or vinal gums

(GG and VG, respectively) or without gums equilibrated in DSC pans at 43 % RH for one day.



trehalose

86.1

74.7

trehalose + GG

64.5

37.1

trehalose + VG

24.3

14.9

Freeze-dried lactose formulations humidified at 33% RH

Lactose samples (with or without gums) equilibrated at 33% HR have a T

value around 40°C. Lactose

crystallizes as monohydrate but the crystallisation of the anhydrous form is also possible. In both cases, the

water content of the systems at 33% RH allows lactose crystallisation when the temperature exceeds the T

Then, isothermal DSC runs were conducted at several temperatures between 50 and 65°C in order to evaluate

lactose crystallisation. As an example of the obtained thermograms, Figure 2 shows those obtained at 55°C.

Earlier and sharper peaks related to lactose crystallisation appeared in lactose-gum termograms. GG-lactose

system showed the earliest and smaller exothermic peak. The VG-lactose system presented a peak at

intermediate times between lactose and GG-lactose systems. The shape of the peak and the crystallisation

enthalpy for the systems containing VG and GG were similar between them. Instead, lactose system without

gum had wider peak of crystallisation for all the temperatures studied. This difference in shape for the

crystallisation peak could be related to a variation of the lactose crystallisation mechanism as a consequence

of the gum presence (Kedward et al, 1998). The same trend was obtained at 60 and 65°C for the three

systems (data not shown) respect to the thermograms showed in Figure 2. At 50°C, only the GG- lactose

system showed crystallisation during 130 minutes-DSC runs.

Figure 3a shows the crystallisation enthalpy as a function of temperature for all studied systems. Lactose

system showed the highest crystallisation enthalpies, which increased for higher temperatures. Both gum-

lactose systems had lower enthalpy values than lactose systems, with similar values between them, which

also remained steady when temperature was increased. The fact that the gum free system presented the

highest crystallisation enthalpy showed that lactose crystallisation thermodynamics is affected in the

presence of both gums.

Fig 3b shows the crystallisation time (the time difference between endset and onset crystallisation, or

induction time). The gum-free system showed the slowest lactose crystallisation rate at all analysed

temperatures. VG and GG systems showed shorter and similar crystallisation times, which decreased slightly

as increasing temperature of the isothermal run at DSC.

25 50 75 100

33.8 J/g

89.6 J/g

15.8 J/g

119.6 J/g

trehalose+ VG

trehalose+ GG

trehalose

2 W/g

crystallization

13.2 J/g

38.0 J/g

melting

Temperature (ºC)

Heat flow (W/g), exo >

1 2 ... 44 45 46 47 48 49 50 51 52 53 54 ... 327 328

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Air Naturel GOTA Ultrasonic Air Humidifier User Manual Page 49

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