Deliquescence Behavior and Chemical Stability of Vitamin C Forms (Ascorbic Acid, Sodium Ascorbate, and Calcium Ascorbate) and Blends

Figures & data

Figure 1 Moisture sorption isotherms for single and binary mixtures of vitamin C forms. A. Sorption isotherms for single vitamins forms. Isotherms for each ingredient are shown by:

Ascorbic acid

DHAA

Ca Ascorbate

Na Ascorbate

Ascorbyl palmitate. B. Sorption isotherms for binary mixtures of vitamin forms. Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate, P = ascorbyl palmitate. Isotherms for each mixture are shown by:

AN

AC

AP

NC

NP

CP.

Figure 2 Moisture sorption isotherms for a single, binary, ternary, and quaternary mixture containing sodium ascorbate. Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate, P = ascorbyl palmitate. Isotherms for each mixture are shown by:

N

AN

ANC

ANCP.

Table 1 Water activity, pH, deliquescence point, and solubility information for ingredients and their mixtures at 25°C

Sample composition ^a	pH	Vitamin solubility value (mol/kg) ^f	RH0 or RH0mix (%), observed	aw × 100	RH0mix (%), predicted^b	χ ^c
Ascorbic acid (A)	1.41	1.89	— ^d	98
Sodium ascorbate (Na)	7.58	3.13	86	86
Calcium ascorbate (Ca)	6.92	1.03	— ^d	94
Ascorbyl palmitate (P) ^e	5.75	0.014
Dehydroascorbic acid (D)	2.23		—^d	95
ANa	5.75		82	82	84	0.97
ACa	4.25		92	92	92	1.00
AP	2.76		— ^d	97
NaCa	7.49		87	85	81	1.05
NaP	6.51		84	83
CaP	5.34		— ^d	93
50:50 D:Na			78		82	0.95
ANaCa	5.66		81	81	76	1.07
ANaCaP	5.56		83	82	76	1.09
^aAll mixtures are equimass for each vitamin C form.
^bRH0mix was predicted by the Ross equation: (aw)mix = (aw)1 * (aw)2 * (aw)i.
^cχ = aw(observed)/(a°w)1(a°w)2.
^dAbove moisture sorption balance RH range (above 94% RH).
^eNot a deliquescent ingredient.
^fValues for solubility of the difference vitamin C forms are taken from the following references: Windholz, 1983 (A and Na); Mishelevich and Apelblat, 2008 (Ca); Swern, 1949 (P).

Figure 3 Moisture sorption isotherms for individual DHAA and sodium ascorbate and binary mixtures of the two in ratios of 50:50, 25:75, and 10:90 DHAA:N. Individual ingredients are abbreviated as: N = sodium ascorbate, D = dehydroascorbic acid. Isotherms for individual ingredients and mixtures are shown by:

D

N

50:50 DN

25:75 DN

10:90 DN.

Figure 4 Weight gain (%) for individual vitamin C forms and their binary mixtures during storage up to 12 weeks at 98% RH. A. Weight gain (%) for individual vitamin C forms over time. Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate, P = ascorbyl palmitate. Percent weight gain for individual ingredients is shown by:

A

.N

C

PB. Weight gain (%) for binary mixtures of vitamin C forms over time. Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate, P = ascorbyl palmitate. Percent weight gain for mixtures is shown by:

AN

AC

AP NC

NP

CP

Figure 5 Experimental and predicted moisture sorption isotherms for a ternary mixture of vitamin C forms (ANC). Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate. Sorption isotherms are shown by:

Experimental

Predicted.

Figure 6 Weight gain (%) for individual DHAA and binary mixtures of DHAA and sodium ascorbate in ratios of 50:50, 25:75, and 10:90 DHAA:N over time during storage at 98% RH. Individual ingredients are abbreviated as: N = sodium ascorbate, D = dehydroascorbic acid. Percent weight gain for mixtures is shown by:

D

50:50 DN

25:75 DN

. 10:90 DN

Figure 7 Vitamin C stability for individual vitamin forms and their binary mixtures during storage up to 12 weeks at 98% RH. A. Percent vitamin C remaining over time for different vitamin forms. Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate. Percent vitamin C remaining for individual vitamins is shown by:

A

N

C B. Percent vitamin C remaining over time for binary mixtures. Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate, P = ascorbyl palmitate. Percent vitamin C remaining for mixtures is shown by:

AN

AC

NC

AP

NP

CP.

Table 2 Endpoint vitamin C degradation after 12 weeks of storage at select RHs for individual vitamin C forms and in vitamin C ingredient mixtures. Results are reported as % degradation with standard deviations and different letters indicate significant differences^a. Each formulation was stored at three RHs selected to be above, near, and below the deliquescence point of the blend

	Storage % RH
Formulation ^b	98	89	85	75	54
A	9.6 ± 4.8 ^hijk				5.4 ± 5.5^hijk
Na	98.7 ± 1.8^ab		100.0 ± 0.0 ^a		1.98 ± 2.5^jk
Ca	100.0 ± 0.2 ^a				0.94 ± 1.6^jk
ANa	87.5 ± 4.7^abc		61.5 ± 9.6^def		0.98 ± 1.7^jk
ACa	74.8 ± 19.4^abcd	39.5 ± 11.0^fg			2.31± 4.0^jk
AP	15.4 ± 5.0^jk				3.43 ± 5.9^jk
NaCa	58.8 ± 7.9^fg		48.9 ± 17.5^efg		0.0 ± 0.0^k
NaP	100.0 ± 0.0 ^a		100.0 ± 0.0 ^a		11.7 ± 12.8^hijk
CaP	100.0 ± 0.0 ^a	39.0 ± 5.5^fg			7.0 ± 6.1^hijk
ANaCa	68.0 ± 8.0^cde		63.2 ± 11.8^cdef	8.2 ± 7.7^hijk	10.6 ± 11.0^hijk
ANaCaP	100.0 ± 0.0 ^a		100.0 ± 0.0^a		3.8± 6.6^ijk
D	100.0 ± 0.0 ^a		100.0 ± 0.0 ^a		9.1 ± 0.0 ^a
50:50 DNa	100.0 ± 0.0 ^a			86.0 ± 2.3^bcde	44.3 ± 23.1^gh
25:75 DNa	100.0 ± 0.0 ^a			37.3 ± 6.3^ghij	15.3 ± 10.2^ghi
10:90 DNa	100.0 ± 0.0 ^a			28.6 ± 6.5^ghijk	5.6 ± 9.8^jk
^aSamples with different letters had significantly different degradation of that vitamin C form compared to all other formulations.
^bLetters listed in formulations indicate the following ingredients: A = ascorbic acid; Na = sodium ascorbate; Ca = calcium ascorbate; P = ascorbyl palmitate; D = dehydroascorbic acid.

Figure 8 Percent of reduced ascorbate remaining over time for binary mixtures of dehydroascorbic acid and sodium ascorbate in ratios of 50:50, 25:75, or 10:90 DHAA:N stored at 98% RH. Individual ingredients are abbreviated as: N = sodium ascorbate, D = dehydroascorbic acid. Percent reduced ascorbate remaining in mixtures is shown by:

50:50 DN

25:75 DN

10:90 DN.

Figure 9 Percent weight gain versus % vitamin C remaining for vitamin C forms and their blends stored at 98% RH and 25°C up to 12 weeks. A. Percent weight gain versus % vitamin C remaining for individual vitamin C forms. Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate. Trends for individual vitamins are shown by:

N

A

C. B. Percent weight gain versus % vitamin C remaining for blends of vitamin C forms. Individual ingredients are abbreviated as: A = ascorbic acid, N = sodium ascorbate, C = calcium ascorbate. Trends for vitamin C blends are shown by:

AN

AC

NC

AP

NP

CP

ANC

ANCP.

Windholz , M. 1983 . The Merck Index an Encyclopedia of Chemicals, Drugs, and Biologicals , 10th , Merck, NJ : Rahway .

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