Effects of concentration by block freezing and vacuum evaporation on the physicochemical properties and digestibility of whey

Figures & data

Figure 1. Evolution of the solids content (°brix) in the concentrate and of the ice fraction as a function of the cryoconcentration cycles.

Table 1. Physicochemical parameters of fresh, evaporated, concentrated and their ice fractions whey.

	TSS	ρ	Acidity	Protein	Lactose
Samples	(g/100 g)	(g/m^3)	(g lactic acid/L)	(g/100 g)	(g/100 g)
Fresh whey	6.12 ± 0.03^a	1.17 ± 0.11^a	1.11 ± 0.02^a	0.89 ± 0.02^b	3.78 ± 0.02^c
Evaporated	15.60 ± 0.10^b	1.25 ± 0.06^ab	1.13 ± 0.03^ab	2.24 ± 0.006^d	7.22 ± 0.69^e
Cryoconcentrated cycle 1	15.60 ± 0.18^b	1.31 ± 0.09^ab	1.15 ± 0.01^b	1.73 ± 0.03^c	6.18 ± 0.09^d
Ice cycle 1	3.52 ± 0.07^b	0.89 ± 0.01^b	1.01 ± 0.04^b	0.36 ± 0.004^a	0.23 ± 0.02^a
Cryoconcentrated cycle 2	21.50 ± 0.15^c	1.43 ± 0.12^bc	1.19 ± 0.02^c	3.05 ± 0.04^e	8.19 ± 0.46^f
Ice cycle 2	8.10 ± 0.15^c	1.19 ± 0.02^a	1.13 ± 0.05 ^a	0.46 ± 0.01^a	1.17 ± 0.05^b
Cryoconcentrated cycle 3	30.00 ± 0.09 ^d	1.67 ± 0.02 ^d	1.25 ± 0.01^d	3.22 ± 0.23^e	7.65 ± 0.54^e,f
Ice cycle 3	13.69 ± 0.08^d	1.30 ± 0.06^ac	1.18 ± 0.03^ab	0.91 ± 0.06^b	3.96 ± 0.37^c

Data are expressed as mean values ± SD. Different lowercase letters in the same column indicate significant differences between samples (p < .05).

Table 2. Proximal composition of fresh, evaporated and cryoconcentrated cycle 3 whey.

Samples	Fresh whey	Evaporated	Cryoconcentrated cycle 3
Protein (g/100 g)	0.89 ± 0.02^a	2.24 ± 0.006^b	3.22 ± 0.23^c
Fat (g/100 g)	0.24 ± 0.03^a	0.97 ± 0.02^b	0.16 ± 0.02^a
Carbohydrates (g/100 g)	4.70 ± 0.05^a	21.32 ± 2.15^c	13.02 ± 1.02^b
Humidity (g/100 g)	92.64 ± 0.03^c	69.62 ± 0.92^a	77.32 ± 0.27^b
Ash (g/100 g)	1.53 ± 0.02^a	6.52 ± 0.07^c	6.25 ± 0.03^b

Data are expressed as mean values ± SD. Different lowercase letters in the same row indicate significant differences between samples (p < .05).

Table 3. Amino acid content of fresh, evaporated and cryoconcentrated cycle 3 whey.

Amino acid (g/100 g)	Fresh whey	Evaporated	Cryoconcentrated cycle 1	Cryoconcentrated cycle 2	Cryoconcentrated cycle 3
Asp	0.07 ± 0.002^a	0.10 ± 0.001^b	0.09 ± 0.001^b	0.13 ± 0.001^c	0.20 ± 0.001^d
Glu	0.08 ± 0.001^a	0.12 ± 0.002^b	0.11 ± 0.001^b	0.17 ± 0.002^c	0.22 ± 0.001^d
Ser	0.05 ± 0.000^a	0.08 ± 0.001^b	0.08 ± 0.001^b	0.11 ± 0.001^c	0.16 ± 0.001^d
Gly	0.04 ± 0.001^a	0.06 ± 0.001^b	0.07 ± 0.001^b	0.09 ± 0.001^bc	0.11 ± 0.001^c
Hys	0.08 ± 0.001^a	0.12 ± 0.002^b	0.10 ± 0.001^ab	0.15 ± 0.002^bc	0.23 ± 0.004^d
Arg	0.09 ± 0.002^a	0.14 ± 0.005^b	0.14 ± 0.003^b	0.18 ± 0.004^c	0.26 ± 0.006^d
Thr	0.06 ± 0.001^a	0.09 ± 0.001^b	0.08 ± 0.001^ab	0.12 ± 0.002^c	0.18 ± 0.003^d
Ala	0.05 ± 0.001^a	0.07 ± 0.003^b	0.06 ± 0.002^ab	0.10 ± 0.002^c	0.14 ± 0.004^d
Pro	0.06 ± 0.002^a	0.09 ± 0.003^b	0.10 ± 0.002^b	0.13 ± 0.003^bc	0.18 ± 0.001^d
Tyr	0.09 ± 0.001^a	0.14 ± 0.005^b	0.16 ± 0.002^b	0.20 ± 0.001^c	0.27 ± 0.008^d
Val	0.06 ± 0.002^a	0.09 ± 0.001^b	0.10 ± 0.001^b	0.14 ± 0.002^c	0.18 ± 0.002^d
Met	0.08 ± 0.001^a	0.12 ± 0.003^b	0.12 ± 0.002^b	0.19 ± 0.003^c	0.23 ± 0.003^d
Cys	<0.02	<0.02	<0.02	<0.02	<0.02
Ile	0.07 ± 0.001^a	0.10 ± 0.002^b	0.12 ± 0.002^b	0.16 ± 0.003^c	0.20 ± 0.002^d
Leu	0.07 ± 0.002^a	0.10 ± 0.001^b	0.11 ± 0.001^b	0.16 ± 0.002^c	0.20 ± 0.001^d
Phe	0.09 ± 0.003^a	0.13 ± 0.006^b	0.13 ± 0.002^b	0.19 ± 0.003^c	0.25 ± 0.004^d
Lys	0.08 ± 0.000^a	0.12 ± 0.001^b	0.09 ± 0.001^a	0.16 ± 0.002^c	0.22 ± 0.002^d

Data are expressed as mean values ± SD. Different lowercase letters in the same row indicate significant differencesbetween samples (p < .05).

Figure 2. FT-IR spectra of protein secondary structure in fresh, evaporated and cryoconcentrated whey.

Table 4. Percentages of protein secondary structure of fresh, evaporated and cryoconcentrated cycle 3 whey.

Protein secondary structure (%)	Wavenumber (cm^−1)	Fresh whey	Evaporated	Cryoconcentrated cycle 3
β-sheet Intermolecular	1618–1621	8.96 ± 1.12^b	0.56 ± 0.02^a	8.54 ± 1.02^b
β-sheet Intramolecular	1625–1636	3.22 ± 0.52^a	49.36 ± 3.51^c	4.27 ± 0.98^b
α-helix	1651–1652	48.39 ± 2.61^c	28.20 ± 1.23^a	42.73 ± 1.98^b
β -Turns	1669	3.58 ± 0.68^c	0.70 ± 0.02^a	1.71 ± 0.11^b
β-sheet anti-parallel intramolecular	1683	17.92 ± 2.15^b	7.05 ± 0.68^a	17.09 ± 1.18^b
β-sheet anti-parallel	1701	17.92 ± 1.54^b	14.10 ± 1.35^a	25.64 ± 2.14^c

Data are expressed as mean values ± SD. Different lowercase letters in the same row indicate significant differences between samples (p < 0.05).

Figure 3. Degree of hydrolysis of fresh, evaporated and cryoconcentrated cycle 3 whey. (a) gastric process; (b) intestinal process.