A natural whitening alternative from upcycled food waste (acid whey) and underutilized grains (millet)

Abstract

The dairy industry faces a daunting challenge in managing acid whey (AW), a byproduct of Greek yogurt manufacturing that is costly to dispose of and challenging to incorporate into other food products. However, recent studies have demonstrated that AW can be transformed into a viable white powder by encapsulating it in millet flour. Recently, concerns over the safety of the commonly used food-grade whitener titanium dioxide (TiO₂) have arisen, and the search for an alternative food-whitening agent has become essential. This study evaluated the color attribute, proximate composition, sugar profile, amino acid profile, total phenolic content, antioxidant activity, and antinutrient content of the novel acid whey millet (AWM) powder. The L* values of the AWM powders were significantly higher than TiO₂ and the rest of the millet formulations. The crude protein content in the AWM powders was significantly (p < 0.05) lower when compared to the crude protein content in millet flours. AWM powders had higher lactose levels and retained all major amino acids after spray drying. Macrominerals (P, K, Ca, and Na) and microminerals (Zn and Cu) significantly increased in the AWM powder, while tannin content was reduced in AWM powders. These findings suggest that AWM powder is a white powder that contains a wide range of components with high nutritional value that could be readily incorporated into various applications. In summary, this study provides a valuable contribution to the dairy industry by highlighting the potential of AWM powders as a natural alternative food whitening agent to TiO₂.

Figure 1

Overall summary of novel white powders and potential industrial applications contributing to sustainable food systems.

Figure 2

(a) millet flour and spray dried samples compared to TiO₂ (b) Lightness (L*) and (c) witnesses index values of the samples. Mean values followed by a different letter are significantly different. Legend: Image, L*, and whiteness index values of the flour and powder samples. BY: plain Barnyard millet flour; LT: plain Little millet flour; SD_BY: spray dried Barnyard millet soluble fraction; SD_LT: spray dried Little millet soluble fraction; BAW: 25% w/v Barnyard millet + acid whey; LAW: 25% w/v Little millet + acid whey.

Figure 3

Proximate analysis of millet flours and acid whey millet powders (a) carbohydrate (b) crude protein (c) moisture (d) crude fat (e) crude fiber (f) ash. Mean values followed by different letters are significantly different (p < 0.05). Legend: Proximate analysis of powder samples. BY: plain Barnyard millet flour; LT: plain Little millet flour; SD_BY: spray dried Barnyard millet soluble fraction; SD_LT: spray dried Little millet soluble fraction; BAW: 25% w/v Barnyard millet + acid whey; LAW: 25% w/v Little millet + acid whey.

Figure 4

Amino acid profile of AWM sample and millet flour samples compared to popular cereal grains. W/W% = grams per 100 g of sample. The data for maize, wheat, and rice was obtained from Chandra et al.. Mean values followed by a different letter are significantly different. Legend: Amino acid profile of powder samples. BY: plain Barnyard millet flour; LT: plain Little millet flour; SD_BY: spray dried Barnyard millet soluble fraction; SD_LT: spray dried Little millet soluble fraction; BAW: 25% w/v Barnyard millet + acid whey; LAW: 25% w/v Little millet + acid whey.

Figure 5

Mineral profile of acid whey millet powders and millet flours (a) macronutrients (b) micronutrients. The data for maize, wheat, and rice was obtained from Chandra et al.. Legend: Mineral content in the powder samples .BY: plain Barnyard millet flour; LT: plain Little millet flour; SD_BY: spray dried Barnyard millet soluble fraction; SD_LT: spray dried Little millet soluble fraction; BAW: 25% w/v Barnyard millet + acid whey; LAW: 25% w/v Little millet + acid whey.

Figure 6

Antioxidant and antinutritional properties of AWM powders and millet flour (a) Total phenol content (b) Gallic acid calibration curve (c) TBARS concentration (d) MDA calibration curve (e) Tannin content (f) Catechin calibration curve (g) DPPH activity. Significant differences among samples are expressed by different lowercase letters. Legend: Antioxidant and antinutritional properties of the powder samples. BY: plain Barnyard millet flour; LT: plain Little millet flour; SD_BY: spray dried Barnyard millet soluble fraction; SD_LT: spray dried Little millet soluble fraction; BAW: 25% w/v Barnyard millet + acid whey; LAW: 25% w/v Little millet + acid whey.

Figure 7

(a) Potential applications of novel millet acid whey powder. (b) Demonstrates the potential research impacts of producing AWM powder, based on assumptions derived from in-house laboratory experiments.