Technical Yearbook 2024

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characteristics of the particles, a high percentage of the product will carry out its effect in suspension. Figure 1 shows the suspension of the two plant-based proteins at pH 3.5. Figure 2 shows results from SDS-PAGE electrophoresis of potato and pea proteins. Potato protein is characterised by a predominant band corresponding to about 40 KDa (patatin), while pea protein consists of many protein fragments distributed in the 10 - 100 KDa range. Evaluating the oenological performance of plant proteins The effects of pea and potato proteins on wine were evaluated by monitoring the following aspects: clarifying efficacy, oxidation management, astringency reduction, effect on colloidal instability and sensory impact. Generally, the suggested dosages of pea and potato proteins in winemaking vary between 5 and 30 g/hL depending on the time of application and the intended objective. Oenological trials were performed by standardising the dosage to 10 g/hL except flotation, where the dosage applied was 5 g/ hL. Clarifying efficacy Figure 3 shows that the molecular mass of plant-based proteins influences their clarifying ability. Controlled hydrolysis can increase the clarifying ability of these proteins. As a comparative example, gelatine with a low degree of hydrolysis (100 Bloom degrees) clarified Trebbiano wine to 5 NTU and Sagrantino wine to 2 NTU (data not shown). Figure 4 shows the clarifying ability of potato proteins with different degrees of hydrolysis in two wines. The treated wine samples

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FIGURE 4. Turbidity 48 hours after the addition of products in Sauvignon blanc wine with pH 3.3 and Trebbiano wine with pH 3.2. A – Sauvignon blanc control, B – pea protein, C – pea protein moderate hydrolysis, D – Trebbiano control, E – potato protein, F – potato protein moderate hydrolysis. FIGURE 4. Turbidity 48 hours after the addition of products in Sauvignon blanc wine with pH 3.3 and Trebbiano wine with pH 3.2. A – Sauvignon blanc control, B – pea protein, C – pea protein moderate hydrolysis, D – Trebbiano control, E – potato protein, F – potato protein moderate hydrolysis. Oxidation management Pea proteins are better suited than potato proteins for reducing browning. This effect can be monitored by measuring the decrease in optical density at the wavelength of 420 nm, as shown in Figure 5. In this case, protein size does not seem to influence this property. Pea proteins are also found to be the best in reducing the concentration of iron, a metal with an oxidation catalyst effect, as shown in Figure 6. FIGURE 4. Turbidity 48 hours after the addition of products in Sauvignon blanc wine with pH 3.3 and Trebbiano wine with pH 3.2. A – Sauvignon blanc control, B – pea protein, C – pea protein moderate hydrolysis, D – Trebbiano control, E – potato protein, F – potato protein moderate hydrolysis. Oxidation management Pea proteins are better suited than potato proteins for reducing browning. This effect can be monitored by measuring the decrease in optical density at the wavelength of 420 nm, as shown in Figure 5. In this case, protein size does not seem to influence this property. Pea proteins are also found to be the best in reducing the concentration of iron, a metal with an oxidation catalyst effect, as shown in Figure 6.

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D.O. 420 nm

CONTROL

PEA PROTEIN

POTATO PROTEIN

TREBBIANO SAUVIGNON BIANCO ZIBIBBO

D.O. 420 nm

FIGURE 5. Average optical density reading at 420 nm following clarification with pea and potato proteins. FIGURE 5. Average optical density reading at 420 nm following clarification with pea and potato proteins.

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FIGURE 5. Average optical density reading at 420 nm following clarification with pea and potato proteins.

% REDUCTION [FE]

were purposely photographed in front of a background with

PEA PROTEIN

POTATO PROTEIN

PVI/PVP

horizontal black lines to make the difference in turbidity obtained more visible.

102 Potato proteins react better with astringent tannins than pea proteins. Clarification tests performed on different wines confirmed this effect, as shown in Figure 7. The performance of hydrolysed gelatine is shown for comparison. TECHNICAL YEARBOOK 2024 FIGURE 6. Percentage reduction in average iron concentration obtained from clarifications performed on different types of wines with pea and potato proteins. The performance of PVI/PVP is shown in comparison. Reduction of astringency FIGURE 6. Percentage reduction in average iron concentration obtained from clarifications performed on different types of wines with pea and potato proteins. The performance of PVI/PVP is shown in comparison.