A study investigated the potential of grape pomace as a novel ingredient for reformulating foods with less salt. The researchers found while the byproduct was successfully incorporated into tomato soup without significantly impacting consumer acceptance, the addition in vegetable juice was less desirable.
The team argued that the tomato soup with pomace may have been perceived more positively by consumers because soup was heated, leading to better solubility compared to the vegetable juice – a finding crucial for product developers as it indicates that incorporating grape pomace into heated formulations, such as soups or stews, may be more a more feasible option than cold products in terms of sensory quality.
Ultra-processed and processed foods may be an easy option, but the high salt, sugar, and fat levels associated with these products have been shown to promote overeating and may contribute to obesity-related illnesses.
In many high-income countries, around 75% of salt in the diet comes from processed foods and food consumed outside the home. What’s more, the growing demand for convenience, the affordability of processed options compared to fresh alternatives, and food preservation advancements allowing for longer shelf life, are driving the rising consumption of processed foods.
Sodium reduction is understandably a key focus for many in the food industry, and in turn, salt alternatives are being explored. Yet, reducing salt in some formulations can lead to undesirable changes to the taste, mouthfeel, and shelf life of a product. This makes it challenging for food manufacturers to maintain product quality and ensure it stays appealing to consumers.
Research has shown that a 2-5% reduced sodium content in a product does not impact consumers' acceptance of a food product, but when this content reduction reaches around 30%, there is a loss in flavour perception and alternatives need to be used to compensate.
A team of researchers from the School of Nutrition and Dietetics at Acadia University in Canada investigated the potential of grape pomace as a natural ingredient to reduce sodium tomato soup and vegetable juice.
The pomace, a byproduct of winemaking, is rich in fibre and polyphenols and offers functional and nutritional benefits. Using the product in reformulation – as a salt substitute –, has the potential to create lower-sodium and potentially more healthy product offerings, with the bonus of simultaneously reusing the environmental waste produced by the wine industry.
However, its impact on sensory attributes means consumer acceptance is not a given. The study, published in The Journal of Food Science explored this concept, assessing both consumer acceptability of products formulated with grape pomace and changes in sensory properties like flavour and saltiness perception.
The researchers suggest that the by-product, which consists of grape skins, seeds, and stems, could serve as a viable salt alternative due to its high concentration of dietary fibre, which has been shown to enhance texture and mouthfeel, and its polyphenol content, which can impart complex flavour profiles, and enhance the overall taste profile of food and sensory experience, potentially masking the need for added salt. In addition, the wine-like flavour and aroma compounds of the pomace can enhance low-sodium foods, similar to those imparted by herbs and spices.
To determine how successful the pomace was as a salt substitute, the team conducted two trials: one with tomato soup, involving 88 participants, and the second with vegetable juice, involving 99 participants.
The researchers selected the soup and juice for their high salt content and savoury flavour profile, as they believed these aspects would potentially complement the flavours of pomace.
The team then selected commercial low-salt tomato soup and regular vegetable juice. To create the control batches of soup and juice, they added salt to the sample (0.75% of the weight of the total juice or soup). To create the test batches, they added salt (0.15% of the weight of the total juice or soup) and grape pomace (1.67% of the weight of the total juice or soup) to the sample.
The control samples, with no pomace, served as a baseline for the test sample, with added pomace. The test samples simulated a 30% sodium reduction in both products.
Participants were asked by the researchers to rate various aspects of the products, including flavour, appearance, texture/mouthfeel, saltiness intensity, and overall liking. The ratings of the control (no pomace added) and test samples (added pomace) were then compared against each other.
The team found that the addition of the pomace in the tomato soup did not have a significant impact on the appearance or texture of the product. Vegetable juice with pomace did however receive lower scores compared to the control sample, for both appearance and texture.
Flavour ratings for test samples of both the juice and soup were rated significantly lower than the control samples, indicating that grape pomace had a negative impact on flavour perception.
No significant differences were observed in saltiness between the test and control samples of the tomato soup, suggesting that the pomace could potentially replace salt in this product. The test sample of vegetable juice did have a higher perceived saltiness level than the control, but the difference was minor.
When it came to flavour profile assessments, participants described the control soup more positively – savoury, sweet, tomato flavour – than the test soup – bitter, sour, wine-flavour. Similar results occurred for the juice samples, where the test sample was associated with higher bitterness and sourness.
Overall liking scores indicated that the control and test tomato juice samples were not significantly different. The vegetable juice test sample was rated significantly lower than the control juice.
The addition of grape pomace in tomato soup did not significantly affect consumer perception of appearance, or texture of the product. This suggests that pomace, when incorporated into a heated product like a soup, may be better solubilised.
A 2023 study found that heating grape seed flour converts insoluble phenolic compounds into soluble forms, which the researchers in the current study argue may have led to better solubility in the tomato soup compared to the vegetable juice.
Of note, the addition of grape pomace did not impact the perceived saltiness of the tomato soup, suggesting the potential of pomace as a partial sodium replacement in soups and stews.
One limitation noted by the team was that participants were not informed of the health benefits of the pomace before rating the soup and juice, which could have influenced their perceptions of the samples. The researchers argued that previous studies have demonstrated that when consumers are informed about the nutritional benefits of a product, it can improve hedonic ratings—indicating product labelling and claims focusing on the health and sustainability aspects of grape pomace could play a role in consumer appeal.
The researchers concluded that while grape pomace can be successfully incorporated into tomato soup without significantly impacting consumer acceptance, when the pomace is added to vegetable juice the results are less than desirable, and result in texture issues and off-flavours which negatively impact consumer liking.
While the study demonstrated the potential of grape pomace as a functional ingredient for sodium reduction in certain formulations, more work and research is needed to address its sensory challenges.
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