Wine by-product increases dietary fibre content of yogurt – US research

Researchers at Oregon State University’s Department of Food Science and Technology claim that WGP could be used as an alternative source of anti-oxidant dietary fibre to fortify yogurt and salad dressing products.

WGP, which is the solid remains of grapes following winemaking process, contains phenolic compounds (anti-oxidant) and dietary fibre.

According to the research, there is increasing interest in the use of fruit processing waste as functional food ingredients, as they are often a rich source of dietary fibre.

In the resulting report, Wine grape pomace as antioxidant dietary fibre for enhancing nutritional value and improving storability of yogurt and salad dressing, ​the researchers also claim that that fortifying yogurt with WGP could delay lipid oxidation – a major factor in food quality deterioration.

Alternative source of dietary fibre​

Oregon State University researchers, and authors of the study, Angela Tseng and Yanyun Zhao evaluated three different forms of WGP - dried whole grape pomace (WP), pomace liquid extract (LE) and freeze dried liquid extract (FDE).

“This study demonstrates that Pinot Noir wine grape pomace may be utilised as an alternative source of antioxidant dietary fibre to fortify yogurt and salad dressing for not only increasing dietary fibre and total phenolic content but also delaying lipid oxidation of samples during refrigeration storage,”​ said the report.

“Although products fortified with the pomace extracts (liquid and freeze dried) obtained the most similar physicochemical properties to the control (no pomace added), those fortified with dried whole pomace powders (WP) has higher dietary fibre content.”​

Tseng and Zhao evaluated the dietary fibre content and storability of the WGP-fortified lab-made yogurt and store-bought salad dressing samples over a period of between 21 and 28 days.

Before evaluation began, the researchers added one, two, and three gram measures (referred to as 1%, 2% and 3% respectively) of WGP was added to 100g samples of yogurt and stirred. The samples were then packed and stored in a refrigerator at 4°C and evaluated after one day, seven days, 14 days, and 21 days.

The highest anti-oxidant dietary fibre content was obtained in the yogurt fortified with three grams of WGP.

“Consumer acceptance” of WGP-fortified yogurt​

Tseng and Zhao also evaluated the consumer acceptance of WGP-fortified yogurt and salad dressing through a consumer sensory study.

Twelve panellists aged between 18 and 39 were recruited to participate in the evaluation of the products fortified with WP.  Yoplait-brand vanilla flavour yogurt mixed with 5.59% grape juice concentrate was used as a control to avoid colour and flavour discrimination.

The recruits were asked to rate the appearance, flavour, and texture quality of the samples.

Yogurt samples fortified with one gram of WGP proved most popular with consumers during the sensory tests.

Source: Food Chemistry​

Wine grape pomace as antioxidant dietary fibre for enhancing nutritional value and improving storability of yogurt and salad dressing​​

Authors: Angela Tseng, Yanyun Zhao​