Development of Protein- and Fiber-Enriched, Sugar-Free Lentil Cookies: Impact of Whey Protein, Inulin, and Xylitol on Physical, Textural, and Sensory Characteristics

Abstract

Gluten-free (GF) diets often become nutritionally imbalanced, being low in proteins and fibers and high in sugars. Preparing GF foods with improved nutritional value is therefore a key challenge. This study investigates the impact of different combinations of whey protein (11.9%), inulin (6.0%) as dietary fiber, and xylitol (27.9%) as a sweetener used in the enrichment of green- and red-lentil-based gluten-free cookies. The cookies were characterized in terms of baking loss, geometric parameters, color, texture, and sensory profile. The results showed that these functional ingredients had different impacts on the lentil cookies made of different (green/red) lentils, especially regarding the effect of fiber and xylitol on the volume (green lentil cookies enriched with fiber: 16.5 cm3, sweetened with xylitol: 10.9 cm3 vs. 21.2 cm3 for control; red lentil cookies enriched with fiber: 21.9 cm3, sweetened with xylitol: 21.1 cm3 vs. 21.8 cm3 for control) and color (e.g., b* for green lentil cookies enriched with fiber: 13.13, sweetened with xylitol: 8.15 vs. 16.24 for control; b* for red lentil cookies enriched with fiber: 26.09, sweetened with xylitol: 32.29 vs. 28.17 for control). Regarding the textural attributes, the same tendencies were observed for both lentil products, i.e., softer cookies were obtained upon xylitol and whey protein addition, while hardness increased upon inulin enrichment. Stickiness was differently influenced by the functional ingredients in the case of green and red lentil cookies, but all the xylitol-containing cookies were less crumbly than the controls. The interactions of the functional ingredients were revealed in terms of all the properties investigated. Sensory analysis showed that the addition of whey protein resulted in less intensive “lentil” and “baked” aromas (mostly for red lentil cookies), and replacement of sugar by xylitol resulted in crumblier and less hard and crunchier products. The application of different functional ingredients in the enrichment of lentil-based gluten-free cookies revealed several interactions. These findings could serve as a starting point for future research and development of functional GF products.

Properties, Structure, and Acceptability of Innovative Legume-Based Biscuits with Alternative Sweeteners

“…However, the addition of oligofructose, though leading to an increase in biscuits made with wholemeal dicoccum wheat flour, led to a reduction in the spread ratio, probably due to the simultaneous presence of oligofructose and legume flour. Such an effect has been observed by Hajas et al [24] in wheat-lentil-wheat protein cookies. It should be noted that oligofructose progressively dissolves during baking, resulting in an increase in spread ratio and acting as a fat enhancer [44,45].…”

“…Legumes contain proteins that can interact with wheat proteins in the biscuit dough. The proteins in legumes, such as globulins and albumins, can contribute to the formation of a protein network [ 11 , 18 , 20 , 24 , 46 , 56 ]. This network affects the dough's viscoelastic properties, leading to changes in the microstructure of the baked biscuits.…”

“…An analogous behavior has been reported by Koukoumaki et al [ 18 ] for crackers prepared by replacing wheat flour with chickpea flour. Lentil-containing biscuits show physical attributes depending on a combination of interactive factors, among which are the high phenolic content, melanoidins formed through browning reactions, the high protein and fiber content, and the reducing sugars, sugar, and oligofructose presence [ 11 , 24 , 48 , 60 ]. The total color difference (Δ E ) for all biscuit formulations was significantly affected by independent variables in a pattern that followed the L ∗ value changes ( Table 3 ).…”

“…AwadElkareem and Shammari [ 72 ] also reported good acceptability for biscuits prepared with 5 and 10% lentil, with samples at the 5% level receiving the highest scores. Hajas et al [ 24 ] found that the overall liking of cookies prepared using red and brown lentils was higher compared to black lentil cookies, while no differences were detected between green, red, and yellow lentil cookies. Good overall acceptability has also been reported for biscuits containing 10% and 20% chickpea [ 73 ].…”

“…They suggested substitution at levels of 21 and 28%, which were considered the most excellent for all sensory attributes, showing that lentil flour at various proportions might provide biscuits with acceptable sensory quality. More recently, Hajas et al [ 24 ] investigated the preparation of gluten-free (GF) cookies based on green and red lentils using different combinations of whey protein, inulin as dietary fiber, and xylitol as a sweetener. Lentil products showed the same characteristics for textural attributes, noting that inulin addition increased the hardness of cookies.…”