*2.4. Technological Characteristics of the Bread*

## 2.4.1. Bread Texture

Bread texture was evaluated using a texturometer TA-XTplus (Stable MicroSystems, Surrey, UK) in penetration mode. Each bread sample was cut into slices with a height of 20 mm and 120 × 100 mm rectangular shape, and slices rested for 15 min before testing. An acrylic cylindrical probe with 10 mm diameter pierced 5 mm of the sample at 1 mm/s of crosshead speed, with a load cell of 5 kg, according to the method earlier described in reference [12]. Comparison of the bread texture with different Yg and Cc contents was performed in terms of firmness.

Bread staling was evaluated measuring firmness during a storage time of 96 h, and the aging kinetics of the bread was described as a function of the dairy product incorporation according to a linear Equation (1)

$$\text{Firmness} = \text{A}^\* \text{ time} + \text{B},\tag{1}$$

where A can be considered the aging kinetics and B the initial firmness.

## 2.4.2. Quality Parameters of Bread

Bread moisture was determined according to the standard method AACC 44–15.02. Water activity (aW) variations were determined at room temperature (Hygrolab, Rotronic).

Bake loss (BL) of breads, which is defined as the amount of water and organic material (sugars fermented and CO2 released) lost during baking [15], was calculated, according to the Equation (2).

$$\text{Bake loss } (\%) = \left[ (\text{W}\_{lb} - \text{W}\_{ab}) / \text{W}\_{lb} \right] \times 100 \tag{2}$$

where

*Wab*: weight of the loaf after baking;

*Wbb*: weight of the loaf before baking.

Bread volume was determined by rapeseed displacement according to the standard method AACC 10-05.01 after 2h of cooling down [8]. Specific bread volume was calculated using Equation (3).

$$\text{Specific volume (cm}^3\text{/g)} = \text{bread volume (cm}^3\text{)} \text{bread weight (g)} \tag{3}$$

Knowing the weight and the volume of the bread, the specific weight (g/cm3) can also be estimated using the Equation (4), i.e., the reciprocal of specific bread volume.

$$\text{Specific weight (g/cm}^3) = \text{bread weight (g)} \text{bread volume (cm}^3) \tag{4}$$

All the experiments were done at least in triplicate.

#### *2.5. Image Analysis of the Bread Slices*

The gas cell number of the crumb breads was evaluated 120 min after production using image analysis technology. Images of three slices of breads (control, yoghurt, and curd cheese breads) were scanned full-scale using an Image Scanner (Xerox Corporation, Webster, NY, USA).

A threshold method was used for differentiating gas cells, and the segmentation was performed manually by binarization of grey-scale images into black-and-white images using the Otsu and default ImageJ algorithms, carried out in the ImageJ-based Fiji 1.46 software package [16].

#### *2.6. Nutritional Composition of the Bread*

Total nitrogen content was analysed by the MicroKjeldahl method (ISO 20483:2006). The quantification was performed by molecular absorption spectrophotometric equipment (Skalar-Sanplus System, Auto-Analyser, Giesen, Germany) [17,18].

Fat content was determined according to NP 4168. Ash content was determined by incineration at 550 ◦C in a muffle furnace (AACC Method 08-01.01).

Total mineral contents were determined by inductively coupled plasma atomic emission spectrometer (ICP-AES: Thermo System, ICAP-7000 series). All the experiments were done in triplicate.
