## 2 Materials and Methods
### Mango Peel Powder Production and Characterization  
MPP was prepared from mango peels that were first washed under running water (\(25\pm 1\)\({}^{\circ}\)C), then sanitised with 2% NaClO solution for 15 min and finally rinsed thoroughly to remove residual chlorine. To ensure uniformity during the dehydration process, the peels were sliced to a thickness of 0.5 \(\pm\) 0.1 mm and stored at -20 \({}^{\circ}\)C until further processing. Initially, the peels underwent treatment in an ultrasonic bath (DU-32, ARGOlab, Modena, Italy) at 30 \({}^{\circ}\)C for 15 min at 22 kHz and 70 W, significantly reducing the overall drying time [22]. Subsequently, the mango peels were dehydrated in a tray dryer, as described by [PERSON] et al. [23], at 60 \({}^{\circ}\)C for 3 h. During the drying process, the trays with peels were weighed every 30 min to halt the process once a 20% dry residue (DR) was reached, thereby preserving bioactive compounds. The %DR was calculated using the following Equation (1):  
\[\%\mathrm{DR}=(\mathrm{c}-\mathrm{a})/(\mathrm{b}-\mathrm{a})\times 100 \tag{1}\]  
where  
a is the weight of the empty tray;  
b is the weight of the tray with the product before drying;  
c is the weight of the tray with the product after drying. The colour of raw materials (MPP and semolina) was assessed using a digital colorimeter (Minolta, mod. CR-300; Osaka, Japan) to evaluate the degree of browning based on the CIELab colorimetric system. This system determines colour using three coordinates: L\({}^{\star}\) for brightness (with L\({}^{\star}\) = 0 representing black and L\({}^{\star}\) = 100 representing white), a* for the green/red colour index (where a* = -100 indicates green and a* = +100 indicates red), and b* for the blue/yellow colour index (with b* = -100 signifying blue and b* = +100 signifying yellow). Chroma values (C*), indicating the quantitative attribute of colour intensity, were calculated using Equation, as follows (2):  
\[\mathrm{C}^{\star}=\surd(\mathrm{a}^{2}+\mathrm{b}^{2}) \tag{2}\]  
Hue angle (h\({}^{\circ}\)), describing the colour tone, was calculated using the following Equation (3):  
\[\mathrm{h}^{\circ}=\arctan\left(\mathrm{b}^{\star}/\mathrm{a}^{\star}\right) \tag{3}\]  
The mango peel was processed using an ultra-centrifugal mill ([PERSON], Pulverisette 14, Lainate, Italy) at a speed of 10,000 rpm for 10 s. The resulting mango peel powder (MPP) was sieved using a [PERSON] centrifugal apparatus (Mill ZM1, Haan, Germany) equipped with a 250 \(\upmu\)m stainless steel ring sieve. The MPP was then analysed for colour, weighed, packed into sealed glass containers, and stored at room temperature (20 \(\pm\) 1 \({}^{\circ}\)C). MPP underwent microbiological analysis to identify unwanted microbial groups during food fermentation. Ten grams of MPP were homogenized using a BagMixer(r) 400 stomacher (Interscience, Saint Nom, France) and then serially diluted. All cell suspensions were inoculated in agar media to promote the growth of different microbial groups, as follows: total mesophilic microorganisms (TMM) as well as total psychrophilic microorganisms (TPM) were cultivated on plate count agar (PCA) and incubated aerobically at 30 \({}^{\circ}\)C for 72 h and at 7 \({}^{\circ}\)C for seven days, respectively; yeasts were cultivated on yeast peptone dextrose (YPD) under aerobic incubation at 28 \({}^{\circ}\)C for 48 h; members of the Enterobacteriaceaeiaceae family were incubated on violet red bile glucose agar (VRGBA) under microaerobic incubation at 37 \({}^{\circ}\)C for 24 h; total coliforms were incubated on violet red bile agar (VRBA) under microaerobic incubation at 37 \({}^{\circ}\)C for 24 h; pseudomonads were incubated on _Pseudomonas_ agar base (PAB) supplemented with cephaloridine sodium fusidate cetrimide under aerobic incubation at 25 \({}^{\circ}\)C for 48 h; _Escherichia coli_ and _Salmonella_ spp.