Effect of Tamarillo Fortification and Fermentation Process on Physicochemical Properties and Nutrient and Volatiles Content of Yoghurt

Experimental Investigation and Modeling for the Influence of Adding Date Press Cake on Drinkable Yogurt Quality

The extraction of date syrup produces a large quantity of by-product known as date press cake (DPC). This study aimed to utilize valuable ingredients of the DPC by adding 0 (Control), 2, 4, and 6% (g/100 g) of its powder to drinkable yogurt before fermentation. The physicochemical properties, texture profile, and sensory evaluation of the treated DPC-based drinkable yogurt (DPC drinkable yogurt) were measured after fermentation and 5, 10, and 15 days of storage at 4 °C. The modeling of the most critical quality attributes, i.e., pH, acidity, syneresis, water holding capacity (WHC), viscosity, and color difference (ΔE), was conducted to predict their values based on the DPC percentage and storage period. The DPC drinkable yogurt’s total solids, protein, and fat ranged between 11.19–11.83, 3.10–3.42, and 2.26–2.34%, respectively. Adding 2–6% DPC slightly increased the pH of DPC drinkable yogurt and decreased its acidity (p > 0.05) during storage. Increasing the DPC percent in DPC drinkable yogurt decreased the syneresis value, and WHC increased during storage. The color parameters and viscosity of DPC drinkable yogurt recorded the highest value at the end of the storage period for all treatments and increased steadily with the increase in DPC. The evaluation of the prediction models indicated that the predicted values were close to the actual experimental values for pH (R2 = 0.779), acidity (R2 = 0.973), syneresis (R2 = 0.961), WHC (R2 = 0.989), viscosity (R2 = 0.99), L* (R2 = 0.919), a* (R2 = 0.995), b* (R2 = 0.922), and ΔE (R2 = 0.921). The textural analysis indicated that increasing the concentration of DPC in the DPC drinkable yogurt increased hardness (g), springiness, cohesiveness, and gumminess and decreased adhesiveness and resilience during cold storage. The evaluation of sensory acceptance during the cold storage of the DPC drinkable yogurt was conducted by 30 expert panelists. Each panelist received four cups of 10 mL drinkable yogurt treatments at 5–10 °C. The evaluation results indicated that adding 2% of DPC was closest in overall sensory acceptability to the control sample (p < 0.05). This study revealed the potential use of DPC in drinkable yogurt as a natural, functional, and low-cost ingredient to improve the fiber content, physicochemical properties, and overall acceptability. Therefore, the fermented DPC-based yogurt drink has the potency to be a practical, value-added, and novel alternative to dairy-based yogurt.

Sensorially accepted Mangifera indica and Myrciaria dubia yogurts with high ascorbic acid content

Ascorbic acid deficiency has been associated with several health conditions. The objective of this study was to evaluate the content of ascorbic acid and the sensorial qualities of Mangifera indica and Myrciaria dubia yogurts. Four yogurt treatments were elaborated with different concentrations of these fruits (T1: 15% and 5%; T2: 15% and 10%; T3: 20% and 5% and T4: 20% and 10%) respectively, compared with a control treatment (CT: yogurt with 15% of Fragaria vesca). The ascorbic acid contents of the different treatments were determined by spectrophotometry, with values in the following order (T1: 63.2 mg/100 g; T2:114.3 mg/100 g; T3: 57.3 mg/100 g; T4: 115.1 and the control treatment CT:11.5 mg/100 g). The sensorial evaluation consisted of the application of a hedonic scale of 5 points (1: I dislike it very much; 2: I dislike it; 3: I neither like it nor dislike it; 4: I like it; 5: I like it a lot), results show evidence that the acidity level had a significant influence during the sensory evaluation. Treatment (T3) showed the greatest preference. The use of Mangifera indica and Myrciaria dubia in the treatments studied ensured ascorbic acid concentrations compared to the control treatment. This was significantly appreciated by consumers when the percentage of Myrciaria dubia was less than 10% of the total mass of the yogurt.

Effect of In Vitro Gastrointestinal Digestion on Amino Acids, Polyphenols and Antioxidant Capacity of Tamarillo Yoghurts

Laird’s Large tamarillo powder is high in protein (10%) essential amino acids (EAAs), gamma-aminobutyric acid (GABA) and polyphenols (0.6% phenolics plus anthocyanins) and fibre 25%. This study aimed to investigate, using a standardized static in vitro digestion model, the stability of amino acids and antioxidant capacity of polyphenols in yoghurt fortified with 5, 10 and 15% tamarillo powder either before (PRE) or after (POS) fermentation. Compared to plain yoghurt, the fruit polyphenols (rutinosides and glycosides) were retained and substantial increases in FEAAs (free essential amino acids), total phenolic content (TPC) and antioxidant activity were observed particularly at the end of intestinal phase of digestion. Together with SDS-PAGE results, peptides and proteins in tamarillo yoghurts were more easily digested and therefore may be better absorbed in the small intestine compared to the control. TPC and antioxidant activity of fortified yoghurts increased significantly after in vitro digestion. Relatively high bioaccessibilty of chlorogenic acid and kaempferol-3-rutinoside in digested PRE samples was observed. The results suggest that the yoghurt matrix might protect some compounds from degradation, increasing bioaccessibility and in the small intestine allow increased absorption and utilization possible. Fortification would deliver intact polyphenols and fibre to the large intestine and improve gut health. Further research of acceptability, shelf life, and then trials for health effects should be implemented.