Quality Attributes of Cold-Stored Khalal Barhi Dates Treated with Guava Leaf Extract and/or Lactic Acid as Natural Preservatives.

The use of natural ingredients to preserve the quality of fresh fruits is a promising approach to healthier products and a more sustainable industry. The present study was carried out to assess the effect of lactic acid (LA) and guava leaf extract (GLE) as natural preservatives on the quality parameters of Khalal Barhi dates. Physicochemical properties, antioxidant activity, color parameters, firmness, sensory properties, and yeast and mold counts of date fruits were evaluated during five weeks of storage at 4 ± 1 °C. The bioactive compounds in GLE were estimated by HPLC, which exhibited that GLE contains significant amounts of bioactive compounds, mainly, phenolics and flavonoids. With prolonged storage, the moisture content decreased, while the total soluble solids (TSS) increased in all samples. Similarly, a slight decrease in the pH with a concomitant increase in titratable acidity (TA) was observed throughout the storage. Generally, the samples treated with natural preservatives revealed lower changes in moisture content, TSS, pH, and TA than the control. The results exhibited decreased total phenolic content (TPC) and antioxidant activity for all samples with extended storage. The GLE and LA + GLE treatments significantly (p < 0.05) increased TPC and antioxidant activity on day 0 and preserved higher values of both during storage. Additionally, a decrease in the L* and b* values with an increase in the a* values of all samples was observed with advancement of storage. The LA + GLE treatment minimized the changes in color parameters and maintained higher firmness values during storage. Similarly, the sensory properties of all samples decreased with prolonged storage, but insignificant (p > 0.05) differences were found among the samples. Dipping treatments inhibited microbial growth over time, with the lowest yeast and mold counts achieved by the LA + GLE treatment. It can be concluded that the LA + GLE treatment has a protective effect on Khalal Barhi dates by minimizing post-harvest changes and decreasing the microbial load.

Valorization of Second-Grade Date Fruit Byproducts and Nonstandard Sweet Potato Tubers to Produce Novel Biofortified Functional Jam.

Byproducts of second-grade dates and sweet potato tubers of noncommercial standard are produced along with the main product and are just as important as the main product but cannot be sold in the open market, as they may not be considered acceptable by consumers. Such byproducts can be valorized through the manufacture of a wide range of functional food products with high market appeal, such as jams. The research approach of this study included measuring antioxidant activity, total flavonoids, polyphenols, physicochemical and color indices, pH, and total sugar, as well as conducting a sensory evaluation, of mixed jams composed of different ratios of date jam (DFJ) to sweet potato jam (SPJ), namely, DP1 (80:20), DP2 (70:30), DP3 (60:40), and DP4 (50:50). To date, no other studies have considered producing mixed jam from dates and sweet potato byproducts. The sensory evaluation results indicated that jam DP4 (consisting of 50% date and 50% sweet potato) had the maximum overall acceptability. This investigation reveals the potential of using mixed byproducts in jams as natural functional ingredients, suggesting the economic value of valorization byproducts as low-cost ingredients to expand the properties, nutritional value, antioxidant content, and overall acceptability of jams. The discovered optimal mixed fruit jam has significant potential for further development as a commercial product.

Effects of Pomegranate Peel Extract and/or Lactic Acid as Natural Preservatives on Physicochemical, Microbiological Properties, Antioxidant Activity, and Storage Stability of Khalal Barhi Date Fruits.

The use of natural preservatives in the storage of fresh fruits is a promising approach to healthier and more sustainable food processing. The current study was conducted to evaluate the effect of pomegranate peel extract (PPE) and lactic acid (LA) as natural preservatives on the shelf life of Khalal Barhi date fruits. Physicochemical properties, antioxidant activity, color parameters, texture profile, sensory characteristics, and microbiological quality of date fruits were evaluated during six weeks of cold storage (4 ± 1 °C). The bioactive compounds in PPE were determined by HPLC analysis, which showed that PPE is a rich source of bioactive compounds, particularly phenolics and flavonoids. The results exhibited decreased moisture content (from 68.36-68.43 to 62.13-63.11%) and an increased soluble solids content (from 27.16-27.24 to 31.45-33.91%) in all samples with prolonged storage. Likewise, a slight decrease in the pH (from 6.00-6.28 to 4.89-5.29) with an increase in acidity (from 0.12-0.14 to 0.23-0.27%) during storage was observed. Generally, treated samples showed lower changes in moisture content, soluble solids content, pH, and acidity than the control. A decrease in total phenolic content (TPC) (from 8.22-12.36 to 3.19-5.17 mg GAE/g) and antioxidant activity (from 44.11-68.26 to 23.84-38.52%) of all samples was observed with progressed storage, meanwhile, the treatment with PPE significantly (p < 0.05) increased TPC with a concomitant increase in antioxidant activity and maintained higher values of both throughout storage. The results exhibited a decrease in L* (from 54.87-55.92 to 41.68-45.68) and b* (from 36.25-37.09 to 23.59-25.42) values of all samples, while the a* value of all samples increased (from 1.29-1.40 to 2.22-2.43) with storage. Dipping treatment in PPE solution improved the color, exhibited the lowest change in color parameters, and maintained better texture properties during storage. Similarly, sensory properties decreased (from 8.21-8.66 to 6.71-7.21) during storage with insignificant (p > 0.05) differences among samples. Dipping treatments inhibited the growth of yeasts and molds over time, with the lowest microbial count recorded in the PPE-treated samples. It can be concluded that PPE was found to have protective effects on Khalal Barhi date fruit quality by controlling post-harvest changes and lowering the microbial load.

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.

Physicochemical and Sensory Properties and Shelf Life of Block-Type Processed Cheeses Fortified with Date Seeds (Phoenix dactylifera L.) as a Functional Food.

Processed cheese has rapidly been established as a commercial product in recent years. A new ingredient, a byproduct from date fruit seed (DFS), was obtained and tested as a fortified fiber from food industrial waste in block-type processed cheese. This is the first inclusive investigation to report such a test. Different concentrations of DFS (0%, 5%, 10%, 15%, and 20%) were added to block-type processed cheese as a partial substitution for butter. The current investigation was undertaken to estimate the impact of the partial substitution of butter by DFS and its effect on the product's quality in terms of its shelf life and physicochemical, microstructure, color, and sensory properties. Quality was assessed over a 150-day storage period. The results indicate that adding DFS to cheese increased its nutritional value due to the addition of fiber. Additionally, the texture profile of cheese was decreased in terms of hardness, adhesion, springiness, and cohesiveness. The overall structure of cheeses became less compact and had a more open cheese network, which increased with increasing DFS% and duration of storage. Moreover, DFS exhibited the darkest color with increasing ratios of supplementary DFS and duration of storage. Based on the results found in the present investigation, it was concluded that an acceptable quality of block-type processed cheese could be achieved using DFS fiber at 5% and 10% levels of fortification.

Carboxymethyl-Cellulose-Containing Ag Nanoparticles as an Electrochemical Working Electrode for Fast Hydroxymethyl-Furfural Sensing in Date Molasses.

Novel biosensors based on carboxymethyl cellulose extract from date palm fronds containing Ag nanoparticles as an electrochemical working electrode for fast hydroxymethylfurfural (HMF) sensing in date molasses were prepared. The morphological, structural, and crystallinity characteristics of the prepared Ag@CMC were described via SEM, DLS, TEM, and XRD. In addition, Raman spectroscopy and UV-VIS spectroscopy were performed, and thermal stability was studied. The investigated techniques indicated the successful incorporation of AgNPs into the CMC polymer. The sensing behavior of the prepared AgNPs@CMC electrode was studied in terms of cyclic voltammetry and linear scan voltammetry at different HMF concentrations. The results indicated high performance of the designed AgNPs@CMC, which was confirmed by the linear behavior of the relationship between the cathodic current and HMF content. Besides, real commercial samples were investigated using the novel AgNPs@CMC electrode.