Evaluation of multicomplex systems on pomegranate concentrate loaded alginate hydrogels by low-field NMR relaxometry: physicochemical characterization and controlled release study

Alginate (ALG) and various gums are potential biomaterials to be employed in hydrogel designs for both food and biomedical applications. This study evaluated a multicomplex design by combining food grade polymers to examine their polymer-polymer interactions and design an oral delivery system for pomegranate concentrate (PC). ALG was replaced with gum tragacanth (GT), xanthan (XN) and their equal combinations (GT:XN) at 50% ratio in hydrogel fabrication. In addition to CaCI2 in binding solution, honey (H) and chitosan (CH) were also used during physical crosslinking. Relaxation time constants in NMR indicated poor ability of GT for water entrapment especially in the presence of honey (S2H). They also confirmed FTIR results indicating similar trends. Strong negative correlations were observed between T2 and texture results. GT replacement of ALG especially in the use of single CaCI2 (S2) promoted higher PC release up to 80% in digestive media compared to XN substitution (S3). This study promoted use of LF NMR as an indicator for polymer mixture characterization in complex gels. ALG based gels could be modified by replacing ALG with different kinds of gums and with use of different binding solutions to regulate target compound release in food and pharmaceutical fields.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05730-2.

The moisture adsorption, caking, and flowability of silkworm pupae peptide powders: The impacts of anticaking agents

This study aimed to explore the impacts of different anticaking agents on the moisture adsorption, caking, and flowability of silkworm pupae peptide powders (SPPP). The characteristics of water distributions in SPPP with anticaking agents were investigated by LF NMR. The morphological observation of powders was analyzed by scanning electron microscope. Moisture sorption curves and moisture sorption isotherm curves indicated that calcium stearate, silicon dioxide and calcium silicate of 20 % reduced hygroscopicity and increased critical relative humidity. The angle of repose analysis revealed that anticaking agents could also increase flowability (45°-49°). LF NMR analysis indicated that anticaking agents reduced the moisture adsorption ability of SPPP. Scanning electron microscope observations demonstrated different shapes and surface morphology of SPPP using different anticaking agents. Notably, silicon dioxide served as the most effective anticaking agent by forming a physical barrier. Overall, anticaking agents can effectively delay moisture adsorption and deliquescence of SPPP by different anticaking fashions.

Effect of Flaxseed Oil Cake Extract on the Microbial Quality, Texture and Shelf Life of Gluten-Free Bread

Extending the shelf life of gluten-free bread (GFB) is a challenge. Mainly due to the ingredients used and their characteristics, GFB has numerous drawbacks such as unsatisfactory texture and rapid staling beyond a low nutritional value. In the present study, flaxseed oil cake extract (FOCE) was used to replace water (25-100%) in GFB formulations in order to test FOCE's potential to reduce GFB staling and extend microbial stability. Texture (TPA test), water activity (LF NMR), acidity (pH measurements) and microbiological quality of GFBs were tested. Moreover, the content of a lignan with broad health-promoting potential, secoisolariciresinol diglucoside (SDG), in GFB with FOCE was analyzed. The results showed that the use of FOCE enriched experimental GFB in valuable SDG (217-525 µg/100 g DM) while not causing adverse microbiological changes. A moderate level (25-50%) of FOCE did not change the main texture parameters of GFB stored for 72 h, the quality of which was comparable to control bread without FOCE. Meanwhile, higher proportions of FOCE (75-100% of water replacement) shortened GFB shelf life as determined by water activity and texture profile, suggesting that GFB with FOCE should be consumed fresh. To summarize, FOCE at moderate levels can add value to GFBs without causing a drop in quality, while still fitting in with the idea of zero waste and the circular economy.

Effects of CaCl2 on salting kinetics, water migration, aggregation behavior and protein structure in rapidly salted separated egg yolks

Salted egg yolks are valued by consumers for their delicious taste good processing characteristics. To improve the quality of rapidly salted separated egg yolks, we compared changes in the salting kinetics, textural properties, water migration, protein aggregation and structure of salted egg yolks in the presence or absence of CaCl₂ for 24 h. CaCl₂ increased the mass transfer driving force and diffusion coefficient during the salting process; as a result, the salted egg yolks exhibited increased hardness and decreased springiness and cohesiveness. Through low field nuclear magnetic resonance (LF NMR), it was confirmed that CaCl₂ promoted the precipitation of lipids and the dehydration of egg yolk. Furthermore, CaCl₂ promoted the bulk aggregation of proteins. The analyses of protein structures showed that the contents of β-sheets and irregular curls in CaCl₂-salted egg yolk protein increased, while the contents of α-helices and β-turns decreased. CaCl₂ affected the microenvironment of tryptophan residues and embedded these residues, enhancing protein aggregation. Based on the comprehensive information obtained in this study, adding CaCl₂ to the salting solution improved the degree of protein polymerization in egg yolk; thus, this method might be used to improve the quality of egg yolks separated by salt.

Water Behavior of Emulsions Stabilized by Modified Potato Starch

Starch is a widely known and used emulsion stabilizer. In order to improve its properties, various types of modifications are made that change its ability to emulsify and stabilize. This paper describes the analysis of the molecular dynamics of water using low-field nuclear magnetic resonance (LF NMR) in oil-in-water emulsions obtained with the use of physically or chemically modified potato starch. The analysis of changes in spin-spin and spin-lattice relaxation times depending on the temperature allowed the activation energy value of water molecules in the analyzed emulsions to be determined. It has been shown that the presence of starch influences the values of spin-lattice T₁ and spin-spin T₂ relaxation times, both in the water and the oil phase, and the observed changes largely depended on the type of starch modification. Both types of analyzed starches also differently influenced the energy of activation of rotational movements of water molecules. On the basis of the analyses carried out with the use of LF NMR, it can be concluded that physically modified starch acts not only as a stabilizer, but also as an emulsifier, while acetylated starch does not exhibit good emulsifying properties.

Study on the mobility of water and its correlation with the spoilage process of salmon (Salmo solar) stored at 0 and 4 °C by low-field nuclear magnetic resonance (LF NMR 1H)

Low-field nuclear magnetic resonance (LF NMR) was used to investigate the water mobility of salmon during cold storage and the correlation between texture, freshness, sensory quality and transversal relaxation times (T₂) of salmon were studied. With the increasing of cold storage time, trapped water (T₂₂), sensory, water holding capacity and cooking loss were descended while free water (T₂₃), TVB-N and TBA were increased steadily, that reflected the quality of salmon quality visually. There was a significant correlation between sensory, hardness, TBA, cooking loss, K value and LF NMR parameters. The study showed that LF NMR was sensitive to different storage conditions which may be applied to monitor the quality of fish muscle, when the spoilage mechanism was affected by water properties and muscle structure.