Rheological Characteristics and Microstructure of Milk Yogurt as Influenced by Quinoa Flour Addition

Optimal combination of cow and quinoa milk for manufacturing of functional fermented milk with high levels of antioxidant, essential amino acids and probiotics

The aim of this research was to produce Rayeb milk, a bio-fermented milk product that has important benefits for health and nutrition. The Rayeb milk was divided into five different treatments: T1 from cow milk, T2 from quinoa milk, T3 from a mixture of cow and quinoa milk (50%:50%), T4 from a mixture of cow and quinoa milk (75%:25%), and T5 from a mixture of cow and quinoa milk (25%:75%). As a starting culture, ABT-5 culture was used. The results demonstrated that blending quinoa milk with cow milk increased the total solids, fat, total protein, pH, acetaldehyde, and diacetyl values of the resulting Rayeb milk. Additionally, the total phenolic content, antioxidant activity, minerals, and amino acids-particularly important amino acids-in Rayeb milk with quinoa milk were higher. In Rayeb milk prepared from a cow and quinoa milk mixture, Lactobacillus acidophilus and Bifidobacterium bifidum were highly stimulated. All Rayeb milk samples, particularly those that contained quinoa milk, possessed more bifidobacteria than the recommended count of 106 cfu g-1 for use as a probiotic. Based on the sensory evaluation results, it is possible to manufacture a bio-Rayeb milk acceptable to the consumer and has a high nutritional and health values using a mixture of cow milk and quinoa milk (75%:25% or 50%:50%) and ABT-5 culture.

Effect of retrograded starch with different amylose content on the rheological properties of stored yogurt

Resistant starch (RS) promotes health benefits; however, when added to foods, it could change the rheological properties. The effect of adding different concentrations (2.5, 5, 7.5, and 10%) of retrograded corn starch with 27% (RNS) or 70% (RHS) amylose content on the properties of yogurt was evaluated through measurements of flow behavior and gel structure. Syneresis and resistant starch content were also assessed. Results were analyzed using multiple regression to describe the effect of starch concentration and storage time on the properties of yogurt added with RNS or RHS. Syneresis was reduced, RNS reinforced the structure increasing the water absorption capacity and the consistency index; meanwhile, RHS provided a yogurt containing up to 10 g of RS in 100 g of sample, allowing obtaining a functional dairy product. Creep-recovery test showed that adding RNS or RHS favored the matrix conformation, and the yogurt samples were able to recover. The final product behaved like a solid material with a firmer and more stable gel structure, resulting in a strengthened gel without weakening the yogurt structure, showing a characteristic like Greek-style or stirred yogurt depending on the type and concentration of retrograded starch.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05735-x.

Determination of antioxidant capacity, citric acid, phenolic compounds, physicochemical and sensory properties of Pepino marmalade yogurts enriched with erythritol and amaranth flour at different concentrations

This work aimed to evaluate the feasibility of fortifying Pepino marmalade containing erythritol and amaranth flour (1, 2, and 3%) as the source of antioxidants, dietary fiber, and polyphenols in yogurt for increasing nutritional value and improving storability. Both Pepino marmalade and amaranth flour increased the phenolic content, citric acid value, viscosity, and WHC of the yogurt samples. The diphenyl-1 picrylhydrazyl scavenging activity (DPPH), radical cation (ABTS^*+) scavenging assay, oxygen radical absorption capacity (ORAC), and ferric-reducing antioxidant capacity (FRAP) were found to be in the range of 4.5-46.6%, 166.2-1022 µg AAE/g, 2.61-4.49 µmol Trolox/g, and 4.9-23.88 µmol Fe²⁺/g respectively. As the concentration of marmalade and amaranth flour increased, the samples showed higher b* and lower a* and L* values. In addition, the panelists stated that they enjoyed the yogurt samples with Pepino marmalade and amaranth flour.

Quinoa flour as a skim milk powder replacer in concentrated yogurts: Effect on their physicochemical, technological, and sensory properties

Milk standardization with solids (i.e., nonfat milk solids, MSNF) for yogurt manufacture is traditionally achieved by the addition of skim milk powder (SMP). However, the addition of SMP to milk‐based yogurt increases lactose content and decreases both protein content and gel firmness. Thus, in this work, quinoa flour (QF; 0%, 25%, 50%, 75%, and 100% w/w) was used to replace SMP in concentrated yogurt. The physicochemical, textural, and sensory properties and microstructure of the yogurt were evaluated during cold storage. Generally, protein content, water‐holding capacity, and L* value decreased, while syneresis, textural attributes, and viscosity increased with increasing QF content. The substitution of high levels of QF (>25%, w/w) for SMP led to significantly shorter fermentation times, as compared to the control sample. The scanning electron microscopy observations showed significant changes in the yogurt microstructure as a consequence of QF replacement. Samples with 25% (w/w) substitution of QF and control had the highest scores in overall acceptance. According to the results, QF could be applied as an interesting raw material for concentrating the milk‐based yogurt at substitution level of 25% (w/w).

The Effects of Adding a Gel-Alike Curcuma longa L. Suspension as Color Agent on Some Quality and Sensory Properties of Yogurt

Color is an important characteristic of food products. This characteristic is related to consumer acceptability. To use the entire rhizome of Curcuma longa (CL) as a food colorant, a novel gel alike stable suspension (CLS) was previously developed using cellulose nanofibers (CNFs). Therefore, the present study was conducted to evaluate the CLS as a color additive on a stirred yogurt. Three concentrations of CLS were studied (0.1, 0.125, and 0.15 wt. %) and compared to yogurt without CLS. The obtained yogurts were characterized through the determination of pH, titratable acidity, syneresis, color and curcumin content after 1, 7, 14, and 21 days of storage. Additionally, rheological and sensory measurements were performed on the samples after one day of storage. Results show that the addition of CLS does not affect the pH and titratable acidity of the samples, but all the yogurts showed an increase in their syneresis during the storage time, showing a breakdown of the gel structure. Furthermore, the CLS suspension has the ability to impart a yellow color to yogurts, a characteristic that was stable during storage. Finally, the addition of 1 wt. % or 1.25 wt. % of CLS allows the development of a yogurt with adequate sensory perception.

Natural plant fibers obtained from agricultural residue used as an ingredient in food matrixes or packaging materials: A review

Every year, agrifood activities generate a large amount of plant byproducts, which have a low economical value. However, the valorization of these byproducts can contribute to increasing the intake of dietary fibers and reducing the environmental pollution. This review presents an overview of a wide variety of agricultural wastes applied in the formulation of different food products and sustainable packaging. In general, the incorporation of fibers into bakery, meat, and dairy products was successful, especially at a level of 10% or less. Fibers from a variety of crops improved the consistency, texture, and stability of sauce formulations without affecting sensory quality. In addition, fiber fortification (0.01-6.4%) presented considerable advantages in terms of rheology, texture, melting behavior, and fat replacement of ice cream, but in some cases had a negative impact on color and mouthfeel. In the case of beverages, promising effects on texture, viscosity, stability, and appetite control were obtained by the addition of soluble dietary fibers from grains and fruits with small particle size. Biocomposites used in packaging benefited from reinforcing effects of various plant fiber sources, but the extent of modification depended on the matrix type, fiber pretreatment, and concentration. The information synthesized in this contribution can be used as a tool to screen and select the most promising fiber source, fiber concentration, and pretreatment for specific food applications and sustainable packaging.

Effect of Three Types of Drying on the Viability of Lactic Acid Bacteria in Foam-Mat Dried Yogurt

In this research, foaming technology was applied to obtain powdered yogurt from commercial yogurt at lower temperatures than the typical temperatures used during the dehydration process; the viability of lactic acid bacteria (LAB) was evaluated after the application of different drying techniques (conventional drying, freeze drying, and vacuum drying). Three different formulas (F1, F2, and F3) based on a foaming agent (albumen), stabilizers (guar gum), and prebiotics sources (inulin and agave syrup) were developed. Foam stability was evaluated at different pH values through optimum time of foam (OTF), medium drainage time (MDT), and drainage volume (DV). Foam expansion (FE) and foam density (FD) were measured. The OTF ranged from 6 to 10 min. The MDT ranged from 4.3 to 27.3 min, depending on pH, while the DV varied from 14.1 to 16.2 mL only in F1. No drainage was evidenced in F2 and F3, showing the best stability. The F2 and F3 produced the best FE and FD values. The dried yogurt with different techniques showed a survival rate (SR) of up to 85% Log-CFU/mL, even with the conventional drying method. Sensorial trials were carried out in reconstituted product, with the freeze-dried yogurt showing higher scores. The foam formulas developed demonstrate the efficacy of both the dehydration of yogurt and the preservation of LAB.

The impact of quinoa flour on some properties of ayran

In this study, some physical, chemical, microbiological, and sensory properties of ayran produced from quinoa flour addition at different ratios (0.1, 0.2, 0.3, and 0.4%, w/v) were investigated. The effect of quinoa addition and storage time on pH, titration acidity, serum separation, L values and microorganism counts were statistically significant (p < .05). The counts of Streptococcus salivarus subsp. thermophilus and Lactobacillus delbruecki subps. bulgaricus had a wide range between 7.13 and 7.52 log CFU/mL and 3.62 and 3.98 log CFU/mlL At the end of the storage, the general appreciation score of the sample containing 0.2% quinoa flour was found to be higher than the other samples.

Impact of Inulin Addition on Properties of Natural Yogurt

The influence of the amount of inulin addition (3%, 6%, 9%, 12% or 15% w/w) on the physicochemical properties of natural yogurt was analyzed. The acidity (titration; pH), texture parameters (penetration test), viscosity curves (rotational rheometer), microrheology (macroscopic viscosity index, MVI; elasticity index, EI; solid-liquid balance—SLB; multi-speckle diffusing-wave spectroscopy, MS-DWS) and physical stability (syneresis; LUMiSizer test) of yogurts were investigated. All samples were non-Newtonian pseudoplastic liquids. The sample with 15% inulin content presented an approx. 4% higher pH value (4.34), 3-fold greater MVI and almost 5-fold higher penetration force, compared to the control sample (0% of inulin). In turn, the use of inulin addition in the range of 3–15% w/w resulted in a reduction of syneresis (p < 0.05). A linear decrease in the values of instability indexes and sedimentation velocities was noted in the function of inulin content increase (LUMiSizer test). The application of inulin (in the range of 3–15% w/w) as a functional additive to yogurts significantly contributed to enhancement of their physical stability. Summing up, the possibility of obtaining natural yogurts with a high content of this prebiotic has been demonstrated, thus such products can be classified as functional foods and a health claim can be put on the label.

Assessment of the Antioxidant Activity and Quality Attributes of Yogurt Enhanced with Wild Herbs Extracts

The milk and yogurt products assortment has expanded by their enhancement with herb extracts, fibres extracted from by-products of the fruit processing industry and also fresh spices. The aim of the present study was to test to what extent the addition of different herb extracts in yogurt will improve its qualitative characteristics and antioxidant activity. The aqueous extracts obtained from the four plants are considered in this study, respectively, thistle (Silybum marianum L.), hawthorn (Crataegus monogyna), sage (Salvia officinalis L.), and marjoram (Origanum vulgare L.). It was examined the effect of aqueous extracts prepared from four herbs (0.25/1%) (w/w) on yogurt’s qualitative characteristics (pH, titratable acidity, syneresis, water holding capacity, antioxidant activity, colour parameters, and rheological parameters) on both one day and 28 days after preparation. The final results show that the physicochemical and rheological properties of the yoghurt with herb extracts addition were improved compared to the control sample after 28 days of storage. The best results in terms of antioxidant properties were obtained when marjoram extract (Origanum vulgare L.) was incorporated. According to the data obtained, the best quality in terms of the physicochemical and rheological properties were in the case of the sample with 0.5% thistle extract (Silybum marianum L.) addition, while from point of view of the nutritional value, the best quality was in the case of the sample with 1% marjoram extract (Origanum vulgare L.) addition. The present study leads to the conclusion that yogurts enhanced with natural extracts may serve as functional food products, with significant health benefits.

Effect of pretreatment and membrane orientation on fluxes for concentration of whey with high foulants by using NH3/CO2 in forward osmosis

Usage of forward osmosis membrane in FO mode, in which active and support layers of the membrane were in contact with the feed and the draw solutions respectively, provided higher initial water flux (12L/m²h) than the usage of membrane in PRO mode (6L/m²h) having opposite orientation but fluxes approached to each other after 4h during concentration of whey with NH₃/CO₂ as draw salt. High organic and inorganic foulants of whey was considered as reason for observed result in addition to lower solute resistivity. Initial water flux (8,5L/m²h) was lower when pre-treatment was applied before forward osmosis process but final flux (4L/m²h) was equal flux of non pre-treatment. Reduction of solute resistivity or absence of hydraulic pressure can be reasons for lower initial flux. Detection of organic carbon but absence of lactose in draw solution showed passage of molecules being different than lactose into draw solution.