Recently, there has been an increasing demand for milk alternative beverages derived from plant-based sources such as soy, oat, hemp, coconut, rice, and nuts, as animal milk substitutes. Reyes-Jurado et al. (2021) reported that the number of consumers who demand alternatives to bovine milk has significantly risen up to 61% since 2012. The expanding popularity of plant-based milk is attributed to several factors, including sustainability, healthy lifestyle, ethical concerns, lactose intolerance, dairy allergy, and animal welfare (Vogelsang-O’Dwyer, Zannini, & Arendt, 2021; Aydar, Tutuncu, & Ozcelik, 2020). Considering the effect of climate change and food security for the growing world population, more emphasis is being placed on plant-based diets (Poore & Nemecek, 2018; Willett et al., 2019). Generally, a plant-based milk is the extract of water-soluble compounds from plant materials with a milk-like appearance (Durand, Franks, & Hosken, 2003; Mäkinen, Uniacke-Lowe, O'Mahony, & Arendt, 2015). The most applied process for plant-based milk making includes separation of solid, product formulation, homogenization, heat treatment and packaging (Mäkinen, Wanhalinna, Zannini, & Arendt, 2016). Among plant-based milks, soy milk has been the most studied. Currently, soy milk-related products such as soy yoghurt, soy cheese and soy ice creams have been developed as an alternative to dairy-based products due to their nutritional benefits (Ningtyas, Tam, Bhandari, & Prakash, 2021). Soy protein provides a well-balanced amino acid composition and is a good source of nine essential amino acids (Nishinari, Fang, Guo, & Phillips, 2014). In addition to soy milk, other plant-based milks such as peanut, oat, almond, coconut, rice, and quinoa milks were successfully developed, while the global plant-based milk market keeps expanding (Jeske, Zannini, & Arendt, 2017). However, apart from soy protein, most plant proteins are often considered as incomplete due to a lack of some essential amino acids (Jäger et al., 2020). Vanga and Raghavan (2018) stated that there are various issues associated with current plant-based milk products, including low total number of calories, limited nutrient diversity, beany flavour and allergic reactions. These have motivated researchers to explore new plant sources as non-animal milk substitutes.
Lotus, Nelumbo nucifera Gaertn., is a perennial aquatic herb widely cultivated and consumed in Asia, Oceania and America (Liu et al., 2015). Most parts of the lotus exhibit excellent food and medicinal values (Zhang et al., 2015). Lotus seeds, the most prominent part, contain abundant functional ingredients, such as polyphenols, flavonols, procyanidins, alkaloids and polysaccharides (Liu et al., 2015; Yu et al., 2022). As the second largest component in lotus seed, lotus seed protein accounts for 19.85wt% on a dry weight basis (Zeng, Cai, Cai, Wang, & Li, 2013). Importantly, lotus seed protein reveals a high-quality amino acid composition, an FAO/WHO pattern of similar nutritional value to soy protein (Bangar, Dunno, Kumar, Mostafa, & Maqsood, 2022; Zeng et al., 2013). Zheng, Li, Zhang, Zheng, and Tian (2020) and Su et al. (2022) emphasized that lotus seed protein expresses excellent biological value with a high level of methionine and lysine and a lack of common allergens. Therefore, more attention has recently been paid to lotus seed proteins as a functional food ingredient (Zeng et al., 2013). Unlike soy protein, little information is available on the physicochemical and functional properties of lotus seed protein, which limits its application in the food industry (Jia et al., 2019).
Milk protein gelation is a significant step in cheese and yoghurt manufactures, which have great economic importance (Lucey, 2002). Over the last decade, there has been a growing interest in plant-based dairy products, including plant-based yoghurts and cheeses (Devnani, Ong, Kentish, & Gras, 2020). Recently, soy is the most popular plant-based source for yoghurt production because of its quantity, quality, and functional characteristics (Deng, 2021). Yang, Ren, Liu, Huo, and Li (2021) reported on the gelation mechanism of soy milk, which includes heat-induced protein denaturation and acid-induced protein coagulation. Heat-induced particle aggregates are an essential procedure for the formation of protein networks. Reducing the pH of heated soy milk to the isoelectric point results in protein aggregation (Ningtyas et al., 2021). Glucono-δ-lactone (GDL) is often used to mimic bacterial fermentation in model yoghurt systems and acid-induced gel (Vasbinder, van Mil, Bot, & de Kruif, 2001). It is an ester that slowly produces gluconic acid in water to decrease the pH, and is widely used to study the gelation of milk and soy proteins (Grygorczyk & Corredig, 2013; Kuipers, Alting, & Gruppen, 2007; Lucey, 2002). Grasso, Alonso-Miravalles, and O'Mahony (2020) pointed out that the main quality issues of plant-based yoghurts are appearance and texture properties, which are generally associated with phase separation. When plant-based milk is acidified, destabilization of the proteins leads to the formation of a non-continuous, weak gel, resulting in serum separation. Compared to dairy yoghurt, soy yoghurt exhibits a hard texture and lacks smooth sensations, making it hard to meet the requirements of consumers on smoothness, creaminess, soft texture and a less beany taste (Ningtyas et al., 2021). Mäkinen et al. (2015) investigated the physicochemical and acid gelation properties of UHT-treated commercial soy, oat, quinoa, rice and lactose-free bovine milk. Both soy and quinoa milk formed gels under the action of GDL with lower storage moduli compared with bovine milk gel. Further, the study showed that oat and rice milk did not gelify.
The physicochemical properties and acid gelation capability of protein, which play important roles in food systems, are not known for lotus seed milk. The current work was conducted to examine the primary structure, particle size distribution and viscosity of lotus seed milk. The effects of lotus seed milk concentration (5–20wt%) were also considered. In addition, the pH change during lotus seed milk gelation was monitored under the action of GDL. The properties of acid-induced lotus seed milk gels, including rheological properties, microstructure and syneresis, were determined. All the results on lotus seed milks and their acid-set gels were compared to 10wt% reconstituted skim milk and its acid-set gel as a control. To the best of our knowledge, this study is the first to report on the physicochemical and acid gelation properties of lotus seed milk.
Dried lotus seeds without seed coats and embryos were sold by Xiang Tan Lin Hong trading company Ltd. (Hunan, China) in 500g vacuumed packages without any additives. According to the label nutritional composition, every 100g of dried lotus seed contains 18.4g proteins, 1.2g fats and 65.5g carbohydrates. Low-heat skim milk powder (SMP) from Fonterra Ltd. (Hamilton, New Zealand). α-amylose (origin: Bacillus subtilis, 50 U/mg) was purchased from Shanghai Yuanye Bio-Technology Co., Ltd.
Chemical composition and SDS-PAGE analysis
The chemical compositions of LSM powder and SMP are reported in Table 1. The moisture content of LSM powder (∼6.0%) is higher than that of SMP (∼3.6%) due to the different drying methods used; freeze-drying for LSM and spray drying for skim milk, and also to their difference in molecular contents and structures. The carbohydrate content, hydrolysed starch for LSM (∼52.9%) and lactose for SMP (∼51.7%) is similar for SMP and LSM powders, as was the lipid content, ∼0.70 and ∼0.69% for LSM powder
The LSM powder prepared in this study exhibited similar carbohydrate and lipid content to SMP, while its protein content was lower than that of SMP. Similarly to reconstituted skim milk powder (10wt%), LSM exhibited a negative redness (a*) appearance, and its yellowness (b*) at 10wt% was closer to that of 10wt% skim milk. However, the lightness (L*) of LSM, even at 20wt% concentration was darker compared to 10wt% skim milk. The particle size distribution of LSM was multimodal with two main
Zhao Li: Methodology, Investigation, Data curation, Writing - original draft. Tingting Li: Investigation. Meng Zhao: Investigation. Bo Cui: Funding acquisition, Supervision. Yacine Hemar: Methodology, Data curation, Conceptualization, Writing - review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
We would like to thank Dr. Hongshui Lu for his technical support with CLSM experiments. The research was supported by Key Research and Development Program of Shandong Province (No. 2021CXGC010808).
VSI: Fundamentals and application of food hydrocolloids
Food Hydrocolloids, Volume 140, 2023, Article 108610
Insight in changes in starch and proteins molecular structure of non-wheat cereal flours influenced by roasting and extrusion treatments
Food Hydrocolloids, Volume 140, 2023, Article 108591
Barley, rye, triticale, oat, sorghum and millet flours, subjected to roasting or extrusion treatment, were analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) and Raman spectroscopy with aim to determine structural changes within starch and protein molecules that caused specific rheological properties of heat treated flours. Mixolab was used to determine how changes in starch and protein structure are reflected in rheological properties of dough. Extrusion treatment caused more extensive changes both in starch and protein structure than roasting treatment. Changes of protein secondary structure from α-helix to β-turn aggregated by hydrogen bonds, formed mainly between tyrosyl groups, as well as change in disulphide bond conformation, were more pronounced in extruded flour samples. Changes in the starch structure were also more extensive in extruded flours samples, including complete gelatinization and formation of amylose-lipid complexes. The results obtained by Mixolab showed that all extruded doughs showed resistance at C2 point, which was shifted to approximately 30min, indicating higher mechanical resistance. It was supposed that this change in dough behaviour is related to protein polymerization during extrusion treatment and starch aggregation during roasting treatment.
The effect of sodium alginate on the nanomechanical properties and interaction between oil body droplets studied using atomic force microscopy
Food Hydrocolloids, Volume 140, 2023, Article 108587
This study investigates the nanomechanical properties of different oil bodies (OBs), including soybean, peanut, sesame, and rapeseed, coated with sodium alginate (ALG), and the interaction between ALG-coated OBs using atomic force microscopy (AFM). Hooke's law, Reissner theory, and the Membrane model were respectively applied to analyze the nanomechanical properties of the linear and non-linear mechanics of the ALG-coated OBs. It was found that stiffness Kb and modulus ER from the linear deformation of ALG-coated OBs increased with the increase of the ALG layer thickness, while modulus Em from the non-linear deformation was larger than ER and correlated with the compression degree of the ALG layer. The interaction between pure OBs depended on the OB type. Electrostatic interaction which is related to the surface ζ-potential of the OBs occurs at a relatively long interaction distance, while at a relatively short distance, interfacial deformation of OBs occurs and the interaction force is affected by the structure and mechanics of OB interfacial membrane. After coating by ALGs, the electrostatic repulsion occurred from a longer distance than that between pure OBs, and both electrostatic repulsion and steric hindrance exist for a long interaction distance as the ALG-coated OBs continued to approach each other. ALG coating can also weaken the electrostatic screening effect of salt ions, avoiding aggregation of OBs and thus improving their stability. The present work demonstrates the feasibility of using AFM to study the mechanical properties and interaction of OB droplets at the molecular level, and reveals the mechanism of the influence of polysaccharide macromolecules on the stability of OB emulsions from the microscopic scale.
Regulation, production and clinical application of Foods for Special Medical Purposes (FSMPs) in China and relevant application of food hydrocolloids in dysphagia therapy
Food Hydrocolloids, Volume 140, 2023, Article 108613
The development and evolution of regulation, production and clinical application of Foods for Special Medical Purposes (FSMPs) in China in recent decades have been reviewed. The FSMPs as dysphagia diet and relevant applications of food hydrocolloids in FSMPs from the viewpoint of rheology were emphasized. Consumer preference, behaviour and perception about FSMPs were also presented. It is a remarkable transition of the legal status of FSMPs from “drugs” to “foods” in China, just as that in USA and EU, which is marked as a milestone by several important national standards and related laws issued in the last decade. The huge market capacity of FSMPs in China has been estimated based on the number of malnourished patients and elderly consumers. However, the supply of FSMPs from both multinational and local producers has not met the strong demand in China market, even though the State Administration for Market Regulation (SAMR) has approved 92 new products by December 2022. Nevertheless, the market prospect is quite optimistic, based on the profound recognition and widespread clinical application of FSMPs in specific diseases, such as dysphagia, cancer, diabetes, chronic kidney disease, etc.
Encapsulation of salmon oil using complex coacervation: Probing the effect of gum acacia on interfacial tension, coacervation and oxidative stability
Food Hydrocolloids, Volume 140, 2023, Article 108598
The molecular characteristics of the food-grade polysaccharide gum acacia may vary depending on source, which could in turn significantly affect its behaviour as thickener, emulsifier and as a wall material in microencapsulation. In this study, five acacia gums (GA) from different sources were screened with respect to molecular weight distribution, interfacial tension, microencapsulation of salmon oil by complex coacervation and resulting oxidative stability of the oil. Bovine serum albumin (BSA) was used in combination with GA (BSA:GA=1:1 w:w) for the coacervation. Interfacial tension was investigated for all GA alone and in combination with BSA at pH 5.5, pH 4.2 and pH 7, corresponding to the pH of emulsification, coacervation and neutral/reference conditions, respectively. Three of the five GA tested (GA from Sigma and the food grade GA Encapcia and Instant Gum BA from Nexira) resulted in stable complex coacervate microcapsules, with mean coacervate yields of the resulting microcapsules ranging from 34% to 76% depending on GA source, and a ∼100% microencapsulation yield. The food grade GA Encapcia and Instant gum BA were found to provide significantly better protection against oxidation than the Sigma GA, both as a function of the microencapsulation process and after storage for 12 months. The differences in performance of the GA are discussed in terms of molecular weight, GA variety and impurities.
The importance of shear and extensional rheology and tribology as the design tools for developing food thickeners for dysphagia management
Food Hydrocolloids, Volume 140, 2023, Article 108603
Food texture manipulation and modification is a practical strategy to reduce the risk of aspiration for dysphagia management. Addition of thickening agent to thicken liquid can increase the bolus transit time, thus, potentially leading to safer swallowing. The important bolus characteristics for safe swallowing include viscosity, hardness, cohesiveness, and adhesiveness, which can be related to the rheological and tribological properties of bolus. Therefore, this work highlights the importance of shear and extensional rheology and tribology as the design tools for developing dysphagia food thickeners. A range of commercially available thickening powders (xanthan gum-, guar gum-, and modified starch-based) was studied to create baseline rheological and tribological data. In general, it was observed that the increase in thickener concentration led to increases in shear viscosity, viscoelastic properties, and extensional viscosity, but the impact on tribological behavior was varied depending on the type of thickener and lubrication regime. It was also revealed that, at the same liquid consistency based on IDDSI classification, xanthan gum-based thickener showed the highest low shear viscosity, extensional viscosity, and lubricating capacity than the other thickeners. More specifically, modified starch-based thickener showed the poorest extensional property and could be the least effective thickener for promoting safer swallowing. The proposed design tools may be used beneficially to tailor novel thickeners for dysphagia management based on the obtained baseline data. Nonetheless, in-depth knowledge on the relationship between these properties and in-vivo measurements of swallowing is still required and is key to achieve the most effective therapeutic strategy in the dysphagia treatment.
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