Effects of disulphide bonds between added whey protein aggregates and other milk components on the rheological properties of acidified milk model systems

Micro- and nanoparticulated whey protein (MWP, NWP) were added to non-fat milk model systems and processed into chemically (glucono-delta-lactone) acidified milk gels. Model systems contained 5% protein in total and were made at two levels of casein (2.5% and 3.5%, w/w) with and without the thiol-blocking agent N-ethylmaleimide. The systems were characterised in terms of thiol groups, gel electrophoresis, particle size, and rheology during processing (homogenisation, heat treatment and acidification). The results showed that the formation of disulphide-linked structures in milk model systems was closely related to the increased particle size and rheological behaviour of the gels. MWP enriched systems produced, upon acidification, weak protein networks and required the addition of whey protein isolate (WPI) to increase gel strength. However, systems containing NWP exhibited pronounced increase in particle size and higher firmness of acidified gels through both covalent and non-covalent interactions.     

Effect of calcium reduction on the properties of half-fat Cheddar-style cheeses with full-salt or half-salt

Standard-calcium (SCa) and reduced-calcium (RCa) half-fat (16%) Cheddar-style cheeses with full-salt (1.9%) or half-salt (0.9%) were made in triplicate, ripened for 270 d, and analysed for composition and changes in lactose metabolism, pH, proteolysis, water-sorption, fracture properties and heat-induced flowability during maturation. The pressing load applied to the moulded cheese was modified to ensure equal moisture in all cheeses despite the differences in salt and calcium levels. The RCa cheeses were characterised by higher primary proteolysis (α_S1-casein degradation, pH 4.6-soluble N development), lower secondary proteolysis (concentration of free amino acids), higher water-holding capacity on reducing relative humidity from 85 to 5%, lower fracture stress and strain, and more extensive flow on heating. Overall, calcium reduction, when used in conjunction with moisture normalisation, proved an effective means of counteracting the adverse effects of fat reduction on texture and cooking properties in half-fat, half-salt cheese.     

Adoption of cowpea hermetic storage by women in Nigeria,Niger and Burkina Faso

In this study, 2741 randomly selected rural women were interviewed about their cowpea storage practices in 101 villages in Burkina Faso, Niger and Nigeria in late 2010 and early 2011. The overall objective was to determine their cowpea storage practices and identify the most important factors in choosing Purdue Improved Crop Storage (PICS) triple bag storage. About two thirds of women said they used some type of hermetic storage. The hermetic containers included metal drums, plastic jugs, double bags and triple bags. The weighted percentage of women using PICS triple layer bags is 46%. Quantity of cowpea stored by technology showed similar patterns. Overall the percentage of cowpea in hermetic storage was 64%. The study estimated that women stored 50% of their cowpea in PICS bags. The percentage of cowpea in hermetic storage overall and in PICS bags specifically is higher for women than for men in a parallel 2012 ten-country study of mostly male household heads. In PICS villages, the women cite PICS technicians as the most important source of information. In Non-PICS villages, radio was the most important. Most women say that higher income is the major benefit of PICS. The 2009–2010 three country weighted average of the net cash flow from cowpea storage in PICS bags is $10.81/100 kg bag and $39.27 per respondent. Overall, the women indicated that local unavailability was the primary constraint to use of PICS bags. The LOGIT regression analysis shows that the most important factor influencing use of PICS technology is living in a village where PICS demonstrations occurred. The regression shows that radio and the PICS technicians have key roles as information sources. Being able to attend mixed gender meetings was statistically significant only in Burkina Faso where PICS did not organize many women-only PICS activities.     

PARTICLE ADHESION AND REMOVAL: A REVIEW

ABSTRACT

A review is given of the factors playing a role in particle adhesion and removal. The emphasis is put on those systems, which are of colloidal nature (so that gravitational effects can be neglected), and which are as close as possible to the sphere-plate model. It is shown that the major interaction forces are the omni-present van der Waals force of attraction and in an liquid environment, in addition, the electrostatic double layer force of repulsion and, in particularly in a polar liquid, the Lewis acid/base force of interaction, which is responsible for hydrophobic bonding. The magnitude of the various interactions depends on the surface properties of the adherents and on the deviations of the idealized model, such as an extended contact area. The latter is also responsible for alterations with time, either as a result of plastic or elastic deformation.

The removal of particles of colloidal dimensions from a solid surface is controlled by the wall shear stress of the flow passing by, and in case of applying an air-liquid interface by the contact angle of the fluid and the adherents.     

Effect of the use of carbon dioxide on Prato cheese making

The effects of the addition of carbon dioxide (CO₂) under pressure (1.6 × 10⁵ Pa at 8 °C) to pasteurised Prato cheese milk (pH 6.0) was investigated through 120 d of refrigerated storage. The addition of CO₂ decreased the curd formation time (30 min), the total manufacturing time (47 min), and the pH of Prato cheese, thus leading to reduced moisture content. The CO₂ treated cheese showed higher firmness and fracturability due to the greater whey loss. In contrast, the microorganism counts, cheese yield, protein loss, cohesiveness, springiness, and gumminess were not significantly affected by the treatment. For the lactose fermentation, no significant differences were observed. The addition of CO₂ did not change the proteolysis indexes, and no significant differences were observed in the sensory acceptance of the CO₂ treated cheese, which was well accepted by consumers.     

Postharvest processes of edible insects in Africa: A review of processing methods,and the implications for nutrition,safety and new products development

In many African cultures, insects are part of the diet of humans and domesticated animals. Compared to conventional food and feed sources, insects have been associated with a low ecological foot print because fewer natural resources are required for their production. To this end, the Food and Agriculture Organization of the United Nations recognized the role that edible insects can play in improving global food and nutrition security; processing technologies, as well as packaging and storage techniques that improve shelf-life were identified as being crucial. However, knowledge of these aspects in light of nutritional value, safety, and functionality is fragmentary and needs to be consolidated. This review attempts to contribute to this effort by evaluating the available evidence on postharvest processes for edible insects in Africa, with the aim of identifying areas that need research impetus. It further draws attention to potential postharvest technology options for overcoming hurdles associated with utilization of insects for food and feed. A greater research thrust is needed in processing and this can build on traditional knowledge. The focus should be to establish optimal techniques that improve presentation, quality and safety of products, and open possibilities to diversify use of edible insects for other benefits.     

山茱萸发酵乳饮料加工技术研究

研究采用酸牛乳为主要原料,添加白砂糖、山茱萸汁、柠檬酸、香精、增稠剂、乳化剂、螯合剂等辅料,经均质、杀菌、冷却、灌装等加工工艺制成一种保健型含乳饮料。试验结果为:酸牛乳37%、白砂糖10%、山茱萸汁10%、稳定剂0.55%、柠檬酸0.1%~0.2%、柠檬酸钠0.02%、六偏磷酸钠0.03%、香精0.08%,其余为水;加工工艺参数,料液混合温度30℃~40℃、均质条件18~20 MPa、杀菌条件120℃/20 s、在2℃~6℃条件下存放。     

Yoghurt added with Lactobacillus casei and sweetened with natural sweeteners and/or prebiotics: Implications on quality parameters and probiotic survival

The effect of addition of natural sugar substitutes (stevia, erythritol or xylitol) and prebiotics (oligofructose or polydextrose) on physicochemical characteristics, probiotic survival (Lactobacillus casei) and sensory acceptance of yoghurts during storage (7 °C, 28 days) was evaluated. Yoghurts with sucrose or sucralose were also prepared. Xylitol and sucralose added yoghurts had physicochemical characteristics and sensory acceptance similar to those of the product with sucrose. Xylitol was more efficient in maintenance of textural characteristics and probiotic survival in simulated gastrointestinal conditions (SGIC) than sucralose. Addition of erythritol and stevia changed the textural parameters, reduced acceptance and decreased probiotic survival in SGIC. Addition of oligofructose or polydextrose improved texture and increased probiotic survival but decreased flavour acceptance. All formulations could be considered probiotic products during shelf life (7 °C, 28 days) with counts higher than 10⁷ cfu mL⁻¹ in the product and 10⁴ cfu mL⁻¹ after SGIC.