Mighty mites and mice
Photo 2 camels: Sources of variation in the calorific values of milks from the two species of camels were examined, covering published data over 38 years from 7,236 camel milk samples. Credit: Edwin Vosen/Pexels
The first issue of the 2024 International Journal of Dairy Technology contains two reviews plus 20 reports of original research.
The first review examined sources of variation in the calorific values of milks from the two species of camels, covering published data over 38 years from 7,236 camel milk samples, predominantly from Camelus dromedarius. The effects of species, countries, seasons and year were quantified.
The effects of standardising cheese milk on partitioning of casein and fat in cheddar cheese making were covered in the second review. The simplest method was by separation of cream then re-blending to a desired fat to protein ratio. Better results may be achieved via membrane filtration such as microfiltration for standardisation of the casein to fart ratio.
Milk production
Chlorate can be formed by the degradation of chlorinating agents in water and can affect the thyroid gland, particularly in infants and the young. Thus, the EU limits chlorate residues to less than 0.1 mg/kg, including in liquid milk. A laboratory and on-farm evaluation demonstrated that chlorate contamination of milk could result from admixture with chlorinated water and that it was essential that milk handling plant was designed and operated to avoid the adulteration of milk with water. Chlorate levels in sodium hypochlorite solutions increase with time, adding to potential problems.
A comparison was made between the foremilks and hindmilks from native and crossbred dairy goats. Several factors affecting productivity were identified.
Liquid milk
Less is known about digestion of UHT milks than for pasteurised milks. In vitro digestion of full fat, semi-skimmed and skimmed UHT milks was set up with oral, gastric and small intestine phases. All milks increased in viscosity at the gastric stage with the higher fat formulations exhibiting higher viscosity, faster proteolysis and lipolysis but there was a lower conversion of triglycerides by the end of the intestinal phase.
Cheese and whey
Cheese mites are associated with traditionally ripened cheese and steps are usually taken to minimise their numbers and thus economic loss. To assess the risk of consuming cheese ripened in the presence of mites, an ad libitum feeding plan with non- and immunosuppressed mice was carried out. No detrimental effects of consuming the cheese ripened in the presence of mites were found.
Whey is an inexpensive growth medium for lactose-fermenting organisms. Ectoine production by Halomonas neptunia was maximised using a medium with 50% whey and 10% salt at 30°C with a pH of 6.5 under aerobic shaking.
Plant protein hydrolysates were incorporated into low-fat mozzarella analogues for use in pizzas. Adding 6% soya protein hydrolysate or 4% pea protein hydrolysate to the cheese milk resulted in improved functionality but a less regular microstructure.
Spore forming bacteria such as Bacillus cereus can survive and grow in processed cheese to cause spoilage. A study of processing methods, levels of polyphosphate and storage temperature showed that the creaming process, level of polyphosphate and storage temperature had a significant effect. Raising the level of polyphosphate and storing at 6°C rather than 30°C enhanced the inhibitory effect.
The glycomacropeptide component in whey is relatively low in phenylalanine and was used in production of a goat cheese analogue for those suffering from phenylketonuria.
Processed cheese spreads are usually manufactured on a batch basis. The development of a three litre, small-scale universal batch processor with high shear mixer was reported.
Milk proteins
Oats (Avena sativa) are a relatively rich cereal source of fibre and protein though slightly suboptimal in lysine if the cereal is to be a major part of a diet. The effects of fortifying with whey protein concentrate (WPC), whey lactalbumin concentrate (WLC) or skim milk powder (SMP) on gel strength and hot paste stability were investigated. Substitutions at 5% and 10% reduced gel strength while WPC and WLC increased hot paste stability better than SMP. However, WPC and SMP addition gave more elastic gels than WLC.
Surfactants are widely used in food formulations and tea saponin (TS) is widely found in the seeds of Camelia spp. While such small molecules are better for interfacial adsorption, their foaming and emulsion stability is poorer but this may be improved by complexing with proteins such as a-lactalbumin (a-LA). Simulated in vitro digestion was carried out on an a-LA–TS complex subjected to heat treatments at 65°C/30 minutes and 90°C/10 minutes. The addition of TS increased foaming ability plus radical scavenging ability after digestion and reduced digestibility.
The onset of diabetes is associated with decreased sensitivity to insulin and thus difficulty in regulating blood glucose levels. Treatments include using dipeptidyl peptidase-IV (DDP-IV) inhibitors, which inactivate hormones that inhibit insulin production. These DDP-IV inhibitors are proline-rich peptides, which are present in b-casein hydrolysates. A range of proteases were used to hydrolyse b-casein from Bos indicus and the hydrolysates assayed for DDP-IV inhibition. Protease from Aspergillus oryzae exhibited the highest inhibition and the hydrolysates were characterised and the efficiency of their low molecular weight fractions assessed.
Inability to metabolise phenylalanine (Phe) to tyrosine can lead to phenylketonuria (PKU) in those with that defect and can be avoided by minimising the Phe in the diet. Whey protein was hydrolysed in two stages by trypsin and flavorzyme, followed by adsorption on activated carbon to give an 89.79% reduction.
The carcinogen bisphenol A (PBA) is widely used in production of plastics and resins and can migrate into foodstuffs. Brined white cheeses were produced from raw bovine milk with one batch of milk contaminated by BPA at 1 mg/L. The cheeses were packed in 18% brine in polyethylene terephthalate packages and stored at 4°C for 270 days. BPA levels were very low in the control cheese and in both sets the levels were lower in the brine than in the cheese.
Castellano cheese is a Spanish ovine milk cheese, which may be made from raw or pasteurised milks. Addition of commercial starter cultures enables better regulation of acid development but at the risk of poorer flavour characteristics. Batches of cheese were made from pasteurised milk plus a commercial starter culture, with or without non-starter lactic acid bacteria. The addition of the non-starter lactic acid bacteria improved the flavour and aroma of the cheese.
Fermented milks
Several claims have been made for the use of ultrasound in yogurt production, including for homogenisation, as an alternative to heat treatment and to accelerate fermentation. In this report, ultrasound was used on a small scale at low intensity either before or after inoculation. In both treated groups the levels of volatile flavour compounds were greater than for the control with the level of ketones highest in the milk treated before inoculation.
Lactiplantibacillus plantarum L3 is a potential probiotic for fermented milks. Microencapsulation with modified pectin in a water-in-oil-in-water system with over 96% encapsulation efficiency gave an aerobic plate count of 7.83 log cfu/g after simulated gastrointestinal treatment. Post-acidification of MRS medium was inhibited and the cell-free supernatant had a bacteriostatic effect.
Other products
The Indian dessert Basundi is made by boiling a sweetened milk to 2-3 times concentration, generating a viscous caramelised product similar to Dulce de leche. Ohmic heating at 50Hz and 13.33 V/cm was used and the product made from sweetened buffalo milk had superior sensory properties.
Biscuits suitable for PKU sufferers were produced, using a low-Phe whey protein hydrolysate. The best results were found with the hydrolysate at 15%, giving 0.25 g Phe/100g and 9.1 g protein/100g of biscuit.
Analysis
Textural properties of stretched-curd cheese are closely related to the level of insoluble rather than total calcium in the curd. Direct measurement of insoluble calcium is difficult but can be inferred by deducting water-soluble calcium levels, for instance that lost in whey, from total calcium. A rapid water-soluble calcium extraction was thus evaluated as a rapid insoluble calcium phosphate measure and compared to existing methods. Values for insoluble calcium correlated with meltability of mozzarella stored for one month.
