Effect of ultra-high-pressure homogenization at moderate inlet temperatures on volatile profile of milk

Functional properties and flavor characteristics of milk from cows supplemented with jujube powder

Jujube has various functional properties and is a promising source of bioactive compounds and flavors. This study investigated the functional properties and flavor characteristics of milk from cows supplemented with jujube powder (JP). Here, milk volatile profiles and taste properties were analyzed by using an electronic nose and headspace solid-phase microextraction GC-MS. Compared with the control group, the total antioxidant capacity, 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic free-radical-scavenging activity, lactoferrin, and IgG levels increased significantly in the JP group. Volatile flavor analysis indicated that ketone levels increased, acid abundance decreased, and toluene and dimethyl sulfone significantly increased in the JP group. Taste-profile analyses demonstrated that jujube supplementation altered the taste of the milk. In summary, dietary JP supplementation affects the volatile flavor composition and aroma of milk, as well as the bioactive components and antioxidant properties. These findings enhance our understanding of milk production using direct dietary supplementation to produce sustainable dairy products.

Analysis of Volatile Organic Compounds in Milk during Heat Treatment Based on E-Nose, E-Tongue and HS-SPME-GC-MS

Volatile organic compounds (VOCs) make up milk flavor and are essential attributes for consumers to evaluate milk quality. In order to investigate the influence of heat treatment on the VOCs of milk, electronic nose (E-nose), electronic tongue (E-tongue) and headspace solid-phase microextraction (HS-SPME)-gas chromatography-mass spectrometry (GC-MS) technology were used to evaluate the changes in VOCs in milk during 65 °C heat treatment and 135 °C heat treatment. The E-nose revealed differences in the overall flavor of milk, and the overall flavor performance of milk after heat treatment at 65 °C for 30 min is similar to that of raw milk, which can maximize the preservation of the original taste of milk. However, both were significantly different to the 135 °C-treated milk. The E-tongue results showed that the different processing techniques significantly affected taste presentation. In terms of taste performance, the sweetness of raw milk was more prominent, the saltiness of milk treated at 65 °C was more prominent, and the bitterness of milk treated at 135 °C was more prominent. The results of HS-SPME-GC-MS showed that a total of 43 VOCs were identified in the three types of milk-5 aldehydes, 8 alcohols, 4 ketones, 3 esters, 13 acids, 8 hydrocarbons, 1 nitrogenous compound, and 1 phenol. The amount of acid compounds was dramatically reduced as the heat treatment temperature rose, while ketones, esters, and hydrocarbons were encouraged to accumulate instead. Furfural, 2-heptanone, 2-undecanone, 2-furanmethanol, pentanoic acid ethyl ester, 5-octanolide, and 4,7-dimethyl-undecane can be used as the characteristic VOCs of milk treated at 135 °C. Our study provides new evidence for differences in VOCs produced during milk processing and insights into quality control during milk production.

Preservation of high pressure pasteurised milk by hyperbaric storage at room temperature versus refrigeration on inoculated microorganisms, fatty acids, volatile compounds and lipid oxidation

High pressure pasteurised (HPP) milk was stored by hyperbaric storage at room temperature (HS/RT) (50-100 MPa at 20 °C) and compared with refrigeration (RF), to assess the effect on two pathogens surrogates and a pathogenic, up to 120 days, and on fatty acids, volatile organic compounds (VOCs) and secondary lipid oxidation over 60 days. HS/RT (75-100 MPa) was able to inactivate at least 6.68/6.31/6.03 log CFU/mL of Escherichia coli/Listeria innocua/Salmonella Senftenberg (to below the detection limit), while RF resulted only in minor changes. Overall, fatty acids profile remained stable under HS/RT, although secondary lipid oxidation showed slightly higher values. In addition, both HS/RT and RF showed stable and similar VOCs profiles and off-flavour indicative compounds were not detected, except for the lowest pressure (50 MPa) after 40 days. HS/RT preserved HPP milk with enhanced microbial safety, shelf-life and quality compared to RF, being in addition quasi-energetically costless and more sustainable than RF.

Role of Pascalization in Milk Processing and Preservation: A Potential Alternative towards Sustainable Food Processing

Renewed technology has created a demand for foods which are natural in taste, minimally processed, and safe for consumption. Although thermal processing, such as pasteurization and sterilization, effectively limits pathogenic bacteria, it alters the aroma, flavor, and structural properties of milk and milk products. Nonthermal technologies have been used as an alternative to traditional thermal processing technology and have the ability to provide safe and healthy dairy products without affecting their nutritional composition and organoleptic properties. Other than nonthermal technologies, infrared spectroscopy is a nondestructive technique and may also be used for predicting the shelf life and microbial loads in milk. This review explains the role of pascalization or nonthermal techniques such as high-pressure processing (HPP), pulsed electric field (PEF), ultrasound (US), ultraviolet (UV), cold plasma treatment, membrane filtration, micro fluidization, and infrared spectroscopy in milk processing and preservation.

Short communication: Volatiles in microfluidized raw and heat-treated milk

As innovative processing equipment is introduced to milk processing, it is essential to determine its effect on milk aroma, a critical factor in consumer acceptance of the final dairy product. Microfluidization is known to cause severe high-pressure homogenization of milk fat and, although severe processing is known to release undesired aromas, no information is available on the levels of the volatile compounds in milk immediately after microfluidization. We hypothesized that microfluidization would alter levels of volatile compounds in milk that may affect aroma. The concentration of 11 selected volatile compounds in raw, thermized, pasteurized, and UHT 3.0% fat milk samples were compared before and after microfluidization at 170 MPa and common 2-stage homogenization at 15 MPa. Overall, the different milk samples had similar trends in response to homogenization, although UHT milk started with lower values of nonanoic acid, and acetone and higher levels of hexanal and heptanol. In many cases, microfluidization did not significantly alter volatile levels compared with the starting milk. Heptanal was the only compound observed to increase in thermized and UHT milk, whereas nonanoic acid and acetone decreased in raw, thermized, and pasteurized milks and octanoic acid decreased in thermized and UHT milks. The highest levels of almost all of the volatiles were found in the 2-stage homogenized milk. Overall, microfluidization had minimal effect on the volatile compound profiles of milk, although sensory evaluation is needed to confirm effects on aroma and flavor.