Application of PTR‐TOF‐MS for the quality assessment of lactose‐free milk: Effect of storage time and employment of different lactase preparations

Abstract

Lactose-free dairy products undergo several chemical modifications during shelf life because of the reactivity of glucose and galactose produced by the lactose enzymatic hydrolysis. In this study, proton transfer reaction-mass spectrometry (PTR-MS), coupled with a time-of-flight (TOF) mass analyzer, was applied to get an insight on the phenomena occurring during the shelf life of ultrahigh-temperature (UHT) lactose-free milk (LFM). UHT LFMs produced by three different commercial lactase preparations were evaluated during storage at 20 C over a 150 days period, sampling the milk every 30 days. Production was repeated three times, on three consecutive weeks, in order to take milk variability into consideration. Principal component analysis applied to the whole "volatilome" data demonstrated the capability of PTR-TOF-MS in detecting the milk batch-to-batch variability: Freshly produced milk samples were distinguished based on the week of production at the beginning of shelf life. Additionally, a clear evolution of the volatiles organic compounds (VOCs) profiling during storage was highlighted. Further statistical analysis confirmed VOCs temporal evolution, mostly because of changes in methyl ketones concentration. Differences caused by the commercial lactases did not emerged, except for benzaldehyde. Altogether, data demonstrated PTR-TOF-MS analysis as a valuable and rapid method for the detection of changes in the VOCs profiling of UHT LFM.

Chemical and sensory changes during shelf-life of UHT hydrolyzed-lactose milk produced by “in batch” system employing different commercial lactase preparations

“…Table 3 summarizes the VOCs measured by HS SPME GC-MS. A total of 22 VOCs matched the spectra of the NIST/Wiley libraries, with several compounds already reported in other published articles on both regular and hydrolyzed-lactose UHT milk (Jansson, Jensen, Eggers, et al, 2014c;Jeon, Thomas, & Reineccius, 1978;Rysstad, Ebbesen, & Eggestad, 1998). The calculated LRIs for each VOC were similar to the one previously reported by our group Bottiroli, Pedrotti, et al, 2020;Bovolenta, et al,2014), as well as to the ones avaiable from the NIST library. Statistically significant differences were found in the VOCs profile of the UHLM produced with the different LPs.…”

Understanding the effect of storage temperature on the quality of semi-skimmed UHT hydrolyzed-lactose milk: an insight on release of free amino acids, formation of volatiles organic compounds and browning

“…An increase in the concentration of methyl ketones, aldehydes and organic acids during storage appeared as major responsible for the development of this sensory defect in UHLM (Bottiroli, Troise, et al, 2020;Jensen et al, 2015). Our group estimated these VOCs in UHLM both by HS SPME GC-MS and PTR-TOF-MS, outlining that off-flavors are created mostly alongside Strecker degradation (Bottiroli, Aprea, Betta, Fogliano, & Gasperi, 2020;Bottiroli, Pedrotti, et al, 2020).…”

“…Manufacturing of UHLM is challenging and operating conditions should be carefully monitored to maintain high quality standards (Bottiroli, Pedrotti, et al, 2020). In general, reactions occurring during UHT processing may alter the sensory profile (especially the flavor) of UHT milk, jeopardizing its acceptability (Jansson et al, 2019;Sunds et al, 2018).…”

Unveiling the Molecular Basis of Mascarpone Cheese Aroma: VOCs analysis by SPME-GC/MS and PTR-ToF-MS

“…Even if preliminary, these results confirm the potential of PTR-TOF-MS analysis for the quality evaluation of lactose-free dairy products. In fact, recently, this analytical approach found application to monitor VOC variability in ultrahigh temperature lactose-free milk samples (assessing the impact of storage time and the of the use of different lactase preparations) [39] 3. Materials and Methods…”