Lactose-free Dairy Products Research Articles

Determination of residual lactose in lactose-free cow milk by hydrophilic interaction liquid chromatography (HILIC) coupled to tandem mass spectrometry

Lactose is the major carbohydrate found in milk and dairy products. Lactose intolerance means the body cannot digest foods with this natural sugar in them. In this context, the lactose-free market has experienced a steep increase in recent years. A new method for the determination of residual lactose in lactose-free dairy products using liquid chromatography coupled to tandem mass spectrometry triple quadrupole (HPLC–MS/MS) has been developed. Hydrophilic interaction chromatography (HILIC) has been used for this purpose. An amide chromatographic column with an alkaline mobile phase were selected as optimal. In addition, a fast, cost-effective and reliable sample treatment has been developed for routine analytical laboratory use. The method has been validated by using matrix-matched calibration standards and a recovery assay on a lactose-free milk sample obtained by lactase hydrolysis of regular milk. The limit of quantification (LOQ) was 15mgL−1, while the recovery was close to 100% with relative standard deviation lower than 9% in all cases. The method was applied to several lactose-free products and the results showed that lactose values in these products are not always below the recommended maximum value of 100mgL−1.

Preparation and characterization of gellan gum microspheres containing a cold-adapted β-galactosidase from Rahnella sp. R3

R-β-Gal is a cold-adapted β-galactosidase that is able to hydrolyze lactose and has the potential to produce low-lactose or lactose-free dairy products at low temperatures (4°C). Cold-adapted enzymes unfold at moderate temperatures due to the lower intramolecular stabilizing interactions necessary for flexibility at low temperatures. To increase stability and usage-performance, R-β-Gal was encapsulated in gellan gum by injecting an aqueous solution into two different hardening solutions (10mM CaCl2 or 10mM MgCl2). Enzyme characteristics of both free and encapsulated R-β-Gal were carried out, and the different effects of two cations were investigated. R-β-Gal showed better thermal and pH stability after encapsulation. Ca2+ gels had higher encapsulation efficiency (71.4%) than Mg2+ (66.7%) gels, and Ca2+ formed larger inner and surface pores. R-β-Gal was released from the Ca2+ hydrogel beads more rapidly than the Mg2+ hydrogels during storage in aqueous solution due to the larger inner/surface pores of the matrix.

Fermented milk products: effects of lactose hydrolysis and fermentation conditions on the rheological properties

Lactose-free dairy products become increasingly important for lactose-intolerant consumers, but there are only few studies concerning the rheological properties of fermented dairy products from lactose-hydrolysed milk. Hydrolysation was performed with commercial β-galactosidase either before or during fermentation (co-hydrolysis). In each trial, fermentation of the base milk was carried out simultaneously using the same starter cultures for (a) untreated milk (reference) (b) hydrolysed milk as substrate and (c) by performing lactose hydrolysis and fermentation simultaneously (co-hydrolysis). In total, five thermophilic starter cultures and two products (yoghurt and Greek-style yoghurt) were investigated. Results show that the influence of hydrolysis of lactose on the properties of the fermented dairy products strongly depends on starter culture and substrate. For starters C and D, apparent viscosity (extracted from flow curves at a shear rate of 75 s−1) of fermented milks was only marginally affected by lactose hydrolysis, ranging between approx. 0.34–0.31 and 0.37–0.31 Pa.s, respectively. Hydrolysed products from starters A and E exhibited significant lower apparent viscosity (0.16 and 0.24 Pa.s) compared with their respective references (0.29 and 0.35 Pa.s). Fermentation of both substrates (regular yoghurt, Greek-style yoghurt) with starter B resulted in a decrease of yield stress and apparent viscosity because of lactose hydrolysis only for Greek-style yoghurt. Furthermore, a trend towards higher EPS synthesis was found when using hydrolysed milk. The results clearly show that products made from lactose-hydrolysed milk with similar rheological properties as the reference product can be obtained but that there is a lack of information concerning the complex interactions between starter culture and milk substrate.

Streamlined analysis of lactose-free dairy products

Functional food for lactose-intolerant consumers and its global prevalence has created a large market for commercially available lactose-free food products. The simplest approach for detection and quantitation of lactose in lactose-free dairy products was developed. A one-step sample preparation was employed and the resulting 10% sample solution was directly subjected to the chromatographic system. LODs down to 0.04mg/L were obtained for dairy products by application volumes up to 250μL on a rectangular start zone, which is the lowest LOD reported in matrix so far. The highly matrix-robust, streamlined approach was demonstrated for a broad range of dairy products, even with high fat and protein contents. The mean recovery rate for 11 types of dairy products spiked at the strictest lactose content discussed (0.01%) was 90.5±10.5% (n=11). The mean repeatability for 11 dairy products spiked at the 0.01% level was 1.3±1.0% (n=11). It is the simplest approach with regard to sample preparation at low running costs (0.3 Euro or 0.4 USD/analysis) and fast analysis time (3min/analysis). It enabled an efficient product screening, and at the same time, the quantitation of lactose in relevant samples. This streamlined analysis is highly attractive to the field of food safety and quality control of lactose-free dairy products, for which a limit value for lactose is expected soon in the EU. This methodological concept can be transferred to other challenging fields.

Layer by Layer Assembly of a Biocatalytic Packaging Film: Lactase covalently Bound to Low‐Density Polyethylene

Active packaging is utilized to overcome limitations of traditional processing to enhance the health, safety, economics, and shelf life of foods. Active packaging employs active components to interact with food constituents to give a desired effect. Herein we describe the development of an active package in which lactase is covalently attached to low-density polyethylene (LDPE) for in-package production of lactose-free dairy products. The specific goal of this work is to increase the total protein content loading onto LDPE using layer by layer (LbL) deposition, alternating polyethylenimine, glutaraldehyde (GL), and lactase, to enhance the overall activity of covalently attached lactase. The films were successfully oxidized via ultraviolet light, functionalized with polyethylenimine and glutaraldehyde, and layered with immobilized purified lactase. The total protein content increased with each additional layer of conjugated lactase, the 5-layer sample reaching up to 1.3 μg/cm2 . However, the increase in total protein did not lend to an increase in overall lactase activity. Calculated apparent Km indicated the affinity of immobilized lactase to substrate remains unchanged when compared to free lactase. Calculated apparent turnover numbers (kcat ) showed with each layer of attached lactase, a decrease in substrate turnover was experienced when compared to free lactase; with a decrease from 128.43 to 4.76 s(-1) for a 5-layer conjugation. Our results indicate that while LbL attachment of lactase to LDPE successfully increases total protein mass of the bulk material, the adverse impact in enzyme efficiency may limit the application of LbL immobilization chemistry for bioactive packaging use.

Effects of a fibre-enriched milk drink on insulin and glucose levels in healthy subjects

BackgroundThe glycaemic response to foods is dependent on the quality and content of carbohydrates. Carbohydrates in the form of dietary fibre have favourable effects on insulin and glucose metabolism and may help to control energy intake. Dairy products have a relatively low carbohydrate content, and most of the carbohydrate is in the form of lactose which causes gastrointestinal symptoms in part of the population. In order to avoid these symptoms, dairy products can be replaced with lactose-free dairy products which are on the market in many parts of the world. However, the effects of lactose-free products on insulin and glucose metabolism have not been studied.MethodsIn the present study, we investigated the effects of 1) a lactose-free milk drink, 2) a novel fibre-enriched, fat- and lactose-free milk drink and 3) normal fat-free milk on serum glucose and insulin levels and satiety using a randomized block design. Following an overnight fast, 26 healthy volunteers ingested 200 ml of one of these drinks on three non-consecutive days. Insulin and glucose levels and subjective satiety ratings were measured before the ingestion of the milk product and 20, 40, 60, 120 and 180 minutes after ingestion. The responses were calculated as the area under the curve subtracted by the baseline value (AUC minus baseline).ResultsThe insulin response was significantly lower for the fibre-enriched milk drink than it was for the other milk products (AUC, P = 0.007). There were no differences in the response for glucose or in the AUC for the subjective satiety ratings between the studied milk products.ConclusionThe present results suggest that this novel milk drink could have positive effects on insulin response.

Sensory characteristics of commercial lactose-free milks manufactured in the United States

This study determined the sensory characteristics of ultrapasteurized (UP) lactose-free milk of different fat contents, and compared them with regular milk. Nine milk samples (six UP lactose-free and three regular) containing 0, 2 or 3 g milkfat/100 mL were tested by a descriptive panel. A consumer test with three UP lactose-free milk and three regular samples was also conducted. The skim milks were found to be lacking in freshness and the dairy notes were lower compared to the higher-fat-content milks. The UP lactose-free milks were different from the regular milk because of higher intensities of cooked, processed, and sweet attributes. UP lactose-free milks tended to score higher than the regular milks at the same fat content for dairy-related attributes, but this difference was not significant for the reduced-fat milks. Although majority of the consumers in the present study were aware that UP lactose-free milks existed in the market, only few had tasted them before. The higher intensities of cooked and sweet flavor attributes in the UP lactose-free milks might be a hindrance to their consumption by the lactose-intolerant population. More efforts are needed from the dairy industry to develop better lactose-free products and to educate consumers about lactose-free dairy products.