Lactose Hydrolysis by Fungal and Yeast Lactase: Influence on Freezing Point and Dipping Characteristics of Ice Cream

Matak, Kristen E.

Lactose Hydrolysis by Fungal and Yeast Lactase: Influence on Freezing Point and Dipping Characteristics of Ice Cream

dc.contributor.author	Matak, Kristen E.	en
dc.contributor.committeechair	Duncan, Susan E.	en
dc.contributor.committeemember	Hackney, Cameron Raj	en
dc.contributor.committeemember	Wilson, James H.	en
dc.contributor.committeemember	Sumner, Susan S.	en
dc.contributor.department	Food Science and Technology	en
dc.date.accessioned	2014-03-14T20:30:57Z	en
dc.date.adate	1999-01-19	en
dc.date.available	2014-03-14T20:30:57Z	en
dc.date.issued	1999-01-11	en
dc.date.rdate	2000-01-19	en
dc.date.sdate	1999-01-19	en
dc.description.abstract	Two studies were conducted to examine the effects of lactose hydrolysis on freezing point and dipping characteristics of ice cream. The overall research objective was to determine changes in freezing point, texture and ease of dipping ice cream as a result of lactose hydrolysis. It was also the goal of this research to relate observations from the sensory dippability study with hardness and yield stress data to determine if the latter methods could be used as an alternative to human testing of dippability. In the first experiment, ice cream mixes were treated with lactase (EC 3.2.1.23) to cause 0 to 83% lactose hydrolysis. Lactose hydrolysis decreased the freezing point from -1.63oC in the control (0% hydrolysis) to -1.74oC in the 83% hydrolyzed sample (p < 0.05). Firmness decreased from 0.35 J in the control sample to 0.08 J in the 83% hydrolyzed sample. Lactose hydrolyzed samples melted at a faster rate than the control. There was a difference (p < 0.05) in ease of dipping between samples treated with lactase and the control. There were no perceived differences in sweetness and coldness. In the second study, ice cream mixes were treated with lactase (EC 3.2.1.23) from the microbial sources Kluyveromyces lactis and Aspergillus oryzae to cause 0 to 100% lactose hydrolysis. Compression measurements and yield stress as measured by the vane method were both affected by the temperature of the samples. R2 values for compression measurements as related to lactose hydrolysis were higher then those obtained for yield stress measurements. Human evaluation determined a difference (p < 0.05) between the control samples (0% hydrolyzed) and the treatment groups (80% and 100% hydrolyzed). This research demonstrated a relationship between lactose hydrolysis and ease of dipping ice cream. The results implied that the effect of lactose hydrolysis on the dipping characteristics could be evaluated successfully by three different methods: the vane method, compression measurements, and human evaluation. Changes in freezing point due to lactose hydrolysis were minimal, implying that monitoring freezing point is not enough to determine textural characteristics.	en
dc.description.degree	Master of Science	en
dc.identifier.other	etd-011999-135521	en
dc.identifier.sourceurl	http://scholar.lib.vt.edu/theses/available/etd-011999-135521/	en
dc.identifier.uri	http://hdl.handle.net/10919/30998	en
dc.publisher	Virginia Tech	en
dc.relation.haspart	EDT1TP.PDF	en
dc.relation.haspart	EDT2.PDF	en
dc.relation.haspart	EDT3.PDF	en
dc.rights	In Copyright	en
dc.rights.uri	http://rightsstatements.org/vocab/InC/1.0/	en
dc.subject	vane method	en
dc.subject	freezing point depression	en
dc.subject	ice cream	en
dc.subject	lactose hydrolysis	en
dc.subject	dipping	en
dc.title	Lactose Hydrolysis by Fungal and Yeast Lactase: Influence on Freezing Point and Dipping Characteristics of Ice Cream	en
dc.type	Thesis	en
thesis.degree.discipline	Food Science and Technology	en
thesis.degree.grantor	Virginia Polytechnic Institute and State University	en
thesis.degree.level	masters	en
thesis.degree.name	Master of Science	en