Chemistry Reference
In-Depth Information
hydrocarbons, aldehydes, ketones, alcohols, fatty acids, esters, furans,
phenolic compounds, lactones and nitrogenous compounds, which con-
stituted over 99.5% of the total volatiles recovered. Results obtained
showed that the levels of flavour compounds in the skim milk powder
were very low and that their compositions were extremely complicated.
Among them, free fatty acids and lactones, which were present at relatively
high levels, were considered to be fundamental contributors to the flavour
of skim milk. Moreover, aldehydes, aromatic hydrocarbons and some
heterocyclic compounds, such as indoles or thiazole, seem to participate
indirectly in the flavour of skim milk.
The aroma of dried milk products, such as non-fat dry milk, with
varying heat treatment, involves very similar compounds as shown in
Table 14.4, but the high heat-treated non-fat dried milk particularly has
a strong aroma intensity caused by HDMF, butanoic acid, methional, o-
aminoacetophenone, trans-4,5-epoxy-(E)-2-decenal, sotolon and vanillin
(Karagul-Yuceer et al., 2001, 2003a). A stored sample of non-fat dried
milk had particularly high odour intensities for methional and o-amino-
acetophenone (Table 14.4; Karagul-Yuceer et al., 2002). The odorant
profile of whole milk powder showed a significant effect of the season, as
monitored by the levels of compounds such as dimethyl sulphide, penta-
nal, hexanal and butanoic acid (Biolatto et al., 2007). Whole milk powder
manufactured in summer had significantly higher levels of hexanal, pen-
tanal and dimethyl sulphide as compared to autumn and winter samples.
On the other hand, butanoic acid showed significant differences between
autumn and spring.
Other dried products such as rennet casein, an important food ingre-
dient, particularly suffer from off-flavour. Results of AEDA indicated
o-aminoacetophenone to be a potent odorant; however, descriptive sensory
analysis of model aroma systems revealed that the typical odour of rennet
casein was caused principally by hexanoic acid, indole, guaiacol and p-cresol
(Karagul-Yuceer et al., 2003c). It is essential for rennet casein to be bland and
free of any off-flavour for its use as a food ingredient.
Dried whey and dried whey products are important ingredients in the
food industry. Liquid whey is further processed into dried whey powder,
whey protein concentrates (WPC; 35-80% protein) and whey protein iso-
lates (WPI;
>
90% protein). Dried whey proteins are commonly used
as ingredients due to their exceptional functional characteristics (Morr
and Foegeding, 1990) and nutritional value (Quach et al., 1999). From
the literature, a somewhat vague description of dried and liquid whey
flavour can be obtained. Based on US standards for dry whey (USDA,
2000), reconstituted whey should have a normal liquid whey flavour, free
from undesirable flavours. Characteristically, cheese whey has a slightly
