Food Biochemistry and Food Processing (2 edition)

BLBS102-c30 BLBS102-Simpson March 21, 2012 13:56 Trim: 276mm X 219mm Printer Name: Yet to Come

586 Part 5: Fruits, Vegetables, and Cereals

is a more accurate measure of unmodified lysine since total ly-

sine determination often includes lysine that has reverted from

modified lysine derivatives (early Maillard products) during

acid hydrolysis. In addition to the formation of unavailable ly-

sine derivatives, it has also been described that the advance

of MR as a result of processing is at least partly responsible

for the reduction in the overall protein digestibility (Rutherfurd

et al. 2006).

Furosine

The determination of furosine (ε-N-2-furoylmethyl-lysine), gen-

erated from the acid hydrolysis of Amadori compounds formed

during the early stages of MR (Erbersdobler and Hupe 1991),

has been used for the assessment of lysine loss in malt

(Molnar-Perl et al. 1986), pasta (Resmini and Pellegrino 1991, ́

Garc ́ıa-Banos et al. 2004, Gallegos-Infante et al. 2010), baby ̃

cereals (Guerra-Hern ́andez and Corzo 1996, Guerra-Hernandez ́

et al. 1999), baby biscuits (Carratu et al. 1993), cookies`

(G ̈okmen et al. 2008a), fibre-enriched breakfast cereals

(Delgado-Andrade et al. 2007), flours employed for the for-

mulation of cereal-based products (Rufian-Henares et al. 2009) ́

and bread (Ram ́ırez-Jim ́enez et al. 2001, C ́ardenas-Ruiz et al.

2004). Other 2-furoylmethyl derivatives such as the ones cor-

responding to GABA (2-FM-GABA) have been, among others,

suggested as indicators of the extent of the MR in different veg-

etable products (Del Castillo et al. 2000, Sanz et al. 2000, 2001,

Soria et al. 2009).

Furosine determination was used by Rada-Mendoza et al.

(2004) to evaluate the advance of MR in commercial cookies,

crackers and breakfast cereals. Furosine was detected in all anal-

ysed samples within a wide range of variation: 25–982 (in cook-

ies), 163–751 (in crackers) and 87–1203 (in cereals) mg/100 g

protein. Figure 30.1 illustrates, as an example, the HPLC chro-

matogram of the 2- FM-amino acids of the acid hydrolysate of

a cereal breakfast sample. Besides furosine, these authors found

2-FM-GABA in samples of crackers and breakfast cereals,

which was absent in most cookie samples analysed. The pres-

ence of 2-FM-GABA in breakfast cereals and crackers may be

attributed to the considerable amount of free GABA present in

rice and corn used in their manufacture.

Recently, Delgado-Andrade et al. (2007) showed that regard-

less of the protein source (i.e., type of cereal), the higher the

protein content, the higher the furosine level of breakfast cereal

formulations. According to this, breakfast cereals enriched in

dietary fibre showed the highest content of this quality marker.

Regarding the physical form of the sample, higher furosine lev-

els were found in puffed cereals as compared to flakes, probably

due to the more pronounced heating during processing.

Contribution of milk components used during breakfast

cereal manufacture to furosine content is still controversial

(Rada-Mendoza et al. 2004, Delgado-Andrade et al. 2007).

Whereas some authors partly attributed the wide variation of

this heat-induced marker to the considerable amounts of furo-

sine in dried milk (Corzo et al. 1994), others concluded that

addition of these components was not directly related to the lev-

els of furosine in the product. The effect of fibre, which was not

taken into account in some of these studies, could be responsible

for the discrepancies observed.

In cookies, furosine formation has been shown to be

highly dependent on the dough formulation and baking con-

ditions (Gokmen et al. 2008a). Therefore, furosine cannot be ̈

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Absorbance

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51015

Time (min)

20

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25 30

Figure 30.1.HPLC chromatogram of the acid hydrolysate of a breakfast cereal sample: (1) 2-furoylmethyl-GABA and (2) furosine (From

Rada-Mendoza et al. 2004).