M. Ross

ABSTRACT Microbial transglutaminase forms nondisulfide covalent crosslinks in proteins and is being used in foods. This enzyme may produce beneficial effects during breadmaking that are comparable to traditional oxidizing improvers, hypothesized to act via formation of disulfide crosslinks. Transglutaminase greatly improved the crumb strength of baked loaves and provides a potential solution to a common consumer complaint. Transglutaminase also reduced the required work input and substantially improved the water absorption of the dough. Each of these effects would lower processing costs for commercial baking

ABSTRACT: Microbial transglutaminase forms nondisulfide covalent crosslinks in proteins and is increasingly being used in foods. We have previously demonstrated beneficial effects of microbial transglutaminase during breadmaking, which are comparable to traditional oxidizing improvers, hypothesized to act via formation of disulfide crosslinks. Transglutaminase substantially improved the lift of puff pastry. It also had a dramatic effect on the volume of yeasted croissants made with both white flour and a blend of wholemeal and white flour. Furthermore, these effects were preserved after the pastry and croissant doughs had undergone frozen storage for periods of up to 90 d. Transglutaminase, therefore, offers a potential solution to the problem of pastry and croissant dough deterioration on frozen storage.

Abstract A novel starch bread that contained no gluten was found to firm at a rate comparable to a normal standard bread made from wheat flour. Treatment of both the starch and the standard bread with Novamyl, an antistaling enzyme mix, inhibited firming. 13 C CP/MAS NMR studies showed that the decreased firming of the Novamyl‐treated starch bread was correlated with decreased starch retrogradation. For the Novamyl‐treated bread the increase in retrograded starch over six days following baking was about 11% compared to an increase of over 200% for the untreated bread. These results suggests that starch retrogradation is sufficient to cause bread firming.

Hypotheses on the role of gluten in bread staling range from gluten having an anti-firming effect, or no effect on firming, to gluten-starch interactions being essential for bread firming. To test these hypotheses, the firming rate of starch bread made from protein-free synthetic flour was compared with that of starch-gluten breads made from synthetic flours containing 1–15% gluten (Fig. 1). Only loaves of similar specific loaf volume and crumb moisture content were compared to eliminate these parameters as variables that might influence firming rate. The starch breads clearly increased in firmness up to six days, indicating that gluten was not essential to the firming process, starch alone causing bread to firm with time. The starch-10% gluten breads and starch-15% gluten breads had very similar specific loaf volumes, moisture contents and firming rates to that of the starch breads. This indicates that protein possibly has some role in firming, because if only starch has a role in firming then adding gluten would effectively dilute the starch and reduce the rate of firming. We propose that increasing bread firmness results from glucan chains of partially leached amylose and amylo-pectin attached to swollen starch granules forming hydrogen bonds with other starch granules and, to a smaller extent, with gluten fibrils.

ABSTRACT Millstream flours, bran, pollard, and germ fractions were prepared from two Australian and two New Zealand wheat cultivars using a pilot‐scale roller mill. The distribution of six redox enzymes in milling fractions and the relationship of the enzymes to baking parameters were investigated. Lipoxygenase (LOX), dehydroascorbate reductase (DAR), and protein disulfide isomerase (PDI) tended to be higher in the tail‐end fractions of break and reduction flour streams, but the highest levels were in the bran, pollard, and germ fractions. These enzymes had moderate to strong correlations with ash content of flour. These results indicated that a considerable amount of these enzymes in the tail‐end flour streams were likely to be derived from contamination with bran, aleurone, or germ components of grain. Peroxidase (POX) tended to be higher in the break flours, but polyphenol oxidase (PPO) and ascorbate oxidase (AOX) tended to be evenly distributed in the millstream flours. These three enzymes generally had poor correlations with ash and baking parameters. LOX and DAR had a negative correlation with the baking quality of bread made in the absence of ascorbic acid (AA) but a poor correlation with improvement of bread quality made with AA. The negative correlation probably reflects the high content of ash (hence trichomes), glutathione, and protein thiols in those fractions that have high LOX and DAR, and these high‐reducing‐power components and trichomes in flour may be the actual cause of poor quality bread. PDI generally had a poor correlation with bread quality in the absence of AA but a significant positive correlation with improvement in the quality of bread made with AA. It thus seems that the endogenous levels of these six enzymes were not a limiting factor in the breadmaking process, except for PDI, the levels of which may have positively influenced breadmaking in the presence of AA.