Casein has been shown to be effective post workout. Keep in mind that as far as gastric emptying goes, casein isn't going to delay anything else from even starting to empty by a significant degree. It will take longer for total emptying, but that's not going to happen for a while anyways.
EFFECTS OF WHEY PROTEIN SUPPLEMENTATION WITH CASEIN OR BCAA & GLUTAMINE ON TRAINING ADAPTATIONS I: BODY COMPOSITION
Medicine & Science in Sports & Exercise: Volume 35(5) Supplement 1 May 2003 p S395
This study examined whether whey protein supplementation (fortified with casein [slow digesting protein] or BCAA & glutamine [fast digesting anabolic amino acids]) affects body composition alterations during resistance-training. 44 resistance-trained males (31±8 yrs, 81±16 kg) participated in a standardized 10-week resistance-training program. In a double blind and randomized manner, subjects supplemented their diet with either 48 g/d of a carbohydrate placebo (P); 40 g/d of whey protein + 8 g/d of casein (WC), or 40 g/d of whey protein + 3 g/d BCAA +5 g/d L-glutamine (WBG). At 0, 5, and 10 weeks of supplementation, subjects were weighed and had body composition determined using DEXA. Dietary records were recorded every two weeks. Data were analyzed by repeated measures ANOVA and are presented as means ± SEM changes from baseline. Results revealed no significant differences among groups in total energy intake or training volume. Significant interactions (p < 0.05) were observed among groups in body mass (P 0.2±0.4; WC 1.9±0.7; WBG 0.2±0.5 kg) and fat free mass (P 0.1±0.3; WC 1.8±0.6; WBG 0.0±0.3 kg) with no significant differences observed in fat mass or percent body fat. Post-hoc analysis revealed that subjects who ingested WC experienced greater gains in body mass and fat free mass during training. Results indicate that WBG supplementation during training does not affect body composition alterations in comparison to an isoenergetic carbohydrate placebo. However, WC supplementation promoted greater gains in body mass and FFM possibly due the impact of casein on delaying gastric emptying and/or promoting a more prolonged increase in amino acid levels